The association of intensity and overall level of physical activity energy expenditure with a marker of insulin resistance

The effect of metformin treatment on volumes of free-living physical activity and sedentary behaviour: A post-hoc analysis of the PRE-D trial

Perceived physical exertion is increased when exercise is performed on metformin treatment, but the clinical relevance of this is unknown. In this post hoc analysis of a randomized, controlled trial, we investigated whether metformin treatment was associated with lower levels of free-living physical activity.   Ninety individuals with overweight/obesity (BMI>25 m2/kg) and HbA1c-defined prediabetes (39-47 mmol/mol) were randomized to treatment with dapagliflozin (SGLT2-inhibitor; 10 mg once daily, n=30), metformin (850 mg twice daily, n=30) or no treatment (control, n=30) for 13 weeks in a parallel-group, open-label trial. Before (baseline), during (6 weeks) and immediately after (13 weeks) cessation of treatment, a 6-day assessment of physical activity and sedentary behaviour was performed using accelerometer-based physical activity monitors. Intention-to-treat analyses revealed no within-group changes or differences in change between the groups for any measures of physical activity or sedentary behaviour at neither 6 nor 13 weeks. Short-term metformin treatment does not reduce free-living physical activity level in individuals with overweight/obesity and HbA1c-defined prediabetes.

Impact of pre- and post-diagnosis physical activity on the mortality of patients with cancer: Results from the Health Examinees-G study in Korea

BACKGROUND

Physical activity (PA) is recommended to improve the survival of cancer patients. However, the prognostic impact of specific PAs is not well understood. Therefore, we investigated the associations of the duration, type, intensity, and number of PAs one participates in pre- and post-diagnosis with mortality in Korean patients with cancer.

METHODS

Among the participants aged 40-69 years recruited from the Health Examines study, those diagnosed with cancer after baseline (n = 7749) and within 10 years before baseline (n = 3008) were included in the analyses for pre- and post-diagnosis PA, respectively. Duration, intensity, type, and number of leisure-time physical activities participated in were assessed using questionnaires. The Cox proportional hazard model was used to characterize the association between PA and cancer-specific mortality, adjusting for demographics, behaviors, comorbidities, and cancer stage based on the Surveillance, Epidemiology, and End Results program.

RESULTS

Pre-diagnosis, patients participating in vigorous-intensity activities (hazard ratio [HR]: 0.70, 95% confidence interval [CI]: 0.61-0.82), walking (HR: 0.85, 95% CI: 0.74-0.97), climbing (HR: 0.65, 95% CI: 0.55-0.77), sports (HR: 0.39, 95% CI: 0.25-0.61), and more than two activities (HR: 0.73, 95% CI: 0.63-0.86) had significantly lower all-cause mortality. Importantly, these associations were only found in patients with colorectal cancer participating in vigorous-intensity activities (HR: 0.40, 95% CI: 0.23-0.70). Post-diagnosis, only patients who performed more than two activities (HR: 0.65, 95% CI: 0.44-0.95) had significantly lower all-cause mortality. Similar associations were found for cancer mortality, both pre- and post-diagnosis.

CONCLUSION

Specific characteristics of PA pre- and post-diagnosis may influence the survival of cancer patients.

Association between sedentary behavior and chronic kidney disease in Korean adults

BACKGROUND

Chronic kidney disease (CKD) is a significant health care burden, with a worldwide prevalence of approximately 11%. The general population spends over 50% of the awake time sedentary activities. However, to the best of our knowledge, no study has evaluated the association between sedentary time and CKD, with a focus on both kidney damage and kidney function, in the South Korean population. Accordingly, the present study aimed to address this gap in the knowledge.

METHOD

We used data from the 8^th Korea National Health and Nutrition Examination Survey. The analysis included 9,534 participants, especially excluded those who had been diagnosed with kidney disease or who were currently undergoing treatment. Sedentary behavior was self-reported by the participants. An estimated glomerular filtration rate (eGFR) and/or albuminuria were used as measures for detection of CKD according to the guidelines of the Kidney Disease Improving Global Outcomes. We analyzed the data using multiple logistic regression.

RESULTS

Among the women, the risk of CKD was significantly greater among those who sat for ≥ 12 h/d relative to those who sat for < 6 h/d, after adjusting for physical activity and other covariates (odds ratio [OR]: 1.45, 95% confidence interval [CI]: 1.01-2.06). Similarly, among those who sat over 12 h/d, those who engaged in low levels of physical activity had a higher risk of CKD than those who engaged in high levels of activity (OR: 1.65, 95% CI: 1.04-2.61). No statistically significant results were found for men.

CONCLUSION

Excessive sedentary behavior was associated with an increased risk of CKD, especially albuminuria, regardless of the level of physical activity, only in women. These findings emphasize the importance of avoiding excessive sitting for a long time and increasing overall physical activity levels.

Isotemporal Substitution of Time Between Sleep and Physical Activity: Associations With Cardiovascular Risk Factors in Early Rheumatoid Arthritis

OBJECTIVE

We aimed to determine relationships between objectively measured nightly sleep, sedentary behavior (SB), light physical activity (LPA), and moderate to vigorous physical activity (MVPA) with risk factors for cardiovascular disease (CVD) in patients with early rheumatoid arthritis (RA). Furthermore, we aimed to estimate consequences for these risk factors of theoretical displacements of 30 minutes per day in one behavior with the same duration of time in another.

METHODS

This cross-sectional study included 78 patients with early RA. Nightly sleep, SB, LPA, and MVPA were assessed by a combined heart rate and accelerometer monitor. Associations with risk factors for CVD were analyzed using linear regression models and consequences of reallocating time between the behaviors by isotemporal substitution modeling.

RESULTS

Median (Q1-Q3) nightly sleep duration was 4.6 (3.6-5.8) hours. Adjusted for monitor wear time, age, and sex, 30-minutes-longer sleep duration was associated with favorable changes in the values β (95% confidence interval [CI]) for waist circumference by -2.2 (-3.5, -0.9) cm, body mass index (BMI) by -0.9 (-1.4, -0.4) kg/m2 , body fat by -1.5 (-2.3, -0.8)%, fat-free mass by 1.6 (0.8, 2.3)%, sleeping heart rate by -0.8 (-1.5, -0.1) beats per minute, and systolic blood pressure by -2.5 (-4.0, -1.0) mm Hg. Thirty-minute decreases in SB, LPA, or MVPA replaced with increased sleep was associated with decreased android fat and lower systolic blood pressure levels. Replacement of SB or LPA with MVPA yielded lower BMIs.

CONCLUSION

Shorter sleep during the night is common among patients with early RA and is associated with adverse risk factors for CVD.

The association between sedentary behavior, physical activity and hyperuricemia

Background

A significant discovery was recently made in which participation in physical activity and sedentary behavior, two contrasting lifestyles, was found to be related to the frequency of hyperuricemia diagnosis. The purpose of this study was to identify the association between sedentary behavior and physical activity levels in South Korean men and women diagnosed with hyperuricemia.

