Beneficial associations of physical activity with 2-h but not fasting blood glucose in Australian adults: the AusDiab study

Ethnic-specific oral glucose tolerance (OGTT) phenotypes in women with hyperglycemia in pregnancy

INTRODUCTION

Ethnic differences associated with oral glucose tolerance test (OGTT) phenotypes is less studied in Southeast Asian ethnicities, especially in women with hyperglycemia in pregnancy (HIP).

RESEARCH DESIGN AND METHODS

We retrospectively examined 3027 women at KK Women's and Children's Hospital in 2019. Of these, 508 (16.8%) women were diagnosed with HIP using the IADPSG (International Association of Diabetes and Pregnancy Study Groups) criteria at 24-28 weeks. OGTT phenotypes were classified into four mutually exclusive groups based on abnormal plasma glucose at (1) 0 hour only; (2) 1 hour only; (3) 2 hour only; (4) ≥2 timepoints (reference). Multinomial logistic regression was used to examine the association between ethnicity and OGTT phenotypes, adjusting for maternal age, parity, and first-trimester body mass index.

RESULTS

Overall HIP prevalence was 16.8%, highest among Indians (20.5%), then Chinese (18.3%) and Malays (14.2%). Indians (relative risk ratio (RRR) 3.05) and Chinese (RRR 2.33) were at higher risk of displaying a fasting-only phenotype compared with Malays. Chinese were at increased risk of displaying a 2-hour postprandial phenotype with an RRR of 2.88 as compared with Malays.

CONCLUSIONS

Unique OGTT phenotypes exist across ethnic groups among women who developed HIP in a multi-ethnic Asian population.

Metabolic phenotyping of BMI to characterize cardiometabolic risk: evidence from large population-based cohorts

Obesity is a risk factor for type 2 diabetes and cardiovascular disease. However, a substantial proportion of patients with these conditions have a seemingly normal body mass index (BMI). Conversely, not all obese individuals present with metabolic disorders giving rise to the concept of "metabolically healthy obese". We use lipidomic-based models for BMI to calculate a metabolic BMI score (mBMI) as a measure of metabolic dysregulation associated with obesity. Using the difference between mBMI and BMI (mBMIΔ), we identify individuals with a similar BMI but differing in their metabolic health and disease risk profiles. Exercise and diet associate with mBMIΔ suggesting the ability to modify mBMI with lifestyle intervention. Our findings show that, the mBMI score captures information on metabolic dysregulation that is independent of the measured BMI and so provides an opportunity to assess metabolic health to identify "at risk" individuals for targeted intervention and monitoring.

Physical activity and sedentary behavior show distinct associations with tissue-specific insulin sensitivity in adults with overweight

AIM

The aim of this study is to investigate associations between the physical activity (PA) spectrum (sedentary behavior to exercise) and tissue-specific insulin resistance (IR).

METHODS

We included 219 participants for analysis (median [IQR]: 61 [55; 67] years, BMI 29.6 [26.9; 32.0] kg/m² ; 60% female) with predominant muscle or liver IR, as determined using a 7-point oral glucose tolerance test (OGTT). PA and sedentary behavior were measured objectively (ActivPAL) across 7 days. Context-specific PA was assessed with the Baecke questionnaire. Multiple linear regression models (adjustments include age, sex, BMI, site, season, retirement, and dietary intake) were used to determine associations between the PA spectrum and hepatic insulin resistance index (HIRI), muscle insulin sensitivity index (MISI) and whole-body IR (HOMA-IR, Matsuda index).

RESULTS

In fully adjusted models, objectively measured total PA (standardized regression coefficient β = 0.17, p = 0.020), light-intensity PA (β = 0.15, p = 0.045) and moderate-to-vigorous intensity PA (β = 0.13, p = 0.048) were independently associated with Matsuda index, but not HOMA-IR (p > 0.05). A higher questionnaire-derived sport index and leisure index were associated with significantly lower whole-body IR (Matsuda, HOMA-IR) in men but not in women. Results varied across tissues: more time spent sedentary (β = -0.24, p = 0.045) and a higher leisure index (β = 0.14, p = 0.034) were respectively negatively and positively associated with MISI, but not HIRI. A higher sport index was associated with lower HIRI (β = -0.30, p = 0.007, in men only).

CONCLUSION

While we confirm a beneficial association between PA and whole-body IR, our findings indicate that associations between the PA spectrum and IR seem distinct depending on the primary site of insulin resistance (muscle or liver).

Risk stratification of women with gestational diabetes mellitus using mutually exclusive categories based on the International Association of Diabetes and Pregnancy Study Groups criteria for the development of postpartum dysglycaemia: a retrospective cohort study

OBJECTIVES

Women with gestational diabetes mellitus (GDM) are more predisposed to develop postpartum diabetes mellitus (DM). This study aimed to estimate the relative risk (RR) of postpartum dysglycaemia (prediabetes and DM) using mutually exclusive categories according to the International Association of Diabetes and Pregnancy Study Groups (IADPSG) criteria cut-off points in patients with GDM, so as to establish a risk-stratification method for developing GDM management strategies.

DESIGN, SETTING AND PARTICIPANTS

In this retrospective cohort study, 942 women who had been diagnosed with GDM (IADPSG criteria) at 24-28 weeks of gestation from November 2016 to April 2018 underwent a 75 g oral glucose tolerance test (OGTT) at 6-12 weeks postpartum in a tertiary hospital of Singapore. Seven mutually exclusive categories (three one timepoint positive categories (fasting, 1 hour and 2 hours), three two timepoint positive categories (fasting+1 hour, fasting+2 hours and 1 hour+2 hours) and one three timepoint positive category (fasting+1 hour+2 hours)) were derived from the three timepoint antenatal OGTT according to the IADPSG criteria. To calculate the RRs of postpartum dysglyceamia of each mutually exclusive group, logistic regression was applied.

RESULTS

924 mothers with GDM, whose mean age was 32.7±4.7 years, were mainly composed of Chinese (45.4%), Malay (21.7%) and Indian (14.3%) ethnicity. The total prevalence of postnatal dysglycaemia was 16.7% at 6-12 weeks postpartum. Stratifying subjects into seven mutually exclusive categories, the RRs of the one-time, two-time and three-time positive groups of the antenatal OGTT test were 1.0 (Ref.), 2.0 (95% CI=1.3 to 3.1; p=0.001) and 6.7 (95% CI=4.1 to 10.9; p<0.001), respectively, which could be used to categorise patients with GDM into low-risk, intermediate-risk and high-risk group.

CONCLUSIONS

Mutually exclusive categories could be useful for risk stratification and early management of patients with prenatal GDM. It is plausible and can be easily translated into clinical practice.

Comparing the effects of 12 months aerobic exercise and resistance training on glucose metabolism among prediabetes phenotype: A explorative randomized controlled trial

AIMS

The pathophysiology of each phenotype of prediabetes is unique that promotes different levels of diabetes and cardiovascular disease risks. Exercise guidelines for individuals with prediabetes including both aerobic and resistance training could improve metabolic control, but its effects on different prediabetes subtypes are unclear. The aim of this explorative randomized controlled trial was to evaluate the effects of aerobic training (AT) or resistance training (RT) on glucose metabolism and lipid profile by different prediabetes subtypes with.

METHODS

A randomized controlled trial in which 128 individuals with isolated impaired fasting glucose (i-IFG; n = 39), isolated impaired glucose tolerance (i-IGT; n = 29), combined glucose tolerance (CGI; n = 27) and isolated elevated HbA_1c (n = 33) were randomly assigned to the control group, AT group and RT group, respectively. Supervised exercise training, including AT and RT were completed at moderate intensity for 60 min per day, three non-consecutive days per week for 12 months. The primary outcome was improvement in glucose metabolism. Secondary outcomes included measure of lipid profile and if these effects were moderated by the prediabetes phenotype.

RESULTS

Of the initial 128 participants, 118 finished the study, but all participants were included in the intention-to-treat analyses. The improvement in 2 h postprandial plasma glucose (2 hPG) between group difference (AT vs. RT) at 12 months was 0.87 (95% CI, -1.59 to-0.16; p < 0.05). Compared with RT group, AT significantly decreased the 2hPG in participants with i-IGT at 12 months (-1.66, 95% CI -3.04 to -0.28; p < 0.05).

CONCLUSIONS

AT program conferred benefits in improving 2 h PG and HbA_1c compared with RT for prediabetes. These findings may moderate by prediabetes phenotype, and AT appeared more effective in i-IGT. A future trial with large sample size and long time follow up of prediabetes phenotype groups are needed.

Benefit of lifestyle-based T2DM prevention is influenced by prediabetes phenotype

The prevention of type 2 diabetes mellitus (T2DM) is a target priority for the WHO and the United Nations and is a key priority in the 2018 Berlin Declaration, which is a global call for early actions related to T2DM. Health-care policies advocate that individuals at high risk of developing T2DM undertake lifestyle modification, irrespective of whether the prediabetes phenotype is defined by hyperglycaemia in the postprandial state (impaired glucose tolerance) and/or fasting state (impaired fasting glucose) or by intermediate HbA_1c levels. However, current evidence indicates that diabetes prevention programmes based on lifestyle change have not been successful in preventing T2DM in individuals with isolated impaired fasting glucose. We propose that further research is needed to identify effective lifestyle interventions for individuals with isolated impaired fasting glucose. Furthermore, we call for the identification of innovative approaches that better identify people with impaired glucose tolerance, who benefit from the currently available lifestyle-based diabetes prevention programmes.

Association of Habitual Daily Physical Activity With Glucose Tolerance and β-Cell Function in Adults With Impaired Glucose Tolerance or Recently Diagnosed Type 2 Diabetes From the Restoring Insulin Secretion (RISE) Study

OBJECTIVE

We examined the relationship between habitual daily physical activity and measures of glucose tolerance, insulin sensitivity, and β-cell responses in adults with impaired glucose tolerance (IGT) or drug-naive, recently diagnosed type 2 diabetes.

