Physical activity, sedentary time and gain in overall and central body fat: 7-year follow-up of the ProActive trial cohort

Heart Rate and Cardiovascular Responses to Commercial Flights: Relationships with Physical Fitness

The aim of this study was to examine the influence of physical fitness on cardiac autonomic control in passengers prior to, during and following commercial flights. Twenty-two, physically active men (36.4 ± 6.4 years) undertook assessments of physical fitness followed by recordings of 24-h heart rate (HR), heart rate variability (HRV), and blood pressure (BP) on a Control (no flight) and Experimental (flight) day. Recordings were analyzed using a two-way analysis of variance for repeated measures with relationships between variables examined via Pearson product-moment correlation coefficients. Compared to the Control day, 24-h HR was significantly greater (>7%) and HRV measures (5–39%) significantly lower on the Experimental day. During the 1-h flight, HR (24%), and BP (6%) were increased while measures of HRV (26–45%) were reduced. Absolute values of HRV during the Experimental day and relative changes in HRV measures (Control-Experimental) were significantly correlated with measures of aerobic fitness (r = 0.43 to 0.51; −0.53 to −0.52) and body composition (r = −0.63 to −0.43; 0.48–0.61). The current results demonstrated that short-term commercial flying significantly altered cardiovascular function including the reduction of parasympathetic modulations. Further, greater physical fitness and lower body fat composition were associated with greater cardiac autonomic control for passengers during flights. Enhanced physical fitness and leaner body composition may enable passengers to cope better with the cardiovascular stress and high allostatic load associated with air travel for enhanced passenger well-being.

Associations of sedentary behavior and physical activity with physical measurements and dyslipidemia in school-age children: a cross-sectional study

Background

Physical activity and sedentary behavior are common factors influencing cardiovascular health. However, how school and leisure-time activity/sedentary behavior are associated with physical fitness and blood lipid levels in primary school children in consideration of gender disparity remains unclear.

Methods

Data was obtained from a health and nutrition survey on primary school children from nine areas in China. The association between physical activities/sedentary behaviors (school and leisure-time physical activity levels, screen time, and other sedentary behaviors) and anthropometric measurements/prevalence of dyslipidemia were examined by multilevel analysis (the individual level, class level, grade level, and investigation area level) adjusted for age, energy intake and family income.

Results

A total of 770 participants (average age = 9.4 ± 1.7 years) were included. Prevalence of dyslipidemia was 10.9%. Prevalence of dyslipidemia was associated with screen time in boys [OR = 3.04, 95% CI (1.24–7.45)] and inversely associated with leisure-time physical activity in boys [OR = 2.22, 95% CI (1.08–4.56)] and school-time activity in girls [OR = 5.34, 95% CI (1.18–24.16)].

Conclusions

Physical activity—but not sedentary behavior—was significantly associated with dyslipidemia in both genders. Increasing leisure-time physical activity for boys and school-time physical activity for girls may be critical.

Sedentary time and breast cancer incidence in African American women

PURPOSE

The objective of this study was to evaluate whether time spent sitting at work or watching television was associated with breast cancer risk among African American women.

METHODS

The Black Women's Health Study (analytic cohort = 46,734) is an ongoing prospective cohort study of African American women ages 21-69 at baseline (1995). Questionnaire data were used to estimate sedentary time. Total time spent sitting at work and watching television (individually and combined) at baseline and updated through follow-up (1995-2001) and breast cancer incidence (n = 2,041 incident cases, 1995-2013) was evaluated using proportional hazards regression.

RESULTS

Higher total time spent sitting at baseline (≥10 vs. <5 h/day, HR 1.27, 95 % CI 1.06, 1.53) and updated through follow-up (≥10 vs. <5 h/day, HR 1.38, 95 % CI 1.14, 1.66) was associated with an increased breast cancer risk. Associations were stronger for hormone receptor-negative tumors (≥10 vs. <5 h/day, HR 1.70, 95 % CI 1.12, 2.55) compared to hormone receptor-positive tumors (≥10 vs. <5 h/day, HR 1.16, 95 % CI 0.88, 1.52), but tests for heterogeneity were not statistically significant (p heterogeneity = 0.31). Positive associations between total time spent sitting and breast cancer incidence did not differ by physical activity level or body composition measurements.

CONCLUSIONS

Our findings suggest that high sedentary time may increase risk for breast cancer among African American women.

Sitting time and obesity in a sample of adults from Europe and the USA

BACKGROUND

Obesity is a risk factor for many chronic diseases and the prevalence is increasing worldwide. Research suggests that sedentary behaviour (sitting) may be related to obesity.

AIM

To examine the association between sitting time and obesity, while controlling for physical activity, in a large international sample.