Methods

This study included 161,064 healthy men and women participants who had obtained a complete health examination. Physical activity levels and sitting time were assessed by the validated International Physical Activity Questionnaire Short Form Korean version. The presence of hyperuricemia in the subjects was determined by measuring serum uric acid (SUA) concentration (SUA ≥6 mg/dL [male], SUA ≥7 mg/dL [female]). Logistic regression analysis, adjusting other confounding factors, was conducted to identify the association of sedentary behavior and physical activity levels with hyperuricemia (p<0.05).

Results

Subjects who spent ≥10 hr/day in sedentary behavior were more likely to have hyperuricemia than those who spent <5 hour/day in sedentary behavior (OR=1.08, 95% CI=1.03–1.12). The subject group that more frequently participated in health enhanced physical activity (HEPA) had a lower hyperuricemia odds ratio than the subject group with lower physical activity participation rate (OR=0.90, 95% Ci=0.86–0.93). From the analysis of sex (male, female), age (young, middle, older), methods of measuring obesity (body mass index, waist circumference, body fat percentage), the association of sedentary behavior and physical activity levels with hyperuricemia was shown differently in different multivariable models.

Conclusion

Participation in regular physical activity and reduced sedentary time is highly recommended in order to reduce the prevalence of hyperuricemia.

Contribution of lower physical activity levels to higher risk of insulin resistance and associated metabolic disturbances in South Asians compared to Europeans

BACKGROUND

Insulin resistance and related metabolic disturbances are major risk factors for the higher T2D risk and associated morbidity and mortality amongst South Asians. The contribution of physical activity to the increased prevalence of insulin resistance and related disturbances amongst South Asians is unknown.

METHODS

We recruited 902 South Asian and European men and women, aged 35-85 years from the ongoing LOLIPOP study. Clinical characterisation comprised standardised questionnaire and measurement of height, weight, waist and hip circumference and blood pressure. Fasting bloods were taken for assessment of glucose, insulin, lipids and HbA1c. Physical activity was quantified using a validated accelerometer, Actigraph GT3X+, worn for 7 days. Univariate and multivariate approaches were used to investigate the relationship between ethnicity, physical activity, insulin resistance and related metabolic disturbances.

RESULTS

Total physical activity was ~31% (P = 0.01) lower amongst South Asians compared to Europeans (Mean MET.minutes [SD]: 1505.2 [52] vs. 2050.9 [86.6], P<0.001). After adjusting for age and sex, total physical activity had a negative association with HOMA-IR (B [SE]: -0.18 [0.08], P = 0.04) and fasting glucose levels (B[SE]: -0.11 [0.04], P = 0.02). There was no association between physical activity and other glycemic and lipid parameters. Total physical activity per week contributed towards the differences in insulin resistance and associated metabolic disturbances between South Asians and Europeans.

CONCLUSION

Lower levels of physical activity may contribute to the increased insulin resistance in South Asians compared to Europeans. Our results suggest that lifestyle modification through increased physical activity may help to improve glucose metabolism and reduce the burden of excess T2D and related complications amongst South Asians.

The effectiveness of high intensity intermittent training on metabolic, reproductive and mental health in women with polycystic ovary syndrome: study protocol for the iHIT- randomised controlled trial

BACKGROUND

Polycystic ovary syndrome (PCOS) is a reproductive-metabolic condition. Insulin resistance is a hallmark of PCOS and is related to increased hyperandrogenism that drives inherent metabolic, reproductive and psychological features of the syndrome. Insulin resistance in women with PCOS is managed by weight loss, lifestyle interventions (i.e. exercise, diet) and insulin-sensitising medications. This manuscript describes the protocol of our study evaluating the effectiveness of high intensity intermittent training (HIIT) or moderate intensity exercise on cardiometabolic, reproductive and mental health in overweight women with PCOS.

METHODS/DESIGN

We will employ a three arm, parallel-group, randomised controlled trial recruiting 60 women diagnosed with PCOS, aged between 18 and 45 years and with a body mass index (BMI) greater than 25 kg/m2. Following screening and baseline testing, women will be randomised by simple randomisation procedure using computer generated sequence allocation to undergo one of two 12-week supervised interventions: either HIIT or moderate intensity exercise (standard supervised exercise), or to standard care [Con] (unsupervised lifestyle advice) at a 1:1:1 allocation ratio. The primary outcome for this trial is to measure the improvements in metabolic health; specifically changes in insulin sensitivity in response to different exercise intensities. Baseline and post-intervention testing include anthropometric measurements, cardiorespiratory fitness testing, reproductive hormone profiles (anti-müllerian hormone and steroid profiles), metabolic health, health-related quality of life and mental health questionnaires and objective and subjective lifestyle monitoring. Reporting of the study will follow the CONSORT statement.

DISCUSSION

This trial aims to demonstrate the comparative efficacy and maintenance of different exercise intensities to advance the understanding of PCOS management and provide insight into the optimal exercise intensity for improved cardiometabolic outcomes. Secondary outcomes will include the impact of different exercise protocols on reproductive hormone profiles, mental health and health-related quality of life.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry, ACTRN12615000242527 . Registered on 17 March 2015.

Association of self-reported sedentary time with insulin resistance among Korean adults without diabetes mellitus: a cross-sectional study

Background

A more sedentary lifestyle can result in insulin resistance. However, few research studies have assessed the association between insulin resistance and sedentary lifestyle in Asian populations. Therefore, this study aimed to investigate the association of sedentary time with insulin resistance. In addition, we also investigate the moderate effect of employment status, moderate-to-vigorous physical activity (MVPA), and body mass index (BMI) in this association.

Methods

Data from 2573 individuals who participated in the 2015 Korean National Health and Nutrition Examination Survey were analyzed. Sedentary time was measured using self-administered questionnaires, and IR data were estimated using the homeostasis model assessment–insulin resistance index (HOMA-IR). Adjusted odds ratio (OR) and 95% confidence intervals (CIs) from a multivariable logistic regression model were generated for all participants. Subgroup analysis was only performed between sedentary time and HOMA-IR stratified by employment status, because moderate effects were not significant in the tests for interaction for MVPA and BMI. For all analyses, the individuals were categorized as having high or normal HOMA-IR values (> 1.6 and ≤ 1.6, respectively).

Results

A HOMA-IR > 1.6 was observed in 40.3% of the sedentary time Q1 (low) group (< 5.0 h/day), 41.4% of the sedentary time Q2 (middle-low) group, 44.2% of the sedentary time Q3 (middle-high) group, and 48.4% of the sedentary time Q4 (high) group (≥10.0 h/day). When the low level sedentary time group was used as the reference group, the high level sedentary time group was significantly associated with high IR value (HOMA-IR > 1.6) (OR = 1.40, 95% CI: 1.060–1.838). However, this association was not significant across the other sedentary time groups. Moreover, participants reporting a high sedentary time and were employed had 1.67 times the odds of having a high IR value (HOMA-IR > 1.6) compared to those who reported having a low sedentary time and were employed (OR = 1.67, 95% CI: 1.184–2.344). In the unemployed participants, sedentary time was not associated with IR.