RESEARCH DESIGN AND METHODS

Participants included 230 adults (mean ± SD age 54.5 ± 8.5 years, BMI 35 ± 5.5 kg/m²; 42.6% women) who underwent a 3-h oral glucose tolerance test (OGTT) and hyperglycemic clamp. Wrist accelerometers worn for 7 consecutive days measured total physical activity counts (TAC) (daily mean 233,460 [∼50th percentile for age]). We evaluated whether TAC was associated with fasting plasma glucose, OGTT 2-h plasma glucose or glucose incremental area under the curve (G-iAUC), hyperglycemic clamp measures of insulin sensitivity (steady-state glucose infusion rate/insulin [M/I]) and β-cell responses (acute C-peptide response to glucose, steady-state C-peptide, and maximal β-cell response), and OGTT C-peptide index (ΔC-peptide_0-30/Δglucose_0-30).

RESULTS

After adjustments for confounders, there was no association of TAC with fasting plasma glucose, 2-h glucose, or G-iAUC. Higher TAC was associated with higher insulin sensitivity (M/I). After adjusting for M/I, higher TAC was not associated with measures of β-cell response.

CONCLUSIONS

In adults with IGT or drug-naive, recently diagnosed type 2 diabetes, higher levels of habitual physical activity are associated with higher insulin sensitivity. Further studies are needed to understand why higher levels of physical activity are not associated with better β-cell response.

Effective Weight Loss and Maintenance by Intensive Start with Diet and Exercise

INTRODUCTION

This 24-month study aimed to determine whether exercise intervention added to weight loss treatment at 6 months is effective for weight loss and maintenance.

METHODS

A total of 120 obese subjects (body mass index > 30) were randomly assigned to intensified behavioral modification (iBM) (n = 30), behavioral modification + exercise from 0 to 3 months (circuit weight training group 1 [CWT1]) (n = 30), behavioral modification + exercise from 6 to 9 months (CWT2) (n = 30), and a control group (CON) (n = 30). Health behavior, weight, waist circumference, and 2-h glucose tolerance test with insulin measurements were measured at 0, 3, 9, and 24 months.

RESULTS

Eighty-five subjects (mean age = 46 yr, body mass index = 36.3, 75.3% women) completed the trial. A significant weight loss occurred in CWT1 (-8.5 kg, P > 0.001), iBM (-5.5 kg, P > 0.001), and CWT2 (-4.4 kg, P = 0.007). CWT1 showed the highest reduction in waist circumference at 9 months (mean difference = -11.5 cm, P < 0.001) and 24 months (mean difference = -8.8 cm, P < 0.001). Both fasting and 2-h insulin values improved in the intervention groups compared with CON. A significant decrease in 2-h insulin values from baseline was found in CWT1 and CWT2. Matsuda index improved in the CWT1 group from the baseline to 24 months (2.03, P = 0.025).

CONCLUSION

The most effective weight loss regimen is a combination of iBM and weight training introduced from the very beginning of the weight loss period. Treatment of morbid obesity should include an intensive start with exercise and diet regardless of weight status.

Physical activity levels and associated cardiovascular disease risk factors among postmenopausal rural women of Bangladesh

OBJECTIVES

The role of physical inactivity in relation to cardiovascular disease (CVD) among postmenopausal women is understudied. The main objective of this study was to measure the physical activity levels (PALs) and evaluate its relation to other CVD risk factors among postmenopausal rural women of Bangladesh.

METHODS

A cross-sectional study was conducted among 265 postmenopausal women aged 40-70 years who visited the outpatient department of a primary health-care center situated in the village Karamtola of Gazipur district. A pretested modified questionnaire of STEP-wise approach to Surveillance (STEPS) of noncommunicable disease risk factors was used to collect data on sociodemographic and lifestyle factors. PAL was determined by the Estimated Energy Requirement (EER) equation of the Dietary Reference Intakes (DRIs) Committee, and association with CVD risk factors was examined by Spearman's rank correlation.

RESULTS

More than half (58.1%) of the postmenopausal women were identified as sedentary with high prevalence of central obesity (73.2%) among them. CVD risk factors including age (r = -0.228, p < 0.01), age at menopause (r = -0.129, p < 0.05), duration of menopause (r = -0.183, p < 0.05), 2-h plasma glucose (r = -0.148, p < 0.05), total cholesterol (r = -0.138, p < 0.05), low-density lipoprotein cholesterol (r = -0.122, p < 0.05), and triglyceride (r = -0.168, p < 0.01) showed a significant as well as inverse association with Metabolic Equivalent of Task (MET) of physical activity.

CONCLUSION

Low PAL and significant inverse correlation with various CVD risk factors demand interventions to maintain higher PAL among postmenopausal women of Bangladesh.

Association between physical activity and abnormal glucose metabolism-A population-based cross-sectional study in China

BACKGROUND

Association between physical activity and abnormal glucose metabolism (AGM) remains unclear.

METHODS

Data were collected from a random sample of the Chinese population aged 26-77 years. Participants were classified into an AGM group or a normal glucose tolerance (NGT) group. Total physical activity energy expenditure (PAEE), sedentary time, and ratios of PAEE in different domains to the total PAEE were calculated according to the International Physical Activity Questionnaire. Logistic regression was used to analyze the associations between total PAEE, ratios of PAEE under different domains to total PAEE, sedentary time, and AGM.

RESULTS

Data from 3510 participants aged 50 ± 12 years were analyzed; 1390 (39.6%) were diagnosed with AGM. In the multivariate logistic regression analysis, total PAEE (1000 MET-min/week) was significantly associated with AGM [OR (95% CI) 0.96 (0.94, 0.99)]. After stratification by sex and BMI, total PAEE was negatively associated with AGM in men and overweight people. The ratios of PAEE in different domains to total PAEE or sedentary time were not associated with AGM.

CONCLUSIONS

Total PAEE was negatively associated with AGM. Ratios of PAEE in different domains to total PAEE and sedentary time were not associated with AGM in this Chinese population.

Glucose effectiveness, but not insulin sensitivity, is improved after short-term interval training in individuals with type 2 diabetes mellitus: a controlled, randomised, crossover trial

AIMS/HYPOTHESIS

The role of glucose effectiveness (S _G) in training-induced improvements in glucose metabolism in individuals with type 2 diabetes is unknown. The objectives and primary outcomes of this study were: (1) to assess the efficacy of interval walking training (IWT) and continuous walking training (CWT) on S _G and insulin sensitivity (S _I) in individuals with type 2 diabetes; and (2) to assess the association of changes in S _G and S _I with changes in glycaemic control.

METHODS

Fourteen participants with type 2 diabetes underwent three trials (IWT, CWT and no training) in a crossover study. Exclusion criteria were exogenous insulin treatment, smoking, pregnancy, contraindications to structured physical activity and participation in recurrent training (>90 min/week). The trials were performed in a randomised order (computerised-generated randomisation). IWT and CWT consisted of ten supervised treadmill walking sessions, each lasting 60 min, over 2 weeks. IWT was performed as repeated cycles of 3 min slow walking and 3 min fast walking (aiming for 54% and 89% of [Formula: see text], respectively, which was measured during the last minute of each interval), and CWT was performed aiming for a moderate walking speed (73% of [Formula: see text]). A two-step (pancreatic and hyperinsulinaemic) hyperglycaemic clamp was implemented before and after each trial. All data were collected in a hospitalised setting. Neither participants nor assessors were blinded to the trial interventions.

RESULTS

Thirteen individuals completed all procedures and were included in the analyses. IWT improved S _G (mean ± SEM: 0.6 ± 0.1 mg kg^-1 min^-1, p < 0.05) but not S _I (p > 0.05), whereas CWT matched for energy expenditure and time duration improved neither S _G nor S _I (both p > 0.05). Changes in S _G, but not in S _I, were associated with changes in mean (β = -0.62 ± 0.23, r ² = 0.17, p < 0.01) and maximum (β = -1.18 ± 0.52, r ² = 0.12, p < 0.05) glucose levels during 24 h continuous glucose monitoring.

CONCLUSIONS/INTERPRETATION

Two weeks of IWT, but not CWT, improves S _G but not S _I in individuals with type 2 diabetes. Moreover, changes in S _G are associated with changes in glycaemic control. Therefore, increased S _G is likely an important mechanism by which training improves glycaemic control in individuals with type 2 diabetes.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02320526 FUNDING: CFAS is supported by a grant from TrygFonden. During the study period, the Centre of Inflammation and Metabolism (CIM) was supported by a grant from the Danish National Research Foundation (DNRF55). The study was further supported by grants from Diabetesforeningen, Augustinusfonden and Krista og Viggo Petersens Fond. CIM/CFAS is a member of DD2-the Danish Center for Strategic Research in Type 2 Diabetes (the Danish Council for Strategic Research, grant no. 09-067009 and 09-075724).

Physical Activity and Improvement of Glycemia in Prediabetes by Different Diagnostic Criteria

Context

The effects of physical activity (PA) on improvement of glycemia may differ between prediabetic individuals defined by oral glucose tolerance test vs glycated hemoglobin (HbA1c).

Objective

We studied the association between PA and improvement of glycemia in individuals with prediabetes defined by glucose vs HbA1c criteria.

Design, Setting, and Participants

From the Whitehall II study, 957 participants with prediabetes defined by isolated impaired fasting glucose (i-IFG), isolated impaired glucose tolerance (i-IGT), or both and 457 with prediabetes defined by HbA1c were included.

Main Outcome Measures

The associations of PA with concomitant changes in glucose-related outcomes during 5 years of follow-up were analyzed. A recursive partitioning analysis was performed to study heterogeneity in the association between baseline PA and the probability of reversion to normoglycemia.

Results

After 5 years of follow-up, 405 (42%) individuals with glucose-defined prediabetes reverted to normal glucose tolerance (NGT). A 5-year increase in moderate-to-vigorous-intensity PA was associated with improvements in insulin sensitivity and β-cell function, but PA was not generally associated with reversion to NGT. Only among women ≥50 years with i-IFG or i-IGT, higher amounts of PA were associated with higher probability of reversion to NGT. In HbA1c-defined prediabetes, only 20 individuals (4.4%) reverted to normoglycemia, and PA was not associated with improvement in glycemic markers.