SUBJECTS AND METHODS

In total, 5338 adults from the UK, USA, Germany, Spain, Italy, France, Portugal, Austria and Switzerland self-reported their total daily sitting time, physical activity, age, height and weight. BMI (kg/m²), total physical activity (MET-minutes/week) and sitting time (hours/day) were derived. Participants were grouped into quartiles based on their daily sitting time (<4, 4-≤6, 6-≤8 and >8 hours/day) and logistic regression models explored the odds of being obese vs normal weight for each sitting time quartile.

RESULTS

Participants in the highest sitting time quartile (≥8 hours/day) had 62% higher odds of obesity compared to participants in the lowest quartile (<4 hours/day) after adjustment for physical activity and other confounding variables (OR = 1.62, 95% CI = 1.24-2.12, p < .01).

CONCLUSION

Sitting time is associated with obesity in adults, independent of physical activity. Future research should clarify this association using objective measures of sitting time and physical activity to further inform health guidelines.

Moderate to vigorous physical activity, not sedentary time, is associated with total and regional adiposity in a sample of UK adults at risk of type 2 diabetes

How sedentary time (ST) relates to total and regional adiposity and whether these associations are independent of moderate- to vigorous-intensity physical activity (MVPA) are of clinical and public health interest. We assessed the relationship between objectively measured MVPA, ST and ST breaks in adults at risk of type 2 diabetes. The sample consisted of 163 adults (37-75 years) recruited from primary care. Dual energy x-ray absorptiometry (iDXA, GE Corp) was used to estimate total and regional (appendages and trunk) fat mass as well as fat mass in the abdominal (android) and hip/thigh (gynoid) regions. The Actigraph GT3X was worn for 7 days (participants with  ⩾4 valid days included herein) and published cut-points were applied to 15 s epoch data to estimate mean MVPA, ST and breaks in ST. Multiple regression investigated associations between both ST and MVPA with total and regional adiposity without and with adjustment for known and potential confounders (including total lean mass) and for each other. MVPA was negatively and significantly associated with total (b  =  -62; p  =  0.002), and regional (p  <  0.05) adiposity before and after adjusting for confounders including ST. Although ST was positively and significantly associated with total (b  =  46.4; p  =  0.002) and regional adiposity (all p  ⩽  0.007), these relationships disappeared after adjustment for MVPA (p  >  0.05). Sedentary breaks were not significantly related to adiposity before or after adjustment. An age-by-MVPA interaction for total, android, gynoid and trunk fat revealed that MVPA did not remain significant when controlling for ST and other covariates in the adults over 65 years old. In this sample of adults at risk of type 2 diabetes, MVPA, and not ST, was associated with total and regional adiposity after adjustment for each other. However, in older adults at risk of T2D weight related benefits may be gained from reducing daily ST and increasing MVPA.

Prevalence of Prediabetes and Abdominal Obesity Among Healthy-Weight Adults: 18-Year Trend

PURPOSE

Trends in sedentary lifestyle may have influenced adult body composition and metabolic health among individuals at presumably healthy weights. This study examines the nationally representative prevalence of prediabetes and abdominal obesity among healthy-weight adults in 1988 through 2012.

METHODS

We analyzed the National Health and Nutrition Examination Survey (NHANES) III (1988-1994) and NHANES for the years 1999 to 2012, focusing on adults aged 20 years and older who have a body mass index (BMI) of 18.5 to 24.99 and do not have diabetes, either diagnosed or undiagnosed. We defined prediabetes using glycated hemoglobin (HbA1c) level ranges from 5.7% to 6.4%, as specified by the American Diabetes Association. Abdominal obesity was measured by waist circumference and waist-to-height ratio.

RESULTS

The prevalence of prediabetes among healthy-weight adults, aged 20 years and older and without diagnosed or undiagnosed diabetes, increased from 10.2% in 1988-1994 to 18.5% in 2012. Among individuals aged 45 years and older, the prevalence of prediabetes increased from 22.0% to 33.1%. The percentage of adults aged 20 years and older with an unhealthy waist circumference increased from 5.6% in 1988-1994 to 7.6% in 2012. The percentage of individuals with an unhealthy waist-to-height ratio increased from 27.2% in 1988-1994 to 33.7% in 2012. Adjusted models found that measures of abdominal obesity were not independent predictors of prediabetes among adults with a healthy BMI.

CONCLUSIONS

Among individuals within a healthy BMI range, the prevalence of prediabetes and abdominal obesity has substantially increased. Abdominal obesity does not appear to be the primary cause of the increase.

Associations of Sedentary Time with Fat Distribution in a High-Risk Population

PURPOSE

The effect of sedentary behavior on regional fat deposition, independent of physical activity, remains equivocal. We examined the cross-sectional associations between objectively measured sedentary time and markers of regional fat distribution (heart, liver, visceral, subcutaneous, and total body fat) in a population at a high risk of type 2 diabetes mellitus (T2DM).