Conclusions

High sedentary time (≥10.0 h/day) was associated with elevated HOMA-IR among Korean adults without diabetes mellitus. Furthermore, the association between high sedentary time and HOMA-IR values was more pronounced in the employed population.

Light-Intensity Physical Activity and Cardiometabolic Risk Among Older Adults With Multiple Chronic Conditions

PURPOSE

To assess the relationship between light-intensity physical activity (LIPA) and cardiometabolic risk factors among middle-aged and older adults with multiple chronic conditions.

DESIGN

Cross-sectional design utilizing data from the Health and Retirement Study (2010, 2012).

SETTING

Laboratory- and survey-based testing of a nationally representative sample of community-dwelling middle aged and older adults.

PARTICIPANTS

Adults aged 50 years and older (N = 14 996).

MEASURES

Weighted metabolic equivalent of tasks was calculated using self-reported frequency of light, moderate, and vigorous physical activity. Cardiometabolic risk factors (systolic and diastolic blood pressure, glycosylated hemoglobin [HbA_1c], high-density lipoprotein cholesterol [HDL-C], total cholesterol, and non-HDL-C) were objectively measured. A multiple chronic condition index was based on 8 self-reported chronic conditions.

ANALYSIS

Weighted multivariate linear regression models.

RESULTS

Light-intensity physical activity was independently associated with favorable HDL-C (β = 1.25; 95% confidence interval [CI]: 0.46-2.05) and total cholesterol (β = 2.72; 95% CI: 0.53-4.90) after adjusting for relevant confounders. The HDL-C health benefit was apparent when stratified by number of chronic conditions, for individuals with 2 to 3 conditions (β = 1.73; 95% CI: 0.58-2.89). No significant associations were observed between LIPA and blood pressure, HbA_1c, or non-HDL-C.

CONCLUSIONS

Engaging in LIPA may be an important health promotion activity to manage HDL-C and total cholesterol. Additional longitudinal research is needed to determine the causal association between LIPA and cardiometabolic risk which can potentially inform physical activity guidelines targeting older adults with multiple chronic conditions.

Physical Activity Dimensions Associated with Impaired Glucose Metabolism

PURPOSE

Physical activity (PA) is important in the prevention of Type 2 diabetes, yet little is known about the role of specific dimensions of PA, including sedentary time in subgroups at risk for impaired glucose metabolism (IGM). We applied a data-driven decision tool to identify dimensions of PA associated with IGM across age, sex, and body mass index (BMI) groups.

METHODS

This cross-sectional study included 1501 individuals (mean (SD) age, 65.6 (6.8) yr) at high risk for Type 2 diabetes from the ADDITION-PRO study. PA was measured by an individually calibrated combined accelerometer and heart rate monitor worn for 7 d. PA energy expenditure, time spent in different activity intensities, bout duration, and sedentary time were considered determinants of IGM together with age, sex, and BMI. Decision tree analysis was applied to identify subgroup-specific dimensions of PA associated with IGM. IGM was based on oral glucose tolerance test results and defined as a fasting plasma glucose level of ≥6.1 mmol·L and/or a 2-h plasma glucose level of ≥7.8 mmol·L.

RESULTS

Among overweight (BMI ≥25 kg·m) men, accumulating less than 30 min·d of moderate-to-vigorous PA was associated with IGM, whereas among overweight women, sedentary time was associated with IGM. Among individuals older than 53 yr with normal weight (BMI <25 kg·m), time spent in light PA was associated with IGM. None of the dimensions of PA were associated with IGM among individuals ≤53 yr of age with normal weight.

CONCLUSIONS

We identified subgroups in which different activity dimensions were associated with IGM. Methodology and results from this study may suggest a preliminary step toward the goal of tailoring and targeting PA interventions aimed at Type 2 diabetes prevention.

A longitudinal study of sleep duration in pregnancy and subsequent risk of gestational diabetes: findings from a prospective, multiracial cohort

BACKGROUND

Both short and prolonged sleep duration have been linked to impaired glucose metabolism. Sleep patterns change during pregnancy, but prospective data are limited on their relation to gestational diabetes.

OBJECTIVE

We sought to prospectively examine the trimester-specific (first and second trimester) association between typical sleep duration in pregnancy and subsequent risk of gestational diabetes, as well as the influence of compensatory daytime napping on this association.

STUDY DESIGN

In the prospective, multiracial Eunice Kennedy Shriver National Institute of Child Health and Human Development Fetal Growth Studies-Singleton Cohort, 2581 pregnant women reported their typical sleep duration and napping frequency in the first and second trimesters. Diagnosis of gestational diabetes (n = 107; 4.1%) was based on medical records review. Adjusted relative risks with 95% confidence intervals for gestational diabetes were estimated with Poisson regression, adjusting for demographics, prepregnancy body mass index, and other risk factors.

RESULTS

From the first and second trimester, sleep duration and napping frequency declined. Sleeping duration in the second but not first trimester was significantly related to risk of gestational diabetes. The association between second-trimester sleep and gestational diabetes differed by prepregnancy obesity status (P for interaction = .04). Among nonobese but not obese women, both sleeping >8-9 hours or <8-9 hours were significantly related to risk of gestational diabetes: 5-6 hours (adjusted relative risk, 2.52; 95% confidence interval, 1.27-4.99); 7 hours (adjusted relative risk, 2.01; 95% confidence interval, 1.09-3.68); or ≥10 hours (adjusted relative risk, 2.17; 95% confidence interval, 1.01-4.67). Significant effect modification by napping frequency was also observed in the second trimester (P for interaction = .03). Significant and positive association between reduced sleep (5-7 hours) and gestational diabetes was observed among women napping rarely/never (adjusted relative risk, 2.48; 95% confidence interval, 1.20-5.13), whereas no comparable associations were observed among women napping most/sometimes.

CONCLUSION

Our data suggest a U-shaped association between sleep duration and gestational diabetes, and that napping and prepregnancy obesity status may modify this association.

Long-term physical activity: an exogenous risk factor for sporadic amyotrophic lateral sclerosis?

OBJECTIVES

To conduct a geographically defined, UK-based case-control study, to examine any association between physical activity (PA) and amyotrophic lateral sclerosis (ALS).

METHODS

A novel historical PA questionnaire was designed, validated, and subsequently administered in individual face-to-face interviews of 175 newly diagnosed sporadic ALS cases and 317 age- and sex-matched community controls. Historical PA energy expenditure and time spent in vigorous-intensity PA were derived from questionnaire data and compared between cases and controls.