Conclusions

PA may be particularly important for reversion to normoglycemia among older women with i-IFG or i-IGT. Individuals with prediabetes identified by HbA1c have a low probability of reversion to normoglycemia, and their changes in glycemia are not related to PA.

Protocol for a randomised controlled trial of the effect of dapagliflozin, metformin and exercise on glycaemic variability, body composition and cardiovascular risk in prediabetes (the PRE-D Trial)

INTRODUCTION

The primary aim of this study is to compare the efficacy of three short-term glucose-lowering interventions (exercise, metformin and dapagliflozin) on glycaemic variability in overweight or obese men and women with elevated diabetes risk (ie, prediabetes, defined as haemoglobin A1c (HbA1c)39-47 mmol/mol / 5.7%-6.4%). The secondary aims are to investigate the effects of the interventions on body composition and cardiometabolic risk factors.

METHODS AND ANALYSIS

The Pre-D Trial is an investigator-initiated, randomised, controlled, parallel, open-label, superiority trial. The study aims to assign 120 participants in a 1:1:1:1 ratio to receive one of four interventions for 13 weeks: (1) dapagliflozin (10 mg once daily); (2) metformin (850 mg twice daily); (3) exercise (interval training, 5 days a week, 30 min per session); or (4) control (lifestyle advice). After the 13 weeks of intervention, a follow-up period of 13 weeks will follow to study the long-term effects of the interventions. The primary endpoint is reduction from baseline to end-of treatment (13 weeks) in mean amplitude of glycaemic excursions measured by continuous glucose monitoring. The secondary endpoints include concomitant changes in various measures of glucose metabolism, body weight, cardiorespiratory fitness, blood pressure, plasma lipids, objectively measured physical activity and dietary intake.

ETHICS AND DISSEMINATION

The study protocol has been approved by the Ethics Committee of the Capital Region and the Danish Medicines Agency. Approval of data and biobank storage has been obtained from the Danish Data Protection Board. The study will be carried out according to the Declaration of Helsinki and to the regulations for good clinical practice. The results from this trial will allow a number of research questions concerning the effect of exercise versus dapagliflozin or metformin in HbA1c-defined prediabetes to be addressed.

TRIAL REGISTRATION

NCT02695810.

Sociocultural Characteristic, Lifestyle, and Metabolic Risk Factors Among a Sample of Kuwaiti Male University Students

In the past six decades, the Kuwaiti population has been exposed to rapid transformation in the quality of diet intake, daily activities, and career types. This major socioeconomic shift was accompanied by the introduction of both communicable and noncommunicable chronic diseases afflicting people of all ages. This article aims to detect a relationship between sociocultural characteristics—such as physical activity, dietary habits, and smoking—and the prevalence of metabolic syndrome (MetS). A descriptive, cross-sectional survey was conducted among 262 male university students in Kuwait; participants were selected by using a convenient nonrandom opportunistic sample. Associated social and health factors were obtained using a closed-ended questionnaire. BMI and blood tests that include clusters of MetS risk components were drawn from participants in primary health care clinics. More than half of the participants were overweight and obese; 74.4% of the participants reported they did not visit a nutritionist; 69.8% said that they are currently not on a diet; 53.4% of the students were nonsmokers; 42.7% reported moderate to very low daily physical activity. The prevalence of MetS components increased among students with older age, employed, and married (p < .001), higher BMI, higher income, smoking, fewer number of family members living, and belonging to the Shia religious sect (p < .05). The high frequency of MetS among younger students needs to be considered by Kuwaiti community members and the government to highlight the risk factors of MetS on individuals’ well-being, quality of life, and life expectation.

Targeting specific interstitial glycemic parameters with high-intensity interval exercise and fasted-state exercise in type 2 diabetes

AIMS

To compare the acute glycemic responses to a bout of high-intensity interval exercise (HIIE) and energy-matched moderate-intensity continuous exercise (MICE) performed under fasted and postprandial conditions.

METHODS

A randomized, controlled, crossover design was used. Ten individuals with type 2 diabetes were each tested in five experimental conditions after an overnight fast: 1) fasted-state HIIE (HIIEfast); 2) post-breakfast HIIE (HIIEfed); 3) fasted-state MICE (MICEfast); 4) post-breakfast MICE (MICEfed); and 5) no exercise (control). MICE was performed at workload corresponding to 55% of V.V̇O2peak, whereas HIIE was composed of repetitions of three minutes at workload corresponding to 40% followed by one minute at workload corresponding to 100% V.V̇̇O2peak. Interstitial glucose was monitored by continuous glucose monitoring over 24h under standardized diet and medication.

RESULTS

Fasted-state exercise attenuated postprandial glycemic increments (p<0.05) to a greater extent than post-breakfast exercise did. HIIE reduced nocturnal and fasting glycemia on the day following exercise more than MICE did (main effect: both p<0.05). Compared to the control condition, HIIEfast lowered most interstitial glycemic parameters, i.e., 24-h mean glucose (-1.5mmol·l(-1); p<0.05), fasting glucose (-1.0mmol·l(-1); p<0.05), overall postprandial glycemic increment (-257mmol·360min·l(-1); p<0.05), glycemic variability (-1.79mmol·l(-1); p<0.05), and time spent in hyperglycemia (-283min; p<0.05).

CONCLUSION

This study showed that HIIE is more effective than MICE in lowering nocturnal/fasting glycemia. Exercise performed in the fasted state reduces postprandial glycemic increments to a greater extent than post-breakfast exercise does. Performing HIIE under fasted condition may be most advantageous as it lowered most aspects of glycemia.

Physical Activity and Sedentary Behavior Associated with Components of Metabolic Syndrome among People in Rural China

Background

Metabolic syndrome is prevalent worldwide and its prevalence is related to physical activity, race, and lifestyle. Little data is available for people living in rural areas of China. In this study we examined associations of physical activity and sedentary behaviors with metabolic syndrome components among people in rural China.

Methods

The Nantong Metabolic Syndrome Study recruited 13,505 female and 6,997 male participants between 2007 and 2008. Data of socio-demographic characteristics and lifestyle were collected. The associations of physical activity and sedentary behaviors with metabolic syndrome components were analyzed.

Results

Prevalence of metabolic syndrome was 21.6%. It was significantly lower in men than in women. Low risks of metabolic syndrome were observed in those who did less sitting and engaged in more vigorous physical activity. The highest tertile of vigorous physical activity was associated with 15–40% decreased odds of metabolic syndrome and all of its components, except for low high-density lipoprotein cholesterol in men. Women with the highest tertile of moderate physical activity had 15–30% lower odds of central obesity, high glucose, and high triglycerides compared with those in the lowest tertile. Sitting time >42 hours per week had a 4%-12% attributable risk of metabolic syndrome, central obesity, and high triglycerides in both genders, and abnormal glucose and diastolic blood pressure in women. Sleeping for more than 8 hours per day was associated with risk of high serum glucose and lipids.

Conclusions

Our data suggested that physical activity has a preventive effect against metabolic syndrome and all its abnormal components, and that longer sitting time and sleep duration are associated with an increased risk of metabolic syndrome components, including central obesity and high triglycerides, glucose, and diastolic blood pressure. This study could provide information for future investigation into these associations. Also, recommendations are developed to reduce prevalence of metabolic syndrome and its components in rural Chinese populations.

Abdominal obesity as a mediator of the influence of physical activity on insulin resistance in Spanish adults

OBJECTIVE

The aim of the study was to analyze the relationship between moderate-to-vigorous physical activity (MVPA) and insulin resistance (IR) in Spanish adults and to examine whether this relationship is mediated by abdominal obesity (waist circumference - WC).

METHODS

The cross-sectional study included 1162 healthy subjects belonging to the EVIDENT study (mean age 55.0±13.3years; 61.8% women) from six different Spanish provinces. Moderate-to-vigorous physical activity (MVPA) was measured objectively over 7days using Actigraph accelerometers, collecting data in 60-second epochs, and retaining respondents with ≥4 valid days for the analysis. The homeostasis model of assessment (HOMA-IR) was used to determine IR, and its individual components - fasting glucose and insulin - were determined using standard protocols. Linear regression models were fitted according to Baron and Kenny's procedures for mediation analysis.

RESULTS

Fasting insulin and HOMA-IR levels were significantly worse in adults who spent fewer minutes in MVPA (first quartile≤30.1 and 22.7min/day in men and women, respectively) after adjusting for age, sex, smoking habits, drinking habits, accelerometer wear time, sedentary time, and Mediterranean diet adherence. However, when WC was added to the ANCOVA models as a covariate, the effects disappeared. Mediation analysis reported that WC acts as a full mediator in the relationship between MVPA and IR (HOMA-IR and fasting insulin).

CONCLUSION

These findings show that WC plays a pivotal role in the relationship between MVPA and IR, and therefore highlights that decreasing abdominal obesity might be considered as an intermediate outcome for evaluating interventions aimed at preventing diabetes mellitus.

Physical activity energy expenditure vs cardiorespiratory fitness level in impaired glucose metabolism

AIM/HYPOTHESIS

Little is known about the relative roles of physical activity energy expenditure (PAEE) and cardiorespiratory fitness (CRF) as determinants of glucose regulation. The aim of this study was to examine the associations of PAEE and CRF with markers of glucose metabolism, and to test the hypothesis that CRF modifies the association between PAEE and glucose metabolism.

METHODS

We analysed cross-sectional data from 755 adults from the Danish ADDITION-PRO study. On the basis of OGTT results, participants without known diabetes were classified as having normal glucose tolerance, isolated impaired fasting glycaemia (i-IFG), isolated impaired glucose tolerance (i-IGT), combined IFG + IGT or screen-detected diabetes mellitus. Markers of insulin sensitivity and beta cell function were determined. PAEE was measured using a combined heart rate and movement sensor. CRF (maximal oxygen uptake) was estimated using a submaximal 8 min step test. The associations were examined by linear regression analysis. Results were adjusted for relevant confounders.