METHODS

Participants were recruited from primary care to two diabetes prevention programs. Sedentary time (<25 counts per 15 s) was measured using ActiGraph GT3X accelerometers. Heart, liver, visceral, subcutaneous, and total body fat were quantified using magnetic resonance images. Fat volumes were calculated by multiplying the cross-sectional areas of the fat-containing pixels by the slice thickness. The liver fat percentage was measured using a representative region of interest created in the right lobe of the liver, avoiding the main portal veins. Linear regression models examined the association of sedentary time with markers of regional fat deposition.

RESULTS

Sixty-six participants (age, 47.9 ± 16.2 yr; male, 50.0%) were included. After adjustment for several covariates, including glycemia, whole-body fat, and moderate-to-vigorous physical activity, each 30 min of sedentary time was associated with 15.7 cm higher heart fat (P = 0.008), 1.2% higher liver fat (P = 0.026), and 183.7 cm higher visceral fat (P = 0.039).

CONCLUSIONS

This study provides new evidence suggesting that objectively measured sedentary behavior may have an independent association with heart, liver, and visceral fat in individuals at a high risk of T2DM.

Associations among sedentary and active behaviours, body fat and appetite dysregulation: investigating the myth of physical inactivity and obesity

BACKGROUND

There is considerable disagreement about the association between free-living physical activity (PA) and sedentary behaviour and obesity. Moreover studies frequently do not include measures that could mediate between PA and adiposity. The present study used a validated instrument for continuous tracking of sedentary and active behaviours as part of habitual daily living, together with measures of energy expenditure, body composition and appetite dysregulation. This cross-sectional study tested the relationship between inactivity and obesity.

METHODS

71 participants (81.7% women) aged 37.4 years (±14) with a body mass index of 29.9 kg/m² (±5.2) were continuously monitored for 6-7 days to track free-living PA (light 1.5-3 metabolic equivalents (METs), moderate 3-6 METs and vigorous >6 METs) and sedentary behaviour (<1.5 METs) with the SenseWear Armband. Additional measures included body composition, waist circumference, cardiovascular fitness, total and resting energy expenditure, and various health markers. Appetite control was assessed by validated eating behaviour questionnaires.

RESULTS

Sedentary behaviour (11.06±1.72 h/day) was positively correlated with fat mass (r=0.50, p<0.001) and waist circumference (r=-0.65, p<0.001). Moderate-to-vigorous PA was negatively associated with fat mass (r=-0.72, p<0.001) and remained significantly correlated with adiposity after controlling for sedentary behaviour. Activity energy expenditure was positively associated with the level of PA and negatively associated with fat mass. Disinhibition and binge eating behaviours were positively associated with fat mass (r=0.58 and 0.47, respectively, p<0.001).

CONCLUSIONS

This study demonstrated clear associations among objective measures of PA (and sedentary behaviour), energy expenditure, adiposity and appetite control. The data indicate strong links between physical inactivity and obesity. This relationship is likely to be bidirectional.

The mysterious case of the public health guideline that is (almost) entirely ignored: call for a research agenda on the causes of the extreme avoidance of physical activity in obesity

Physical activity and exercise guidelines for weight management call for at least 60 min of daily activity. However, these documents fail to acknowledge that almost no obese adults meet this target and that non-adherence and dropout are even higher among obese individuals than the general population. The reasons for this level of activity avoidance among obese individuals remain poorly understood, and there are no evidence-based methods for addressing the problem. Opinions among exercise scientists are polarized. Some advocate moderate intensity and long duration, whereas others call for high intensity and shorter duration. The latter approach attributes the inactivity and high dropout to limited discretionary time and the slow accrual of visible benefits. However, higher intensity has been associated with non-adherence and dropout, whereas longer duration has not. A conceptual model is then proposed, according to which obesity interacts with intensity, causing physical activity and exercise to be associated with reduced pleasure among obese individuals. We theorize that, in turn, repeated experiences of reduced pleasure lead to avoidance. On this basis, we call for a research agenda aimed at identifying the causes of activity-associated and exercise-associated displeasure in obesity and, by extension, the causes of the extreme physical inactivity among obese individuals.