RESULTS

Participation in an extra 10kJ/kg/day of PA (equivalent to approximately 45minutes brisk walking) was consistently associated with an increased risk of ALS, with the strongest association observed for adulthood exercise-related PA (OR 1.47, 95% CI 1.10-1.97). An extra 10mins/day of vigorous PA was also associated with the odds of ALS (OR 1.03, 95% CI 1·01-1·05). Results were slightly attenuated following adjustment for smoking and educational attainment.

CONCLUSIONS

To our knowledge this is the first study to demonstrate a positive association between ALS and PA participation using a specifically designed and validated historical PA questionnaire. Despite the well-established health benefits of PA, a high activity lifestyle may also be associated with elevated risk of ALS. Large-scale prospective studies in the future may help to confirm this association.

Hair dye use, regular exercise, and the risk and prognosis of prostate cancer: multicenter case-control and case-only studies

Background

This study investigated the effects that hair dye use and regular exercise exert on the risk and prognosis of prostate cancer.

Methods

We studied 296 cases of histologically confirmed prostate cancer and 296 age- (in 2-y bands), ethnicity-, and hospital-matched controls in Taiwan between August 2000 and December 2008. To determine the rate of prostate cancer survival, another 608 incident prostate cancer cases occurring between August 2000 and December 2007 were investigated. Information on hair dye use and regular exercise was obtained using a standardized questionnaire.

Results

The use of hair dyes was associated with a significant 2.15-fold odds of developing prostate cancer (adjusted odds ratio = 2.15, 95 % confidence interval [CI] = 1.32–3.57), but was not associated with prostate cancer survival, compared with no use. The significant risks were more prominent in users aged < 60 years who had used hair dyes for > 10 years, > 6 times per year, and started using hair dyes before 1980. By contrast, regular exercise significantly reduced the number of prostate-cancer-specific death (adjusted hazard ratio = 0.37, 95 % CI = 0.16–0.83); the protective effect of exercise was more prominent among cancer patients who exercised daily (≥7 times/week). However, exercise could not prevent the development of prostate cancer.

Conclusions

Hair dye use increased the risk of prostate cancer, whereas regular exercise reduced the number of prostate-cancer-specific deaths.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2280-7) contains supplementary material, which is available to authorized users.

Impact of Physical Activity on Glycemic Control and Insulin Resistance: A Study of Community-dwelling Diabetic Patients in Eastern China

Objective The aim of this study was to evaluate the relationship of various intensities of physical activity with glycemic control and insulin resistance in eastern China. Methods A population-based, cross-sectional study was conducted in eastern China. The subjects included 604 community-dwelling people. The participants were classified as insufficiently active (IA); sufficiently active (SA) and very active (VA) according to the International Physical Activity Questionnaire (IPAQ). Insulin sensitivity was assessed using the homeostasis model assessment of insulin resistance (HOMA-IR). Related social, biological, lifestyle factors and clinical characteristics were recorded and used as potential confounders. Results The cohort of 604 type 2 diabetes patients were classified according to the activity level: 107 subjects who were classified as IA, 329 met the criteria for SA, and the rest were VA. The proportion of obese patients, smokers, patients with hypertension, and the body weight, body mass index (BMI), waist circumference, hemoglobin A1c protein (HbA1c), and 2-h postprandial blood glucose (2hPG) were significantly lower in the SA and VA groups than in the IA group (p<0.05 or 0.01). The SA group had lower levels of fasting blood glucose (FPG) and HOMA-IR than the IA and VA groups (p<0.05 or 0.01). HOMA-IR was positively correlated with FPG, 2hPG, HbA1c, waist circumference and BMI. HOMA-IR was negatively correlated with the total walking activity (p<0.05). After adjusting for FPG, 2hPG, HbA1c, waist circumference and BMI among the groups, a partial correlation analysis showed a correlation between HOMA-IR and the total walking activity. Conclusion Physical activity is a significant factor regarding glycemic control and insulin sensitivity, although SA and walking may be superior to VA for ameliorating insulin sensitivity.

Vigorous exercise is associated with superior metabolic profiles in polycystic ovary syndrome independent of total exercise expenditure

OBJECTIVE

To characterize metabolic features of women with polycystic ovary syndrome (PCOS) by exercise behavior and determine relative health benefits of different exercise intensities.

DESIGN

Cross-sectional study.

SETTING

Tertiary academic institution.

PATIENT(S)

Three hundred and twenty-six women aged 14-52 years-old with PCOS by Rotterdam criteria examined between 2006 and 2013.

INTERVENTION(S)

International Physical Activity Questionnaire (IPAQ) administered to classify patients into three groups based on Department of Health and Human Services (DHHS) Guidelines of vigorous, moderate, and inactive, along with physical examination and serum testing.

MAIN OUTCOME MEASURE(S)

Blood pressure, body mass index (BMI), waist circumference, fasting lipids, fasting glucose and insulin, 2-hour 75-gram oral glucose tolerance, homeostatic model assessment of insulin resistance (HOMA-IR).

RESULT(S)

The DHHS guidelines for adequate physical activity were met by 182 (56%) women. Compared with moderate exercisers and inactive women, the vigorous exercisers had lower BMI and lower HOMA-IR; higher levels of high-density lipoprotein cholesterol and sex hormone-binding globulin; and a reduced prevalence of the metabolic syndrome. In a multivariate logistic regression analysis controlling for age, BMI, and total energy expenditure, every hour of vigorous exercise reduced a patient's odds of metabolic syndrome by 22% (odds ratio 0.78; 95% confidence interval, 0.62, 0.99).

CONCLUSION(S)

Women with PCOS who met DHHS guidelines for exercise demonstrated superior metabolic health parameters. Vigorous but not moderate activity is associated with reduced odds of the metabolic syndrome, independent of age, BMI, and total energy expenditure. PCOS patients should be encouraged to meet activity guidelines via vigorous physical activity.

Estimation of Free-Living Energy Expenditure by Heart Rate and Movement Sensing: A Doubly-Labelled Water Study

Background

Accurate assessment of energy expenditure (EE) is important for the study of energy balance and metabolic disorders. Combined heart rate (HR) and acceleration (ACC) sensing may increase precision of physical activity EE (PAEE) which is the most variable component of total EE (TEE).

Objective

To evaluate estimates of EE using ACC and HR data with or without individual calibration against doubly-labelled water (DLW) estimates of EE.

Design

23 women and 23 men (22–55 yrs, 48–104 kg, 8–46%body fat) underwent 45-min resting EE (REE) measurement and completed a 20-min treadmill test, an 8-min step test, and a 3-min walk test for individual calibration. ACC and HR were monitored and TEE measured over 14 days using DLW. Diet-induced thermogenesis (DIT) was calculated from food-frequency questionnaire. PAEE (TEE ÷ REE ÷ DIT) and TEE were compared to estimates from ACC and HR using bias, root mean square error (RMSE), and correlation statistics.