RESULTS

PAEE and CRF were reduced in individuals with i-IGT, combined IFG + IGT and screen-detected diabetes mellitus, but were not significantly different in individuals with i-IFG compared with those with normal glucose tolerance. When adjusting CRF for PAEE and vice versa, PAEE and CRF were both associated with lower fasting and 2 h insulin and higher peripheral insulin sensitivity. CRF was additionally associated with lower fasting and 2 h glucose and higher insulin sensitivity and beta cell function. There was no interaction between CRF and PAEE for any markers of glucose metabolism.

CONCLUSIONS/INTERPRETATION

Only CRF, not PAEE, appears to be independently associated with plasma glucose levels and beta cell function, suggesting that CRF may be particularly important for glycaemic control.

Cardiorespiratory Fitness and Light-Intensity Physical Activity Are Independently Associated with Reduced Cardiovascular Disease Risk in Urban Black South African Women: A Cross-Sectional Study

BACKGROUND

Low levels of physical activity, poor cardiorespiratory fitness, and a sedentary lifestyle have been associated with increased risk for cardiovascular disease (CVD) and type 2 diabetes (T2D). Few studies have examined their independent associations in an urban black sub-Saharan African population.

OBJECTIVES

To examine the independent associations of physical activity, cardiorespiratory fitness, and sedentary time on body composition and cardiometabolic risk factors for CVD and T2D in black South African women.

MATERIALS AND METHODS

A subsample (n = 76; 18-45 years) was recruited, as part of a cross-sectional study. Accelerometry, cardiorespiratory fitness, body composition, insulin sensitivity, serum lipids, and blood pressure were measured.

RESULTS

Light- but not moderate- to vigorous intensity physical activity was inversely associated with trunk fat mass (r = -0.25, P = 0.03). Sedentary time was associated with triglyceride (TG) (r = 0.36, P = 0.01) and TG/HDL-C (r = 0.34, P = 0.04), and these relationships were independent of body fat. Cardiorespiratory fitness was inversely associated with body fat % (r = -0.34, P = 0.02), central fat mass (r = -0.31, P = 0.03), visceral adipose tissue (VAT, r = -0.47, P < 0.01), and insulin resistance (HOMA-IR; r = -0.41, P = 0.01). The association between cardiorespiratory fitness and HOMA-IR was independent of body fat and physical activity, but not VAT. Cardiorespiratory fitness was inversely associated with sedentary time (r = -0.31, P = 0.03), but not with any of the physical activity variables (P > 0.05).

CONCLUSION

Both physical activity and cardiorespiratory fitness were associated with reduced total and central fat mass, VAT, and reduced cardiometabolic risk for CVD and T2D. Longitudinal studies are required to confirm whether the promotion of increasing light physical activity, while reducing sedentary time and increasing cardiorespiratory fitness, reduces the risk for obesity, CVD and T2D.

The diagnosis of posttransplantation diabetes mellitus: meeting the challenges

Posttransplantation diabetes mellitus (PTDM) is a major complication after renal transplantation due to its negative impact on patient and graft survival, and affects up to 40% of renal transplant recipients. The generation of evidence regarding its optimal treatment is now progressing with some emphasis on early postoperative insulin treatment that targets β-cell failure. This therapy seems to benefit renal transplant patients but contrasts with previous PTDM guidelines that were following treatment of type 2 diabetes mellitus (DM): oral antidiabetics first, insulin last. Similarly, in the current PTDM consensus recommendations, diagnostic procedures are in accordance with the American Diabetes Association (ADA) recommendations for diagnosis of DM. PTDM and type 2 DM, however, are distinct disease entities with different pathophysiological backgrounds. This review will discuss the significance of the standard diagnostic criteria for DM in patients after renal transplantation without prior DM. In particular, the role of glycated hemoglobin (HbA1c) and oral glucose tolerance testing (OGTT) will be reviewed. In addition, the potential role of other glycated proteins and continuous glucose monitoring will be covered, although these parameters are not yet part of the consensus recommendations.

Daily Physical Activity Assessed by a Triaxial Accelerometer Is Beneficially Associated with Waist Circumference, Serum Triglycerides, and Insulin Resistance in Japanese Patients with Prediabetes or Untreated Early Type 2 Diabetes

AIM

To investigate the association between daily physical activity and metabolic risk factors in Japanese adults with prediabetes or untreated early type 2 diabetes (T2D).

METHODS

Daily physical activity level was measured using a triaxial accelerometer. We assessed correlations between physical activity level and waist circumference, blood pressure, fasting levels of plasma glucose, serum triglycerides, and insulin and homeostasis model assessment-insulin resistance (HOMA-IR).

RESULTS

A total of 80 patients were studied. After adjustment for age and body mass index, in all subjects, physical activity level was negatively associated with waist circumference (β = -0.124, P = 0.018) and fasting serum triglycerides (β = -0.239, P = 0.035), insulin (β = -0.224, P = 0.022). In men, physical activity level was negatively associated with systolic blood pressure (β = -0.351, P = 0.044), fasting plasma glucose (β = -0.369, P = 0.025) and insulin (β = -0.362, P = 0.012), and HOMA-IR (β = -0.371, P = 0.011). No significant associations were found between physical activity level and metabolic risk factors in women.

CONCLUSION

Objectively measured daily physical activity is beneficially associated with waist circumference, serum triglycerides, and insulin resistance in individuals with prediabetes or untreated early T2D. (This trial is registered with UMIN000015774.).

Insulin resistance and beta-cell function in different ethnic groups in Kenya: the role of abdominal fat distribution

Little is known about the pathophysiology of diabetes in Africans. Thus, we assessed whether insulin resistance and beta-cell function differed by ethnicity in Kenya and whether differences were modified by abdominal fat distribution. A cross-sectional study in 1,087 rural Luo (n = 361), Kamba (n = 378), and Maasai (n = 348) was conducted. All participants had a standard 75-g oral glucose tolerance test (OGTT). Venous blood samples were collected at 0, 30, and 120 min. Serum insulin was analysed at 0 and 30 min. From the OGTT, we assessed the homoeostasis model assessment of insulin resistance by computer model, early phase insulin secretion, and disposition index (DI) dividing insulin secretion by insulin resistance. Abdominal subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) thickness were carried out by ultrasonography. Linear regression analyses were done to assess ethnic differences in insulin indices. The Maasai had 32 and 17% higher insulin resistance than the Luo and Kamba, respectively (p < 0.001). Early phase insulin secretion was 16% higher in the Maasai compared to the Luo (p < 0.001). DI was 12% (p = 0.002) and 10% (p = 0.015) lower in the Maasai compared to the Luo and Kamba, respectively. Adjustments of SAT (range 0.1-7.1 cm) and VAT (range 1.5-14.2 cm) largely explained these inter-group differences with the Maasai having the highest combined abdominal fat accumulation. The Maasai had the highest insulin resistance and secretion, but the lowest relative beta-cell function compared to the Luo and Kamba. These differences were primarily explained by abdominal fat distribution.

Sedentary behavior and mortality in older women: the Women's Health Initiative

BACKGROUND

Although epidemiologic studies have shown associations between sedentary behavior and mortality, few have focused on older women with adequate minority representation and few have controlled for both physical activity and functional status.

PURPOSE

The objective of this study was to determine the relationship between sedentary time and total; cardiovascular disease (CVD); coronary heart disease (CHD); and cancer mortality in a prospective, multiethnic cohort of postmenopausal women.

METHODS

The study population included 92,234 women aged 50-79 years at baseline (1993-1998) who participated in the Women's Health Initiative Observational Study through September 2010. Self-reported sedentary time was assessed by questionnaire and examined in 4 categories (≤4, >4-8, ≥8-11, >11 hours). Mortality risks were examined using Cox proportional hazard models adjusting for confounders. Models were also stratified by age, race/ethnicity, body mass index, physical activity, physical function, and chronic disease to examine possible effect modification. Analyses were conducted in 2012-2013.

RESULTS

The mean follow-up period was 12 years. Compared with women who reported the least sedentary time, women reporting the highest sedentary time had increased risk of all-cause mortality in the multivariate model (HR=1.12, 95% CI=1.05, 1.21). Results comparing the highest versus lowest categories for CVD, CHD, and cancer mortality were as follows: HR=1.13, 95% CI=0.99, 1.29; HR=1.27, 95% CI=1.04, 1.55; and HR=1.21, 95% CI=1.07, 1.37, respectively. For all mortality outcomes, there were significant linear tests for trend.

CONCLUSIONS

There was a linear relationship between greater amounts of sedentary time and mortality risk after controlling for multiple potential confounders.

Insulin sensitivity and metabolic flexibility following exercise training among different obese insulin-resistant phenotypes

Impaired fasting glucose (IFG) blunts the reversal of impaired glucose tolerance (IGT) after exercise training. Metabolic inflexibility has been implicated in the etiology of insulin resistance; however, the efficacy of exercise on peripheral and hepatic insulin sensitivity or substrate utilization in adults with IFG, IGT, or IFG + IGT is unknown. Twenty-four older (66.7 ± 0.8 yr) obese (34.2 ± 0.9 kg/m(2)) adults were categorized as IFG (n = 8), IGT (n = 8), or IFG + IGT (n = 8) according to a 75-g oral glucose tolerance test (OGTT). Subjects underwent 12-wk of exercise (60 min/day for 5 days/wk at ∼85% HRmax) and were instructed to maintain a eucaloric diet. A euglycemic hyperinsulinemic clamp (40 mU·m(2)·min(-1)) with [6,6-(2)H]glucose was used to determine peripheral and hepatic insulin sensitivity. Nonoxidative glucose disposal and metabolic flexibility [insulin-stimulated respiratory quotient (RQ) minus fasting RQ] were also assessed. Glucose incremental area under the curve (iAUCOGTT) was calculated from the OGTT. Exercise increased clamp-derived peripheral and hepatic insulin sensitivity more in adults with IFG or IGT alone than with IFG + IGT (P < 0.05). Exercise reduced glucose iAUCOGTT in IGT only (P < 0.05), and the decrease in glucose iAUCOGTT was inversely correlated with the increase in peripheral but not hepatic insulin sensitivity (P < 0.01). Increased clamp-derived peripheral insulin sensitivity was also correlated with enhanced metabolic flexibility, reduced fasting RQ, and higher nonoxidative glucose disposal (P < 0.05). Adults with IFG + IGT had smaller gains in clamp-derived peripheral insulin sensitivity and metabolic flexibility, which was related to blunted improvements in postprandial glucose. Additional work is required to assess the molecular mechanism(s) by which chronic hyperglycemia modifies insulin sensitivity following exercise training.