The independent prospective associations of activity intensity and dietary energy density with adiposity in young adolescents

There is limited evidence on the prospective association of time spent in activity intensity (sedentary (SED), moderate (MPA) or vigorous (VPA) physical activity) and dietary intake with adiposity indicators in young people. This study aimed to assess associations between (1) baseline objectively measured activity intensity, dietary energy density (DED) and 4-year change in adiposity and (2) 4-year change in activity intensity/DED and adiposity at follow-up. We conducted cohort analyses including 367 participants (10 years at baseline, 14 years at follow-up) with valid data for objectively measured activity (Actigraph), DED (4-d food diary), anthropometry (waist circumference (WC), %body fat (%BF), fat mass index (FMI), weight status) and covariates. Linear and logistic regression models were fit, including adjustment for DED and moderate-to-vigorous physical activity. Results showed that baseline DED was associated with change in WC (β for 1kJ/g difference: 0·71; 95% CI 0·26, 1·17), particularly in boys (1·26; 95% CI 0·41, 2·16 v. girls: 0·26; 95% CI −0·34, 0·87), but not with %BF, FMI or weight status. In contrast, baseline SED, MPA or VPA were not associated with any of the outcomes. Change in DED was negatively associated with FMI (β for 1kJ/g increase: −0·86; 95% CI −1·59, −0·12) and %BF (−0·86; 95% CI −1·25, −0·11) but not WC (−0·27; 95% CI −1·02, 0·48). Change in SED, MPA and VPA did not predict adiposity at follow-up. In conclusion, activity intensity was not prospectively associated with adiposity, whereas the directions of associations with DED were inconsistent. To inform public health efforts, future studies should continue to analyse longitudinal data to further understand the independent role of different energy-balance behaviours in changes in adiposity in early adolescence.

Cross-sectional and prospective associations between moderate to vigorous physical activity and sedentary time with adiposity in children

BACKGROUND

Physical activity (PA) and sedentary time (SED) have both been suggested as potential risk factors for adiposity in children. However, there is paucity of data examining the temporal associations between these variables.

OBJECTIVE

This study aimed to analyze the cross-sectional and prospective associations between PA, SED and body composition in children.

METHODS

A total of 510 children (age at baseline 10.1±0.8, age at follow-up 11.8±0.9) from six Portuguese schools from the Oeiras Municipality participated in this study. PA and SED were measured by accelerometry and trunk fat mass (TFM) and body fat mass (BFM) were measured by dual energy X-ray absorptiometry. Fat mass index (FMI) was calculated as BFM divided by height squared. Several regression models adjusted for age, sex, maturity status, follow-up duration, baseline levels of the outcome variable and SED or moderate to vigorous PA (MVPA) were performed.

RESULTS

MVPA (min per day) was cross-sectionally inversely associated with adiposity indexes (FMI, TFM and BFM). Adiposity indexes were inversely associated with time in MVPA. In prospective analyses, MVPA was associated with a lower levels of FMI (β=-0.37, 95% confidence interval (CI): -0.49 to -0.26, P<0.001), TFM (β=-0.20, 95% CI: -0.29 to -0.10, P<0.001) and BFM (β=-0.37, 95% CI: -0.49 to -0.26, P<0.001). When the model was adjusted for age, sex, maturity status and for baseline levels of the outcome variables MVPA remained a significant predictor of lower adiposity indexes (FMI: β=-0.09, 95% CI: -0.16 to -0.01, P<0.05; TFM: β=-0.08, 95% CI: -0.15 to -0.01, P<0.05; BFM: β=-0.07, 95% CI: -0.15 to 0.00, P<0.05). Adiposity was not associated with MVPA when modeled as the exposure in prospective analyses. SED was not related with adiposity indexes, except for the relationship with FMI.

CONCLUSIONS

In cross-sectional and prospective analyses, MVPA is associated with lower adiposity independent of covariates and SED. Results suggest that promoting MVPA is important for preventing gain in adiposity in healthy children.

The surprising influence of family history to type 2 diabetes on anaerobic performance of young male élite athletes

AIMS/HYPOTHESIS

It is known that family history to type 2 diabetes induces anthropometric changes in various populations. Regular physical activity can induce adaptations in these subjects regularizing body composition and anthropometric parameters. The aim of this study is therefore to understand if family history to type 2 diabetes affects anaerobic performance in young male élite athletes.

METHODS

Forty six young male élite athletes were tested. Thirty three without family history to type 2 diabetes (FH-) and thirteen with family history to type 2 diabetes (FH+). Anthropometric parameters, body composition, physiological parameters and athletic performance were assessed.

RESULTS

Weight (p 0,0050), BMI (p 0,0019), waist circumference (p 0,0090), hips circumference (p 0,0490) and WHR (p 0,0339) were different between the two groups, showing greater values for the FH + subjects. Body composition showed lower FM and higher FFM percentages for the FH + group compared to the FH-. Anaerobic performance tests showed differences between the groups highlighting that the FH + group had higher anaerobic performance values (Wingate test for FH + 512,77 ± 107,93 W vs Wingate test for FH- 447,94 ± 56,95 W).

CONCLUSIONS/INTERPRETATION

The élite athletes with FH + showed better anaerobic performances and a higher body mass. At this stage we cannot generalise, but in a sample of athletes we tested, all who were with FH + showed both interesting and unexpected results; if confirmed, this evidence may represent a remarkable knowledge for fitness coaches and professionals who are daily dealing with track and field athletes and their performances.