Results

Mean(SD) measured PAEE and TEE were 66(25) kJ·day^-1·kg^-1, and 12(2.6) MJ·day^-1, respectively. Estimated PAEE from ACC was 54(15) kJ·day^-1·kg^-1 (p<0.001), with RMSE 24 kJ·day^-1·kg^-1 and correlation r = 0.52. PAEE estimated from HR and ACC+HR with treadmill calibration were 67(42) and 69(25) kJ·day^-1·kg^-1 (bias non-significant), with RMSE 34 and 20 kJ·day^-1·kg^-1 and correlations r = 0.58 and r = 0.67, respectively. Similar results were obtained with step-calibrated and walk-calibrated models, whereas non-calibrated models were less precise (RMSE: 37 and 24 kJ·day^-1·kg^-1, r = 0.40 and r = 0.55). TEE models also had high validity, with biases <5%, and correlations r = 0.71 (ACC), r = 0.66–0.76 (HR), and r = 0.76–0.83 (ACC+HR).

Conclusions

Both accelerometry and heart rate may be used to estimate EE in adult European men and women, with improved precision if combined and if heart rate is individually calibrated.

Physical activity and pre-diabetes-an unacknowledged mid-life crisis: findings from NHANES 2003-2006

The prevalence of pre-diabetes (PD) among US adults has increased substantially over the past two decades. By current estimates, over 34% of US adults fall in the PD category, 84% of whom meet the American Diabetes Association’s criteria for impaired fasting glucose (IFG). Low physical activity (PA) and/or sedentary behavior are key drivers of hyperglycemia. We examined the relationship between PD and objectively measured PA in NHANES 2003–2006 of 20,470 individuals, including 7,501 individuals between 20 and 65 yrs.We excluded all participants without IFG measures or adequate accelerometry data (final N = 1,317). Participants were identified as PD if FPG was 100–125 mg/dL (5.6–6.9 mmol/L). Moderate and vigorous PA in minutes/day individuals were summed to create the exposure variable “moderate-vigorous PA” (MVPA). The analysis sample included 884 normoglycemic persons and 433 with PD. There were significantly fewer PD subjects in the middle (30.3%) and highest (24.6%) tertiles of PA compared to the lowest tertile (35.5%). After adjusting for BMI, participants were 0.77 times as likely to be PD if they were in the highest tertile compared to the lowest PA tertile (p < 0.001). However, these results were no longer significant when age and BMI were held constant. Univariate analysis revealed that physical activity was associated with decreased fasting glucose of 0.5 mg/dL per minute of MVPA, but multivariate analysis adjusting for age and BMI was not significant. Overall, our data suggest a negative association between measures of PA and the prevalence of PD in middle-aged US adults independent of adiposity, but with significant confounding influence from measures of BMI and age.

Volume and intensity of physical activity in a large population-based cohort of middle-aged and older Australians: prospective relationships with weight gain, and physical function

OBJECTIVES

To examine prospectively whether higher proportions of vigorous physical activity (VPA), independent of total activity volume, are associated with better outcomes in weight maintenance and physical function.

METHODS

We used three-year longitudinal data (2006/07-2009/10) of adults 45 and older (n=32,087; 59.5±9.3years) from New South Wales, Australia. Logistic regression models examined odds of weight gain and functional decline by volume and intensity of physical activity.

RESULTS

On average, body weight increased by 0.66kg (SD=5.83, p<0.001); a validated physical function score (MOS-PF) decreased by 4.79 (SD=12.56, p<0.001). There was a 10% reduction in the odds of weight gain for participants who reported 300min/week or more of moderate to vigorous physical activity (MVPA) compared to less than 150min of MVPA. The proportion of MVPA that was vigorous was not associated with weight change. With the physical functioning outcome, there were independent protective effects from volume and intensity of physical activity. Independent of total MVPA, each 1% increase in the proportion of total activity that was vigorous was associated with a 0.3% decrease in the odds of decline in physical function.

CONCLUSION

These prospective findings indicate that VPA per se plays an important role in the prevention of functional decline.

Combined heart rate- and accelerometer-assessed physical activity energy expenditure and associations with glucose homeostasis markers in a population at high risk of developing diabetes: the ADDITION-PRO study

OBJECTIVE

Regular physical activity (PA) reduces the risk of developing type 2 diabetes, and different subtypes of dysglycemia have shown different associations with PA. To better understand the associations of PA and glucose homeostasis, we examined the association of objectively measured PA energy expenditure (PAEE) with detailed measures of glucose homeostasis.

RESEARCH DESIGN AND METHODS

In 1,531 men and women, with low to high risk of developing type 2 diabetes, we measured 7 days of PAEE using a combined accelerometry and heart rate monitor (ActiHeart). Measures and indices of glucose homeostasis were derived from a 3-point oral glucose tolerance test in addition to measures of long-term glycemia (glycated hemoglobin A1c and advanced glycation end products). Associations of PAEE with glucose homeostasis markers were examined using linear regression models.

RESULTS

Median age (IQR) was 66.6 years (62.1-71.6) (54% men) with a median ActiHeart wear time of 6.9 days (6.0-7.1) and PAEE level of 33.0 kJ/kg/day (23.5-46.1). In fully adjusted models, we found higher levels of PAEE to be positively associated with insulin sensitivity and negatively with insulin 2 h after glucose load (P<0.05).

CONCLUSIONS

Even in an elderly population with low levels of PA, we found higher objectively measured PAEE levels to be associated with a more beneficial glucose metabolic profile. Although our findings are cross-sectional, they indicate that even without high-intensity exercise, increasing the overall level of PAEE slightly in an entire population at risk for developing type 2 diabetes may be a realistic and worthwhile goal to reach in order to achieve beneficial effect in terms of glucose metabolism.

Physical activity and cardiovascular risk factors in Spanish children aged 11-13 years

INTRODUCTION AND OBJECTIVES

The prevalence of childhood obesity has increased in recent decades. The aim was to determine whether a 3-month intervention on daily physical activity at school could affect body weight and cardiovascular risk factors associated with childhood obesity.

METHODS

A total of 137 children (12[1] years old) volunteered to participate in an observational cross-sectional study. Children were allowed to join one of the following groups: a) sedentary group (2h/week of physical education at school); b) active group (2h/week of physical education at school plus 3h/week extra physical activity), and c) sports group (2h/week of physical education at school plus 5h/week extra physical activity). Anthropometric characteristics, blood pressure, physical condition (estimated by the Course-Navette test), and biochemical parameters related with cardiovascular risk factors were determined.