The effects of free-living interval-walking training on glycemic control, body composition, and physical fitness in type 2 diabetic patients: a randomized, controlled trial

OBJECTIVE

To evaluate the feasibility of free-living walking training in type 2 diabetic patients and to investigate the effects of interval-walking training versus continuous-walking training upon physical fitness, body composition, and glycemic control.

RESEARCH DESIGN AND METHODS

Subjects with type 2 diabetes were randomized to a control (n = 8), continuous-walking (n = 12), or interval-walking group (n = 12). Training groups were prescribed five sessions per week (60 min/session) and were controlled with an accelerometer and a heart-rate monitor. Continuous walkers performed all training at moderate intensity, whereas interval walkers alternated 3-min repetitions at low and high intensity. Before and after the 4-month intervention, the following variables were measured: VO(2)max, body composition, and glycemic control (fasting glucose, HbA(1c), oral glucose tolerance test, and continuous glucose monitoring [CGM]).

RESULTS

Training adherence was high (89 ± 4%), and training energy expenditure and mean intensity were comparable. VO(2)max increased 16.1 ± 3.7% in the interval-walking group (P < 0.05), whereas no changes were observed in the continuous-walking or control group. Body mass and adiposity (fat mass and visceral fat) decreased in the interval-walking group only (P < 0.05). Glycemic control (elevated mean CGM glucose levels and increased fasting insulin) worsened in the control group (P < 0.05), whereas mean (P = 0.05) and maximum (P < 0.05) CGM glucose levels decreased in the interval-walking group. The continuous walkers showed no changes in glycemic control.

CONCLUSIONS

Free-living walking training is feasible in type 2 diabetic patients. Continuous walking offsets the deterioration in glycemia seen in the control group, and interval walking is superior to energy expenditure-matched continuous walking for improving physical fitness, body composition, and glycemic control.

Sedentary Behavior and Physical Function Decline in Older Women: Findings from the Women's Health Initiative

Sedentary behavior is associated with deleterious health outcomes. This study evaluated the association between sedentary time and physical function among postmenopausal women in the Women's Health Initiative Observational Study. Data for this prospective cohort study were collected between 1993-1998 (enrollment) and 2009, with an average of 12.3 follow-up years. Analyses included 61,609 women (aged 50-79 years at baseline). Sedentary time was estimated by questionnaire; physical function was measured using the RAND SF-36 physical function scale. Mixed-model analysis of repeated measures was used to estimate the relationship of sedentary time exposures and changes in physical function adjusting for relevant covariates. Compared to women reporting sedentary time of ≤6 hours/day, those with greater amounts of sedentary time (>6-8 hours/day, >8-11 hours/day, >11 hours/day) reported lower physical function between baseline and follow up (coefficient = -0.78, CI = -0.98, -0.57, -1.48, CI = -1.71, -1.25, -3.13, and CI = -3.36, -2.89, respectively P < 0.001). Sedentary time was strongly associated with diminished physical function and most pronounced among older women and those reporting the greatest sedentary time. Maintaining physical function with age may be improved by pairing messages to limit sedentary activities with those promoting recommended levels of physical activity.

No interactions between previously associated 2-hour glucose gene variants and physical activity or BMI on 2-hour glucose levels

Gene-lifestyle interactions have been suggested to contribute to the development of type 2 diabetes. Glucose levels 2 h after a standard 75-g glucose challenge are used to diagnose diabetes and are associated with both genetic and lifestyle factors. However, whether these factors interact to determine 2-h glucose levels is unknown. We meta-analyzed single nucleotide polymorphism (SNP) × BMI and SNP × physical activity (PA) interaction regression models for five SNPs previously associated with 2-h glucose levels from up to 22 studies comprising 54,884 individuals without diabetes. PA levels were dichotomized, with individuals below the first quintile classified as inactive (20%) and the remainder as active (80%). BMI was considered a continuous trait. Inactive individuals had higher 2-h glucose levels than active individuals (β = 0.22 mmol/L [95% CI 0.13-0.31], P = 1.63 × 10(-6)). All SNPs were associated with 2-h glucose (β = 0.06-0.12 mmol/allele, P ≤ 1.53 × 10(-7)), but no significant interactions were found with PA (P > 0.18) or BMI (P ≥ 0.04). In this large study of gene-lifestyle interaction, we observed no interactions between genetic and lifestyle factors, both of which were associated with 2-h glucose. It is perhaps unlikely that top loci from genome-wide association studies will exhibit strong subgroup-specific effects, and may not, therefore, make the best candidates for the study of interactions.

Accelerometer-determined moderate intensity lifestyle activity and cardiometabolic health

OBJECTIVE

Objective To assess the relationship between moderate intensity lifestyle activity (LA) and cardiometabolic health using accelerometer data from the National Health and Nutrition Examination Survey (NHANES) 2005-2006.

METHODS

One thousand three hundred and seventy-one adults (50% men; 71% non-Hispanic white) provided valid data to quantify time in LA [760-2019 counts per minute (CPM)] and moderate-to-vigorous physical activity (MVPA; ≥ 2020 CPM). Associations between LA [minutes per day (min/day); steps per day (steps/day)], and cardiometabolic risk factors [triglycerides, HDL-cholesterol (HDL-C), blood pressure, glucose, waist circumference], metabolic syndrome, self-reported hypertension and diabetes were investigated using logistic regression. Analyses were adjusted for age, gender, race/ethnicity, and MVPA categories.

RESULTS

Greater time in LA (min/day), independent from MVPA, was associated with lower odds of elevated triglycerides (OR, 95% CI per 30 LA minutes: (0.88, 0.80-0.98), low HDL-C (0.88, 0.83-0.94), elevated waist circumference (0.89, 0.84-0.95), metabolic syndrome (0.88, 0.80-0.97), and diabetes (0.65, 0.51-0.83) [corrected]. The same cardiometabolic risk factors were also significantly associated with LA steps/day. No significant association was found between LA (min/day or steps/day) and glucose or blood pressure.

CONCLUSION

Accumulation of time or steps in LA is independently related to lower odds for certain cardiometabolic risk factors. Research should consider the effects of increasing LA, which could influence future physical activity recommendations.

Physical inactivity and chronic kidney disease in Australian adults: the AusDiab study

BACKGROUND AND AIMS

Physical inactivity is associated with cardiovascular risk however its relationship to chronic kidney disease is largely unknown. We examined the association between leisure-time physical activity and risk of chronic kidney disease in a prospective, population-based cohort of Australians aged ≥ 25 years (AusDiab).

METHODS AND RESULTS

The baseline sample included 10,966 adults (4951 males and 6015 females). From this sample, 6318 participants with complete baseline and 5-year follow-up urinalysis and serum creatinine measurements formed the study population for longitudinal analysis. Self-reported leisure-time physical activity was measured using a validated, interviewer-administered questionnaire. Compared with sufficiently active individuals (≥ 150 min physical activity per week), those who were inactive (0 min/week) were more likely to have albuminuria at baseline (multivariate-adjusted OR=1.34, 95% CI 1.10-1.63). Inactivity (versus sufficient physical activity) was associated with increased age- and sex-adjusted odds of an estimated glomerular filtration rate <3rd percentile (OR=1.30, 95% CI 1.02-1.65), although this was not significant after multivariate adjustment (OR=1.17, 95% CI 0.91-1.50). Obese, inactive individuals were significantly more likely to have albuminuria at baseline (multivariate-adjusted OR=1.74, 95% CI 1.35-2.25), compared with sufficiently active, non-obese individuals. Baseline physical activity status was not significantly associated with longitudinal outcomes.

CONCLUSIONS

Physical inactivity is cross-sectionally associated with albuminuria prevalence, particularly when combined with obesity. Future studies are needed to determine whether this association is causal and the importance of physical activity in CKD prevention.

High cardiorespiratory fitness is more beneficial in pre-diabetic men than women

OBJECTIVES

To investigate gender-specific relationships between cardiorespiratory fitness and factors that predict the development of diabetes and to identify the risk factors that predict fasting plasma glucose and 2-hour plasma glucose levels.

INTRODUCTION

Different risk factors (e.g., low cardiorespiratory fitness) may cause elevated plasma glucose levels in men compared to women. Therefore, gender-specific analyses are needed.

METHODS

Cardiorespiratory fitness (maximal power output achieved during a standard cycle ergometry test), resting blood pressure, total serum cholesterol, high-density lipoprotein cholesterol and triglyceride levels were measured in 32 pre-diabetic men (mean age: 57.2 ± 6.8 years; mean body mass index (BMI): 28.5 ± 3.0 kg/m²) and 40 pre-diabetic women (mean age: 55.0 ± 7.3 years, mean BMI: 30.4 ± 5.7 kg/m²). A stepwise regression with backward variable selection was performed to construct models that predict 2-hour and fasting plasma glucose levels.

RESULTS

Maximal power output was inversely related to the 2-hour plasma glucose level in the entire group (r= -0.237, p<0.05), but this relationship was significant only for males (r= -0.404, p<0.05). No significant correlation was found between female gender and cardiorespiratory fitness. Age and cardiorespiratory fitness were significant predictors of 2-hour plasma glucose levels in men. High-density lipoprotein cholesterol was predictive of 2-hour plasma glucose levels in women. Triglycerides in women and BMI in men were the only predictors of fasting plasma glucose levels.

CONCLUSIONS

These findings may have consequences for the development of gender-specific diabetes prevention programs. Whereas increasing cardiorespiratory fitness should be a key goal for men, improving the lipid profile seems to be more beneficial for women. However, the present results do not negate the positive effects of increasing cardiorespiratory fitness in women.

Objective light-intensity physical activity associations with rated health in older adults

The extent to which light-intensity physical activity contributes to health in older adults is not well known. The authors examined associations between physical activity across the intensity spectrum (sedentary to vigorous) and health and well-being variables in older adults. Two 7-day assessments of accelerometry from 2005 to 2007 were collected 6 months apart in the observational Senior Neighborhood Quality of Life Study of adults aged >65 years in Baltimore, Maryland, and Seattle, Washington. Self-reported health and psychosocial variables (e.g., lower-extremity function, body weight, rated stress) were also collected. Physical activity based on existing accelerometer thresholds for moderate/vigorous, high-light, low-light, and sedentary categories were examined as correlates of physical health and psychosocial well-being in mixed-effects regression models. Participants (N = 862) were 75.4 (standard deviation, 6.8) years of age, 56% female, 71% white, and 58% overweight/obese. After adjustment for study covariates and time spent in moderate/vigorous physical activity and sedentary behavior, low-light and high-light physical activity were positively related to physical health (all P < 0.0001) and well-being (all P < 0.001). Additionally, replacing 30 minutes/day of sedentary time with equal amounts of low-light or high-light physical activity was associated with better physical health (all P < 0.0001). Objectively measured light-intensity physical activity is associated with physical health and well-being variables in older adults.

Association between physical activity and retinal microvascular signs: the Atherosclerosis Risk in Communities (ARIC) Study

OBJECTIVE

To examine the association between physical activity measured during leisure, sport, and work and retinal microvascular signs.

METHODS

Participants of the Atherosclerosis Risk in Communities (ARIC) Study, a population-based cross-sectional study, had retinal photographs taken at their third follow up visit (1993-1995). Retinal microvascular signs were assessed using a standardized protocol and retinal vascular caliber by a computer-assisted method. Leisure, sport, and work-related physical activity levels were determined through a modified Baecke physical activity questionnaire.

RESULTS

A higher level of physical activity during sport and work was significantly associated with a lower prevalence of arteriovenous (AV) nicking, wider venular caliber, and retinopathy. In multivariate models, persons with a level of sport-related physical activity above the median were less likely to have AV nicking (odds ratio [OR] = 0.87; 95% confidence interval [CI] 0.78-0.97) and wider retinal venules (OR = 0.91; 95% CI: 0.83-0.99). Persons with a level of work-related physical activity above the median were less likely to have diabetic retinopathy (OR = 0.66, 95% CI: 0.51-0.85).

CONCLUSIONS

In this cross-sectional analyzes, higher levels of physical activity was associated with a lower prevalence of retinal microvascular abnormalities.

Socioeconomic position, gender, health behaviours and biomarkers of cardiovascular disease and diabetes

Socio-economic gradients in cardiovascular disease (CVD) and diabetes have been found throughout the developed world and there is some evidence to suggest that these gradients may be steeper for women. Research on social gradients in biological risk factors for CVD and diabetes has received less attention and we do not know the extent to which gradients in biomarkers vary for men and women. We examined the associations between two indicators of socio-economic position (education and household income) and biomarkers of diabetes and cardiovascular disease (CVD) for men and women in a national, population-based study of 11,247 Australian adults. Multi-level linear regression was used to assess associations between education and income and glucose tolerance, dyslipidaemia, blood pressure (BP) and waist circumference before and after adjustment for behaviours (diet, smoking, physical activity, TV viewing time, and alcohol use). Measures of glucose tolerance included fasting plasma glucose and insulin and the results of a glucose tolerance test (2 h glucose) with higher levels of each indicating poorer glucose tolerance. Triglycerides and High Density Lipoprotein (HDL) Cholesterol were used as measures of dyslipidaemia with higher levels of the former and lower levels of the later being associated with CVD risk. Lower education and low income were associated with higher levels of fasting insulin, triglycerides and waist circumference in women. Women with low education had higher systolic and diastolic BP and low income women had higher 2 h glucose and lower HDL cholesterol. With only one exception (low income and systolic BP), all of these estimates were reduced by more than 20% when behavioural risk factors were included. Men with lower education had higher fasting plasma glucose, 2 h glucose, waist circumference and systolic BP and, with the exception of waist circumference, all of these estimates were reduced when health behaviours were included in the models. While low income was associated with higher levels of 2-h glucose and triglycerides it was also associated with better biomarker profiles including lower insulin, waist circumference and diastolic BP. We conclude that low socio-economic position is more consistently associated with a worse profile of biomarkers for CVD and diabetes for women.

Contribution of skeletal muscle mass on sex differences in 2-hour plasma glucose levels after oral glucose load in Thai subjects with normal glucose tolerance

Women have higher 2-hour plasma glucose levels after oral glucose challenge than men. The smaller skeletal muscle mass in women may contribute to the higher postload glucose levels. The objective of this study was to test the hypothesis that the different amount of skeletal muscle mass between men and women contributed to sex difference in postload plasma glucose levels in subjects with normal glucose tolerance. Forty-seven Thai subjects with normal glucose tolerance, 23 women and 24 age- and body mass index-matched men, were studied. Body fat, abdominal fat, and appendages lean mass were measured by dual-energy x-ray absorptiometry. Skeletal muscle insulin sensitivity was determined by euglycemic-hyperinsulinemic clamp. First-phase insulin secretion and hepatic insulin sensitivity were determined from oral glucose tolerance data. beta-Cell function was estimated from the homeostasis model assessment of %B by the homeostasis model assessment 2 model. Correlation and linear regression analysis were performed to identify factors contributing to variances of postload 2-hour plasma glucose levels. This study showed that women had significantly higher 2-hour plasma glucose levels and smaller skeletal muscle mass than men. Measures of insulin secretion and insulin sensitivity were not different between men and women. Male sex (r = -0.360, P = .013) and appendages lean mass (r = -0.411, P = .004) were negatively correlated with 2-hour plasma glucose, whereas log 2-hour insulin (r = 0.571, P < .0001), total body fat (r = 0.348, P = .016), and log abdominal fat (r = 0.298, P = .042) were positively correlated with 2-hour plasma glucose. The correlation of 2-hour plasma glucose and sex disappeared after adjustment for appendages lean mass. By multivariate linear regression analysis, log 2-hour insulin (beta = 18.9, P < .0001), log 30-minute insulin (beta = -36.3, P = .001), appendages lean mass (beta = -1.0 x 10(-3), P = .018), and hepatic insulin sensitivity index (beta = -17.3, P = .041) explained 54.2% of the variance of 2-hour plasma glucose. In conclusion, the higher postload 2-hour plasma glucose levels in women was not sex specific but was in part a result of the smaller skeletal muscle mass. The early insulin secretion, hepatic insulin sensitivity, and skeletal muscle mass were the significant factors negatively predicting 2-hour postload plasma glucose levels in Thai subjects with normal glucose tolerance.

Differential relationship between physical activity and progression to diabetes by glucose tolerance status: the Inter99 Study

AIMS/HYPOTHESIS

The aim of the study was to analyse how strongly commuting and leisure-time physical activity affect progression to diabetes and to study whether this relationship is different in individuals with isolated impaired fasting glucose (i-IFG) and isolated impaired glucose tolerance (i-IGT).

METHODS

We studied the incidence of diabetes in 4,031 individuals without diabetes at baseline who participated in the baseline and 5 year follow-up examinations of a population-based primary prevention study, the Inter99 Study. Glucose tolerance status at baseline and at follow-up were based on OGTTs. Commuting and leisure-time physical activity at baseline were assessed by questionnaire. We present rate ratios from Poisson regression analyses adjusted for relevant confounders.

RESULTS

The progression rate to diabetes was lower among physically active individuals in the total study population and particularly among those with i-IGT. The associations were attenuated and lost statistical significance after further adjustment for BMI. We observed no impact of physical activity on the progression to diabetes in individuals with i-IFG.

CONCLUSIONS/INTERPRETATION

Physical activity was associated with a lower progression to diabetes in the total study population and in individuals with i-IGT, a condition primarily characterised by muscle insulin resistance. Physical activity did not predict progression to diabetes in individuals with i-IFG, a condition primarily characterised by hepatic insulin resistance. Our results suggest that there is a differential relationship between physical activity and progression to diabetes among those with i-IFG and i-IGT. Therefore, clinical trials testing the effect of physical activity on progression from i-IFG to diabetes are needed.

TRIAL REGISTRATION

ClinicalTrials.gov ID No.: NCT00289237

FUNDING

The Danish Medical Research Council, the Danish Center for Evaluation and Health Technology Assessment, Novo Nordisk, Copenhagen County, the Danish Heart Foundation, the Danish Diabetes Association, the Danish Pharmaceutical Association, the Augustinus Foundation, the Ib Henriksen Foundation and the Becket Foundation.

Resistance exercise training lowers HbA1c more than aerobic training in adults with type 2 diabetes

BACKGROUND

The aim of this study was to compare the effects of 10 weeks of resistance or treadmill exercises on glycemic indices levels prior to and immediately following exercise in adults with type 2 diabetes.

RESEARCH DESIGN AND METHOD

Twenty inactive subjects (mean age 53.5 years) with type 2 diabetes enrolled in the study. Baseline HbA1c, blood glucose levels, heart rate, and blood pressure were measured for each subject prior to the initiation of the exercise program. Subsequently, subjects were matched to age, waist circumference and sex and assigned to either isocaloric resistance or treadmill exercise groups, which met 3 times per week for 10 weeks.