RESULTS

Body weight, body mass index, waist circumference, sum of skinfold thickness, body fat percentage, and fat mass index of children were decreased with high physical activity level, whereas body water content significantly increased with activity. Parameters related with cardiovascular risk -triglycerides, insulin, systolic blood pressure, and homeostatic model assessment index- presented lower values in the sports group. Maximal oxygen uptake and maximum heart rate (Course Navette test) progressively increased with activity. Children participating in a total of 7h/week of physical activity presented significantly lower odds ratio of having high levels of the following cardiovascular risk factors: waist circumference, fat mass index, and homeostatic model assessment index.

CONCLUSIONS

Physical activity is important for metabolic health in children. Children with higher levels of physical activity presented better anthropometric and biochemical profiles.

Leisure time and occupational physical activity in relation to obesity and insulin resistance: a population-based study from the Skaraborg Project in Sweden

The objective was to study obesity and insulin resistance in relation to leisure time physical activity (LTPA) and occupational physical activity (OPA) in a Swedish population, with particular focus on sex differences. Using a cross-sectional design, waist circumference, body mass index (BMI), glucose/insulin metabolism, blood pressure, heart rate, self-reported education, smoking, alcohol consumption, LTPA, and OPA were assessed in 1745 men and women (30-74 years) randomly chosen from 2 municipalities in southwestern Sweden. In both men and women, LTPA was inversely associated with BMI, waist circumference, and the homeostasis model assessment of insulin resistance (HOMA-IR), respectively. These associations remained statistically significant after adjustments for age, OPA, education, alcohol consumption, smoking, and study area, and also for BMI in the analyses concerning waist circumference and HOMA-IR. A statistically significant interaction term (P = .030), adjusted for multiple confounders, revealed a stronger association between LTPA and HOMA-IR in women compared with men. Occupational physical activity was positively associated with BMI (P < .001), waist circumference (P < .001), and HOMA-IR (P = .001), however, only in women. These associations remained when adjusting for multiple confounders. The sex differences were confirmed by statistically significant interaction terms between sex and OPA in association with BMI, waist circumference, and HOMA-IR, respectively. The observed sex differences regarding the strength of the association between LTPA and insulin resistance, and the positive association between OPA and obesity and insulin resistance found solely in women, warrant further investigation. Although exploration of the metabolic effects of OPA appears to be needed, thorough measurement of potential confounders is also vital to understand contextual effects.

Interaction between physical activity and sleep duration in relation to insulin resistance among non-diabetic Chinese adults

BACKGROUND

It is of a public health interest to explore the relationship between different types of physical activity, sleep duration and diabetes/insulin resistance. However, little is known about such relationship. This study examines the single and joint associations of different types of physical activity, and sleep duration on insulin resistance among non-diabetic Chinese adults.

METHODS

Data was collected from 1124 non-diabetic adults in Jiangsu Province from the China Health and Nutrition Survey (CHNS). Domestic, occupational, transportation and leisure physical activity were assessed in terms of metabolic equivalent (MET)-hours-per-week to account for both intensity and time spent. Sleep duration was categorized into three groups: ≤ 7 hours, 7-9 hours, and ≥ 9 hours. Insulin resistance was evaluated by the homeostasis model of assessment (HOMA) and defined as the highest quartile of HOMA.

RESULTS

Total physical activity was mainly composed of occupational activity (75.1%), followed orderly by domestic, transportation and leisure time activity in both men and women. Total physical activity level was strongly negatively associated with fasting insulin and HOMA (p < 0.001). Among four types of physical activity, occupational activity was significantly negatively associated with HOMA after full adjustment (p < 0.05). Transportation activity was also negatively associated with HOMA when adjusted for age and gender (p = 0.028). Moreover, the combination of low physical activity and short sleep duration was associated with the highest odds of insulin resistance (adjusted OR = 3.26, 95% CI: 1.57-6.78), compared to those with high physical activity and adequate sleep duration.

CONCLUSIONS

Physical activity, mainly occupational physical activity, was negatively associated with insulin resistance in non-diabetic Chinese population, independently of potential confounders. There was a synergic effect of low physical activity and short sleep duration on insulin resistance.

Does physical activity reduce the risk of prostate cancer? A systematic review and meta-analysis

CONTEXT

Numerous observational epidemiologic studies have evaluated the association between physical activity and prostate cancer (PCa); however, the existing results are inconsistent.

OBJECTIVE

To determine the association between physical activity and risk of PCa.

EVIDENCE ACQUISITION

A systematic search was performed using the Medline, Embase, and Web of Science databases through 15 May 2011 to identify all English-language articles that examined the effect of physical activity on the risk of PCa. This meta-analysis was conducted according to the guidelines for the meta-analysis of observational studies in epidemiology.

EVIDENCE SYNTHESIS

This meta-analysis consisted of 88,294 cases from 19 eligible cohort studies and 24 eligible case-control studies. When data from both types of studies were combined, total physical activity (TPA) was significantly associated with a decreased risk of PCa (pooled relative risk [RR]: 0.90; 95% confidence interval [CI], 0.84-0.95). The pooled RR for occupational physical activity (OPA) and recreational physical activity (RPA) were 0.81 (95% CI, 0.73-0.91) and 0.95 (95% CI, 0.89-1.00), respectively. Notably, for TPA, we observed a significant PCa risk reduction for individuals between 20 and 45 yr of age (RR: 0.93; 95% CI, 0.89-0.97) and between 45 and 65 yr of age (RR: 0.91; 95% CI, 0.86-0.97) who performed activities but not for individuals <20 yr of age or >65 yr of age.

CONCLUSIONS

There appears to be an inverse association between physical activity and PCa risk, albeit a small one. Given that increasing physical activity has numerous other health benefits, men should be encouraged to increase their physical activity in both occupational and recreational time to improve their overall health and potentially decrease their risk of PCa.

Physical activity, sedentary behaviors, and estimated insulin sensitivity and secretion in pregnant and non-pregnant women

BACKGROUND

Overweight and obesity during pregnancy raise the risk of gestational diabetes and birth complications. Lifestyle factors like physical activity may decrease these risks through beneficial effects on glucose homeostasis. Here we examined physical activity patterns and their relationships with measures of glucose homeostasis in late pregnancy compared to non-pregnant women.

METHODS

Normal weight and overweight women without diabetes (N = 108; aged 25-35 years) were studied; 35 were pregnant (in gestational weeks 28-32) and 73 were non-pregnant.Insulin sensitivity and β-cell response were estimated from an oral glucose tolerance test. Physical activity was measured during 10-days of free-living using a combined heart rate sensor and accelerometer. Total (TEE), resting (REE), and physical activity (PAEE) energy expenditure were measured using doubly-labeled water and expired gas indirect calorimetry.