RESULTS

Both groups showed a reduction in pre and post-exercise blood glucose and HbA1c values. There was no change in resting blood pressure or heart rate in either group during the course of the 10 week intervention. The group receiving resistance exercises showed significant differences in the daily pre-exercise plasma glucose readings between the beginning and end of the exercise protocol (p < 0.001). There were significant improvements in the mean HbA1c reading pre and post training in both groups (p < 0.001). However, the greater reduction was noted in the resistance exercise group, and at 10 weeks their HbA1c levels were significantly lower than the group that received treadmill exercises (p < 0.006).

CONCLUSION

Ten weeks of resistance exercises were associated with a significantly better glycemic control in adults with type 2 diabetes compared to treadmill exercise.

Pathophysiology and aetiology of impaired fasting glycaemia and impaired glucose tolerance: does it matter for prevention and treatment of type 2 diabetes?

Prior to the development of type 2 diabetes, glucose levels increase into the prediabetic states of isolated impaired fasting glycaemia (i-IFG), isolated impaired glucose tolerance (i-IGT), or combined IFG/IGT. A better understanding of the aetiology and pathophysiology of the prediabetic states might give a basis for the development of individualised prevention and treatment strategies for type 2 diabetes. Several studies have examined mechanisms and potential aetiological factors leading to the development of the different prediabetic states. The pathophysiology of i-IFG seems to include the following key defects: reduced hepatic insulin sensitivity, stationary beta cell dysfunction and/or chronic low beta cell mass, altered glucagon-like peptide-1 secretion and inappropriately elevated glucagon secretion. Conversely, the prediabetic state i-IGT is characterised by reduced peripheral insulin sensitivity, near-normal hepatic insulin sensitivity, progressive loss of beta cell function, reduced secretion of glucose-dependent insulinotropic polypeptide and inappropriately elevated glucagon secretion. Individuals developing combined IFG/IGT exhibit severe defects in both peripheral and hepatic insulin sensitivity as well as a progressive loss of beta cell function. The aetiologies of i-IFG and i-IGT also seem to differ, with i-IFG being predominantly related to genetic factors, smoking and male sex, while i-IGT is predominantly related to physical inactivity, unhealthy diet and short stature. Since the transition from the prediabetic states to overt type 2 diabetes is characterised by a non-reversible vicious cycle that includes severe deleterious effects on glucose metabolism, there are good reasons to use the well-established aetiological and pathophysiological differences in i-IFG, i-IGT and IFG/IGT to design individualised preventive strategies.

Objectively measured moderate- and vigorous-intensity physical activity but not sedentary time predicts insulin resistance in high-risk individuals

OBJECTIVE

Low levels of physical activity appear to be associated with insulin resistance. However, the detailed associations of these complex relationships remain elusive. We examined the prospective associations between self-reported TV viewing time, objectively measured time spent sedentary, at light-intensity activity, and at moderate- and vigorous-intensity physical activity (MVPA) with insulin resistance.

RESEARCH DESIGN AND METHODS

In 192 individuals (81 men and 111 women) with a family history of type 2 diabetes, we measured physical activity and anthropometric and metabolic variables at baseline and after 1 year of follow-up in the ProActive UK trial. Physical activity was measured objectively by accelerometry. Insulin resistance was expressed as fasting insulin and the homeostasis model assessment score (HOMA-IR).

RESULTS

Baseline MVPA was a significant predictor of fasting insulin at follow-up (beta = -0.004 [95% CI -0.007 to -0.0001], P = 0.022), and the association approached significance for HOMA-IR (beta = -0.003 [-0.007 to 0.000002], P = 0.052), independent of time spent sedentary, at light-intensity activity, sex, age, smoking status, waist circumference, and self-reported TV viewing. Time spent sedentary and at light-intensity activity were not significantly associated with insulin resistance. The change in MVPA between baseline and follow-up was inversely related to fasting insulin (beta = -0.003 [-0.007 to -0.0003], P = 0.032) and the HOMA-IR score (beta = -0.004 [-0.008 to -0.001], P = 0.015) at follow-up, after adjustment for baseline phenotype in addition to the same confounders as above.

CONCLUSIONS

These results highlight the importance of promoting moderate-intensity activity such as brisk walking for improving insulin sensitivity and possibly other metabolic risk factors to prevent type 2 diabetes.

Predictors of future fasting and 2-h post-OGTT plasma glucose levels in middle-aged men and women-the Inter99 study

AIMS

Screening and prevention strategies for Type 2 diabetes require insight into the aetiological and potentially different risk factors leading to early impairments of fasting plasma glucose (FPG) and 2-h post-load plasma glucose (2hPG) levels. We studied whether risk factors predicting subtle elevations of FPG levels were different from those predicting elevations of 2hPG levels in men and women.

METHODS

We used baseline and 5-year follow-up data from middle-aged men and women with normal glucose tolerance (NGT) at baseline in the Danish population-based Inter99 study (n = 3164). Anthropometric and non-anthropometric baseline predictors of the 5-year FPG and 2hPG levels were estimated in linear regression models stratified by gender.

RESULTS

In men, but not in women, smoking and family history of diabetes predicted increased FPG levels, whereas high physical activity predicted a decline in 2hPG levels. Among the anthropometric variables, large waist circumference was the strongest predictor of increased FPG levels in men, whereas high body mass index (BMI) was the strongest predictor of increased FPG levels in women. In both men and women, BMI and waist circumference were equally strong in predicting 2hPG levels. Furthermore, short height predicted increased 2hPG levels in men, and short height and low hip circumference predicted increased 2hPG levels in women.

CONCLUSIONS

Risk factors that predict future FPG levels are different from those predicting future 2hPG levels. Furthermore, different risk factors predict glycaemic levels in men compared with women. These findings indicate that different aetiological pathways may lead to Type 2 diabetes in men and women.

Confusion and conflict in assessing the physical activity status of middle-aged men

BACKGROUND

Physical activity (including exercise) is prescribed for health and there are various recommendations that can be used to gauge physical activity status. The objective of the current study was to determine whether twelve commonly-used physical activity recommendations similarly classified middle-aged men as sufficiently active for general health.

METHODS AND FINDINGS

We examined the commonality in the classification of physical activity status between twelve variations of physical activity recommendations for general health in ninety men aged 45-64 years. Physical activity was assessed using synchronised accelerometry and heart rate. Using different guidelines but the same raw data, the proportion of men defined as active ranged from to 11% to 98% for individual recommendations (median 73%, IQR 30% to 87%). There was very poor absolute agreement between the recommendations, with an intraclass correlation coefficient (A,1) of 0.24 (95% CI, 0.15 to 0.34). Only 8% of men met all 12 recommendations and would therefore be unanimously classified as active and only one man failed to meet every recommendation and would therefore be unanimously classified as not sufficiently active. The wide variability in physical activity classification was explained by ostensibly subtle differences between the 12 recommendations for thresholds related to activity volume (time or energy), distribution (e.g., number of days of the week), moderate intensity cut-point (e.g., 3 vs. 4 metabolic equivalents or METs), and duration (including bout length).

CONCLUSIONS

Physical activity status varies enormously depending on the physical activity recommendation that is applied and even ostensibly small differences have a major impact. Approximately nine out of every ten men in the present study could be variably described as either active or not sufficiently active. Either the effective dose or prescription that underlies each physical activity recommendation is different or each recommendation is seeking the same prescriptive outcome but with variable success.

Sex differences in diabetes risk and the effect of intensive lifestyle modification in the Diabetes Prevention Program

OBJECTIVE

In participants of the Diabetes Prevention Program (DPP) randomized to intensive lifestyle modification (ILS), meeting ILS goals strongly correlated with prevention of diabetes in the group as a whole. Men met significantly more ILS goals than women but had a similar incidence of diabetes. Therefore, we explored sex differences in risk factors for diabetes and the effect of ILS on risk factors.

RESEARCH DESIGN AND METHODS

Baseline risk factors for diabetes and percent change in risk factors over the first year in men versus women were compared using Wilcoxon's rank-sum tests.

RESULTS

At baseline, men were older and had a larger waist circumference; higher fasting plasma glucose concentration, caloric intake, and blood pressure; and lower HDL cholesterol and corrected insulin response than women, who were less physically active and had a higher BMI (P < 0.01 for all comparisons). Over the first year of the DPP, no sex difference in risk factors for diabetes was observed for those who lost <3% body weight. Weight loss of 3-7% body weight yielded greater decreases in 2-h glucose (P < 0.01), insulin concentration (P < 0.04), and insulin resistance (P < 0.03) in men than in women. Weight loss of >7% body weight resulted in greater decreases in 2-h glucose (P < 0.01), triglyceride level (P < 0.01), and A1C (P < 0.03) in men than in women.

CONCLUSIONS

Weight loss >3% body weight yielded greater reduction in risk factors for diabetes in men than in women. Despite the more favorable effects of ILS in men, baseline risk factors were more numerous in men and likely obscured any sex difference in incident diabetes.

Impaired fasting glycaemia vs impaired glucose tolerance: similar impairment of pancreatic alpha and beta cell function but differential roles of incretin hormones and insulin action

AIMS/HYPOTHESIS

The impact of strategies for prevention of type 2 diabetes in isolated impaired fasting glycaemia (i-IFG) vs isolated impaired glucose tolerance (i-IGT) may differ depending on the underlying pathophysiology. We examined insulin secretion during OGTTs and IVGTTs, hepatic and peripheral insulin action, and glucagon and incretin hormone secretion in individuals with i-IFG (n = 18), i-IGT (n = 28) and normal glucose tolerance (NGT, n = 20).

METHODS

Glucose tolerance status was confirmed by a repeated OGTT, during which circulating insulin, glucagon, glucose-dependent insulinotrophic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) levels were measured. A euglycaemic-hyperinsulinaemic clamp with [3-3H]glucose preceded by an IVGTT was performed.

RESULTS

Absolute first-phase insulin secretion during IVGTT was decreased in i-IFG (p = 0.026), but not in i-IGT (p = 0.892) compared with NGT. Hepatic insulin sensitivity was normal in i-IFG and i-IGT individuals (p > or = 0.179). Individuals with i-IGT had peripheral insulin resistance (p = 0.003 vs NGT), and consequently the disposition index (DI; insulin secretion x insulin sensitivity) during IVGTT (DI(IVGTT))) was reduced in both i-IFG and i-IGT (p < 0.005 vs NGT). In contrast, the DI during OGTT (DI(OGTT)) was decreased only in i-IGT (p < 0.001), but not in i-IFG (p = 0.143) compared with NGT. Decreased levels of GIP in i-IGT (p = 0.045 vs NGT) vs increased levels of GLP-1 in i-IFG (p = 0.013 vs NGT) during the OGTT may partially explain these discrepancies. Basal and post-load glucagon levels were significantly increased in both i-IFG and i-IGT individuals (p < or = 0.001 vs NGT).

CONCLUSIONS/INTERPRETATION

We propose that differentiated preventive initiatives in prediabetic individuals should be tested, targeting the specific underlying metabolic defects.

Impaired fasting glycaemia vs impaired glucose tolerance: similar impairment of pancreatic alpha and beta cell function but differential roles of incretin hormones and insulin action

AIMS/HYPOTHESIS

The impact of strategies for prevention of type 2 diabetes in isolated impaired fasting glycaemia (i-IFG) vs isolated impaired glucose tolerance (i-IGT) may differ depending on the underlying pathophysiology. We examined insulin secretion during OGTTs and IVGTTs, hepatic and peripheral insulin action, and glucagon and incretin hormone secretion in individuals with i-IFG (n = 18), i-IGT (n = 28) and normal glucose tolerance (NGT, n = 20).

METHODS

Glucose tolerance status was confirmed by a repeated OGTT, during which circulating insulin, glucagon, glucose-dependent insulinotrophic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) levels were measured. A euglycaemic-hyperinsulinaemic clamp with [3-3H]glucose preceded by an IVGTT was performed.

RESULTS

Absolute first-phase insulin secretion during IVGTT was decreased in i-IFG (p = 0.026), but not in i-IGT (p = 0.892) compared with NGT. Hepatic insulin sensitivity was normal in i-IFG and i-IGT individuals (p > or = 0.179). Individuals with i-IGT had peripheral insulin resistance (p = 0.003 vs NGT), and consequently the disposition index (DI; insulin secretion x insulin sensitivity) during IVGTT (DI(IVGTT))) was reduced in both i-IFG and i-IGT (p < 0.005 vs NGT). In contrast, the DI during OGTT (DI(OGTT)) was decreased only in i-IGT (p < 0.001), but not in i-IFG (p = 0.143) compared with NGT. Decreased levels of GIP in i-IGT (p = 0.045 vs NGT) vs increased levels of GLP-1 in i-IFG (p = 0.013 vs NGT) during the OGTT may partially explain these discrepancies. Basal and post-load glucagon levels were significantly increased in both i-IFG and i-IGT individuals (p < or = 0.001 vs NGT).

CONCLUSIONS/INTERPRETATION

We propose that differentiated preventive initiatives in prediabetic individuals should be tested, targeting the specific underlying metabolic defects.

Determinants of progression from impaired fasting glucose and impaired glucose tolerance to diabetes in a high-risk screened population: 3 year follow-up in the ADDITION study, Denmark

AIMS/HYPOTHESIS

We sought to identify determinants of progression from impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) to diabetes in high-risk screened individuals.

METHODS

In general practices in Denmark, stepwise screening for type 2 diabetes mellitus in persons aged 40 to 69 years included a risk questionnaire, random blood glucose, HbA1c, fasting blood glucose and an OGTT. The 1,821 individuals with IGT or isolated IFG (WHO 1999) were re-invited after 1 and 3 years. Follow-up data on glucose measurements were available in 1,510 individuals and additional clinical data in 1,002 collected at the 3-year visits. Regression models using interval censoring were used.

RESULTS

Progression rates from IFG and IGT to diabetes over 3.5 years were 11.8 and 17.0 per 100 person-years, respectively and were particularly high in the first year. Baseline determinants of progression were: IFG: glucose measures, BMI [per kg/m2, rate ratio (RR) 1.04 (95% CI, 1.01-1.08)] and triacylglycerol [per twofold increase, RR 2.19 (1.49-3.22)]; and IGT: glucose measures and known hypertension [RR 1.46 (1.11-1.93)]. Weight reduction and decreased triacylglycerol were inversely associated with development of diabetes in IFG individuals [per 1 kg/year, RR 0.81 (0.66-0.98) and per 1 mmol l(-1) year(-1), RR 0.08 (0.01-0.51), respectively], whereas in IGT participants only weight reduction was inversely associated [per 1 kg/year, RR 0.80 (0.67-0.96)].

CONCLUSIONS/INTERPRETATION

Higher levels of glucose measures, larger BMI, known hypertension and hypertriacylglycerolaemia are significant determinants of progression in high-risk screened individuals. Weight loss of 1 kg/year or reduction of hypertriacylglycerolaemia markedly reduced the risk of diabetes.

Objectively measured sedentary time, physical activity, and metabolic risk: the Australian Diabetes, Obesity and Lifestyle Study (AusDiab)

OBJECTIVE

We examined the associations of objectively measured sedentary time and physical activity with continuous indexes of metabolic risk in Australian adults without known diabetes.

RESEARCH DESIGN AND METHODS

An accelerometer was used to derive the percentage of monitoring time spent sedentary and in light-intensity and moderate-to-vigorous-intensity activity, as well as mean activity intensity, in 169 Australian Diabetes, Obesity and Lifestyle Study (AusDiab) participants (mean age 53.4 years). Associations with waist circumference, triglycerides, HDL cholesterol, resting blood pressure, fasting plasma glucose, and a clustered metabolic risk score were examined.

RESULTS

Independent of time spent in moderate-to-vigorous-intensity activity, there were significant associations of sedentary time, light-intensity time, and mean activity intensity with waist circumference and clustered metabolic risk. Independent of waist circumference, moderate-to-vigorous-intensity activity time was significantly beneficially associated with triglycerides.

CONCLUSIONS

These findings highlight the importance of decreasing sedentary time, as well as increasing time spent in physical activity, for metabolic health.

Objectively measured light-intensity physical activity is independently associated with 2-h plasma glucose

OBJECTIVE

We examined the associations of objectively measured sedentary time, light-intensity physical activity, and moderate- to vigorous-intensity activity with fasting and 2-h postchallenge plasma glucose in Australian adults.

RESEARCH DESIGN AND METHODS

A total of 67 men and 106 women (mean age +/- SD 53.3 +/- 11.9 years) without diagnosed diabetes were recruited from the 2004-2005 Australian Diabetes, Obesity, and Lifestyle (AusDiab) study. Physical activity was measured by Actigraph accelerometers worn during waking hours for 7 consecutive days and summarized as sedentary time (accelerometer counts/min <100; average hours/day), light-intensity (counts/min 100-1951), and moderate- to vigorous-intensity (counts/min > or =1,952). An oral glucose tolerance test was used to ascertain 2-h plasma glucose and fasting plasma glucose.

RESULTS

After adjustment for confounders (including waist circumference), sedentary time was positively associated with 2-h plasma glucose (b = 0.29, 95% CI 0.11-0.48, P = 0.002); light-intensity activity time (b = -0.25, -0.45 to -0.06, P = 0.012) and moderate- to vigorous-intensity activity time (b = -1.07, -1.77 to -0.37, P = 0.003) were negatively associated. Light-intensity activity remained significantly associated with 2-h plasma glucose following further adjustment for moderate- to vigorous-intensity activity (b = -0.22, -0.42 to -0.03, P = 0.023). Associations of all activity measures with fasting plasma glucose were nonsignificant (P > 0.05).

CONCLUSIONS

These data provide the first objective evidence that light-intensity physical activity is beneficially associated with blood glucose and that sedentary time is unfavorably associated with blood glucose. These objective data support previous findings from studies using self-report measures, and suggest that substituting light-intensity activity for television viewing or other sedentary time may be a practical and achievable preventive strategy to reduce the risk of type 2 diabetes and cardiovascular disease.

Association of television viewing with fasting and 2-h postchallenge plasma glucose levels in adults without diagnosed diabetes

OBJECTIVE

We examined the associations of television viewing time with fasting plasma glucose (FPG) and 2-h postchallenge plasma glucose (2-h PG) levels in Australian adults.

RESEARCH DESIGN AND METHODS

A total of 8,357 adults aged > 35 years who were free from diagnosed diabetes and who attended a population-based cross-sectional study (Australian Diabetes, Obesity and Lifestyle Study [AusDiab]) were evaluated. Measures of FPG and 2-h PG were obtained from an oral glucose tolerance test. Self-reported television viewing time (in the previous week) was assessed using an interviewer-administered questionnaire. Homeostasis model assessment (HOMA) of insulin sensitivity (HOMA-%S) and beta-cell function (HOMA-%B) were calculated based on fasting glucose and insulin concentrations.

RESULTS

After adjustment for confounders and physical activity time, time spent watching television in women was positively associated with 2-h PG, log fasting insulin, and log HOMA-%B and inversely associated with log HOMA-%S (P < 0.05) but not with FPG. No significant associations were observed with glycemic measures in men. The beta-coefficients across categories of average hours spent watching television per day (< 1.0, 1.0-1.9, 2.0-2.9, 3.0-3.9, and > or = 4.0) for 2-h PG in women were 0 (reference), 0.009, 0.047, 0.473, and 0.501, respectively (P for trend = 0.02).

CONCLUSIONS

Our findings highlight the unique deleterious relationship of sedentary behavior (indicated by television viewing time) and glycemic measures independent of physical activity time and adiposity status. These relationships differed according to sex and type of glucose measurement, with the 2-h PG measure being more strongly associated with television viewing. The findings suggest an important role for reducing sedentary behavior in the prevention of type 2 diabetes and cardiovascular disease, especially in women.