RESULTS

Total activity was associated with reduced first-phase insulin response in both pregnant (Regression r2 = 0.11; Spearman r = -0.47; p = 0.007) and non-pregnant women (Regression r2 = 0.11 Spearman; r = -0.36; p = 0.002). Relative to non-pregnant women, pregnant women were estimated to have secreted 67% more insulin and had 10% lower fasting glucose than non-pregnant women. Pregnant women spent 13% more time sedentary, 71% less time in moderate-to-vigorous intensity activity, had 44% lower objectively measured total activity, and 12% lower PAEE than non-pregnant women. Correlations did not differ significantly for any comparison between physical activity subcomponents and measures of insulin sensitivity or secretion.

CONCLUSIONS

Our findings suggest that physical activity conveys similar benefits on glucose homeostasis in pregnant and non-pregnant women, despite differences in subcomponents of physical activity.

Thermogenesis and related metabolic targets in anti-diabetic therapy

Exercise, together with a low-energy diet, is the first-line treatment for type 2 diabetes type 2 diabetes . Exercise improves insulin sensitivity insulin sensitivity by increasing the number or function of muscle mitochondria mitochondria and the capacity for aerobic metabolism, all of which are low in many insulin-resistant subjects. Cannabinoid 1-receptor antagonists and β-adrenoceptor agonists improve insulin sensitivity in humans and promote fat oxidation in rodents independently of reduced food intake. Current drugs for the treatment of diabetes are not, however, noted for their ability to increase fat oxidation, although the thiazolidinediones increase the capacity for fat oxidation in skeletal muscle, whilst paradoxically increasing weight gain.There are a number of targets for anti-diabetic drugs that may improve insulin sensitivity insulin sensitivity by increasing the capacity for fat oxidation. Their mechanisms of action are linked, notably through AMP-activated protein kinase, adiponectin, and the sympathetic nervous system. If ligands for these targets have obvious acute thermogenic activity, it is often because they increase sympathetic activity. This promotes fuel mobilisation, as well as fuel oxidation. When thermogenesis thermogenesis is not obvious, researchers often argue that it has occurred by using the inappropriate device of treating animals for days or weeks until there is weight (mainly fat) loss and then expressing energy expenditure energy expenditure relative to body weight. In reality, thermogenesis may have occurred, but it is too small to detect, and this device distracts us from really appreciating why insulin sensitivity has improved. This is that by increasing fatty acid oxidation fatty acid oxidation more than fatty acid supply, drugs lower the concentrations of fatty acid metabolites that cause insulin resistance. Insulin sensitivity improves long before any anti-obesity effect can be detected.

Overestimation of physical activity level is associated with lower BMI: a cross-sectional analysis

BACKGROUND

Poor recognition of physical inactivity may be an important barrier to healthy behaviour change, but little is known about this phenomenon. We aimed to characterize a high-risk population according to the discrepancies between objective and self-rated physical activity (PA), defined as awareness.

METHODS

An exploratory cross-sectional analysis of PA awareness using baseline data collected from 365 ProActive participants between 2001 and 2003 in East Anglia, England. Self-rated PA was defined as 'active' or 'inactive' (assessed via questionnaire). Objective PA was defined according to achievement of guideline activity levels (≥30 minutes or <30 minutes spent at least moderate intensity PA, assessed by heart rate monitoring). Four awareness groups were created: 'Realistic Actives', 'Realistic Inactives', 'Overestimators' and 'Underestimators'. Logistic regression was used to assess associations between awareness group and 17 personal, social and biological correlates.

RESULTS

63.3% of participants (N = 231) were inactive according to objective measurement. Of these, 45.9% rated themselves as active ('Overestimators'). In a multiple logistic regression model adjusted for age and smoking, males (OR = 2.11, 95% CI = 1.12, 3.98), those with lower BMI (OR = 0.89, 95% CI = 0.84, 0.95), younger age at completion of full-time education (OR = 0.83, 95% CI = 0.74, 0.93) and higher general health perception (OR = 1.02 CI = 1.00, 1.04) were more likely to overestimate their PA.

CONCLUSIONS

Overestimation of PA is associated with favourable indicators of relative slimness and general health. Feedback about PA levels could help reverse misperceptions.

The effects of total energy expenditure from all levels of physical activity vs. physical activity energy expenditure from moderate-to-vigorous activity on visceral fat and insulin sensitivity in obese Type 2 diabetic women

AIMS

We examined the effects of physical activity with or without dietary restriction for 3 months on regional fat and insulin sensitivity and compared the effect of total energy expenditure from all levels of physical activity with that of physical activity energy expenditure from moderate-to-vigorous exercise in obese women with Type 2 diabetes.

METHODS

In this randomized, controlled trial, we assessed change of body weight, abdominal visceral fat area, subcutaneous fat area and insulin sensitivity, expressed as K(ITT), and monitored total energy expenditure and physical activity energy expenditure using an accelerometer during a 12-week intervention in four groups: control, diet, exercise and diet plus exercise.

RESULTS

The mean body mass index was 28.0 +/- 2.7 kg/m(2) and the mean duration of diabetes was 8 +/- 6 years. Both the diet and diet plus exercise groups showed significant body weight loss compared with the control group (P < 0.05). However, the visceral fat area was reduced only in the diet and exercise group (P = 0.017) and the subcutaneous fat area was reduced only in the diet group (P = 0.009). Mean energy intake was an independent determinant of the change in subcutaneous fat area (P = 0.020) and mean total anergy expenditure was an independent determinant of visceral fat area (P = 0.002). Insulin sensitivity K(ITT) was associated with physical activity energy expenditure (P = 0.006), energy intake (P = 0.047) and the change in fructosamine level (P = 0.016) but not with changes in body weight, subcutaneous fat area, visceral fat area or adipokine level.

CONCLUSIONS

Exercise had an additive effect to dietary restriction on visceral fat reduction. Visceral fat area was associated with total energy expenditure, but insulin sensitivity was associated with physical activity energy expenditure.

Estimating MET values using the ratio of HR for persons with paraplegia

The current compendium of physical activity (CPA) cannot be applied to persons with disabilities due to the lack of physical activity (PA) they are regularly engaged in and inaccurate MET values when applied to persons with disabilities.

PURPOSE

The purposes of this study were (a) to determine whether HR ratio during PA and resting can be used to accurately predict MET values of PA in persons with paraplegia, (b) to compare individual calibration (IC) with group calibration (GC) in error reduction, and (c) to examine prediction generalizability through a cross-validation design.

METHODS

Twenty-seven participants (aged 18-45 yr) with complete and incomplete paraplegia at T6 to L4 participated in this study. Oxygen uptake (VO2) and HR were measured simultaneously at rest and during 10 PA using indirect calorimetry and a Polar HR monitor. Predicted METs were calculated using the HR ratio for six activities by applying regression analysis by group (GC) and individuals (IC), respectively. The derived equations were then cross-validated using the four other activities, and corresponding METs were calculated. Absolute error rates (AC), paired t-test, and correlation (r) were used to determine the absolute and relative difference between observed and predicted METs.

RESULTS

The overall correlation coefficient (r) between HR ratio and observed METs was 0.77 using group regression and 0.93 +/- 0.05 using individual regression. GC (R2 = 0.59, AC = 0.07%-65.25%) was less accurate than IC (R2 = 0.90 +/- 0.10, AC = 1.64%-10.26%). Cross-validation results also showed higher correlations for IC (r = 0.90 in IC and 0.72 in GC) between observed and predicted METs.

CONCLUSIONS

HR ratio was able to accurately predict METs of persons with paraplegia. IC estimated METs more accurately than GC.

Validation of the historical adulthood physical activity questionnaire (HAPAQ) against objective measurements of physical activity

BACKGROUND

Lifetime physical activity energy expenditure (PAEE) is an important determinant of risk for many chronic diseases but remains challenging to measure. Previously reported historical physical activity (PA) questionnaires appear to be reliable, but their validity is less well established.

METHODS

We sought to design and validate an historical adulthood PA questionnaire (HAPAQ) against objective PA measurements from the same individuals. We recruited from a population-based cohort in Cambridgeshire, UK, (Medical Research Council Ely Study) in whom PA measurements, using individually calibrated heart rate monitoring, had been obtained in the past, once between 1994 and 1996 and once between 2000 and 2002. 100 individuals from this cohort attended for interview. Historical PA within the domains of home, work, transport, sport and exercise was recalled using the questionnaire by asking closed questions repeated for several discrete time periods from the age of 20 years old to their current age. The average PAEE from the 2 periods of objective measurements was compared to the self-reported data from the corresponding time periods in the questionnaire.

RESULTS

Significant correlations were observed between HAPAQ-derived and objectively measured total PAEE for both time periods (Spearman r = 0.44; P < 0.001). Similarly, self-reported time spent in vigorous PA was significantly correlated with objective measurements of vigorous PA (Spearman r = 0.40; P < 0.001).

CONCLUSIONS

HAPAQ demonstrates convergent validity for total PAEE and vigorous PA. This instrument will be useful for ranking individuals according to their past PA in studies of chronic disease aetiology, where activity may be an important underlying factor contributing to disease pathogenesis.

Regulation of adaptive behaviour during fasting by hypothalamic Foxa2

The lateral hypothalamic area is considered the classic 'feeding centre', regulating food intake, arousal and motivated behaviour through the actions of orexin and melanin-concentrating hormone (MCH). These neuropeptides are inhibited in response to feeding-related signals and are released during fasting. However, the molecular mechanisms that regulate and integrate these signals remain poorly understood. Here we show that the forkhead box transcription factor Foxa2, a downstream target of insulin signalling, regulates the expression of orexin and MCH. During fasting, Foxa2 binds to MCH and orexin promoters and stimulates their expression. In fed and in hyperinsulinemic obese mice, insulin signalling leads to nuclear exclusion of Foxa2 and reduced expression of MCH and orexin. Constitutive activation of Foxa2 in the brain (Nes-Cre/+;Foxa2T156A(flox/flox) genotype) results in increased neuronal MCH and orexin expression and increased food consumption, metabolism and insulin sensitivity. Spontaneous physical activity of these animals in the fed state is significantly increased and is similar to that in fasted mice. Conditional activation of Foxa2 through the T156A mutation expression in the brain of obese mice also resulted in improved glucose homeostasis, decreased fat and increased lean body mass. Our results demonstrate that Foxa2 can act as a metabolic sensor in neurons of the lateral hypothalamic area to integrate metabolic signals, adaptive behaviour and physiological responses.

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 sedentary time may predict insulin resistance independent of moderate- and vigorous-intensity physical activity

OBJECTIVE

To examine the prospective association between objectively measured time spent sedentary and insulin resistance and whether this association is independent of moderate- and vigorous-intensity physical activity (MVPA) and other relevant confounders.

RESEARCH DESIGN AND METHODS

This was a population-based study (Medical Research Council Ely study) in 376 middle-aged adults (166 men; 210 women) over 5.6 years of follow-up. Physical activity and sedentary time were measured objectively by individually calibrated minute-by-minute heart rate monitoring at both baseline and follow-up. Sedentary time was calculated as the heart rate observations (in minutes) below an individually predetermined threshold (flex heart rate) and expressed as a percentage of total monitored time during waking hours over 4 days. The percentage of time spent above 1.75 x resting heart rate represented MVPA. Fasting plasma insulin was used as a surrogate measure of insulin resistance.

RESULTS

Time spent sedentary at baseline was significantly and positively associated with log fasting insulin at follow-up (beta = 0.003, 95% CI 0.0006-0.006, P = 0.015) independent of baseline age, sex, fat mass, fasting insulin, smoking status, and follow-up time. After further adjustment for MVPA, this association was somewhat strengthened (beta = 0.004, 95% CI 0.0009-0.006, P = 0.009).

CONCLUSIONS

Time spent sedentary predicts higher levels of fasting insulin independent of the amount of time spent at moderate- and vigorous-intensity activity levels. This highlights the importance of reducing sedentary time in order to improve metabolic health, possibly in addition to the benefits associated with a physically active lifestyle.

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.

Physical activity in relation to total, advanced, and fatal prostate cancer

Physical activity has been inconsistently related to total prostate cancer and few studies have examined whether this association varies by disease aggressiveness. We examined physical activity in relation to total, advanced, and fatal prostate cancer in the NIH-AARP Diet and Health Study. At baseline (1995-1996), 293,902 men ages 50 to 71 years completed a questionnaire inquiring about current frequency of vigorous exercise of at least 20 min of duration, as well as frequency of exercise during adolescence (ages 15-18). We used proportional hazards regression to calculate multivariate relative risks (RR) and 95% confidence intervals (95% CI). During up to 8.2 years of follow-up, 17,872 prostate cancer cases were identified, including 1,942 advanced and 513 fatal cases. Comparing frequent (5+ times per week) versus infrequent (less than once per week) vigorous exercise, exercise at baseline was not associated with risk of total prostate cancer (RR, 1.01; 95% CI, 0.96-1.07; P(trend) = 0.78), advanced prostate cancer (RR, 1.14; 95% CI, 0.97-1.33; P(trend) = 0.25), or fatal prostate cancer (RR, 0.90; 95% CI, 0.67-1.20; P(trend) = 0.12). Increasing level of vigorous exercise during adolescence was associated with a small 3% reduction in total prostate cancer risk (frequent versus infrequent exercise during adolescence: RR, 0.97; 95% CI, 0.91-1.03; P(trend) = 0.03) but was not associated with risk of advanced prostate cancer (RR, 0.95; 95% CI, 0.78-1.14; P(trend) = 0.18) or fatal prostate cancer (RR, 0.96; 95% CI, 0.67-1.36; P(trend) = 0.99). Neither vigorous exercise at baseline nor exercise during adolescence was related to risk of total, advanced, or fatal prostate cancer in this large prospective cohort.