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BackgroundWeight loss induced only by exercise is frequently less than expected, possibly because of compensatory changes in energy intake and/or energy expenditure. The purpose of the Examination of Mechanisms (E-MECHANIC) of Exercise-Induced Weight Compensation trial is to examine whether increased energy intake and/or reduced spontaneous activity or energy expenditure (outside of structured exercise) account for the less than expected, exercise-associated weight loss.Methods/DesignE-MECHANIC is a three-arm, 6-month randomized (1:1:1) controlled trial. The two intervention arms are exercise doses that reflect current recommendations for (1) general health (8 kcal/kg body weight per week (8 KKW), about 900 kcal/wk) and (2) weight loss (20 KKW, about 2,250 kcal/wk). The third arm, a nonexercise control group, will receive health information only. The sample will include a combined total of 198sedentary, overweight or obese (body mass index: ≥25 kg/m2 to ≤45 kg/m2) men and women ages 18 to 65 years. The exercise dose will be supervised and tightly controlled in an exercise training laboratory. The primary outcome variables are energy intake, which will be measured using doubly labeled water (adjusted for change in energy stores) and laboratory-based food intake tests, and the discrepancy between expected weight loss and observed weight loss. Secondary outcomes include changes in resting metabolic rate (adjusted for change in body mass), activity levels (excluding structured exercise) and body composition. In an effort to guide the development of future interventions, the participants will be behaviorally phenotyped and defined as those who do compensate (that is, fail to lose the amount of weight expected) or do not compensate (that is, lose the amount of weight expected or more).DiscussionIn this study, we will attempt to identify underlying mechanisms to explain why exercise elicits less weight loss than expected. This information will guide the development of interventions to increase exercise-induced weight loss and maximize weight loss retention and related health benefits.Trial registrationClinicalTrials.gov ID: NCT01264406 (registration date: 20 December 2010).

BackgroundData are sparse regarding the value of physical activity (PA) surveillance among older adults—particularly among those with mobility limitations. The objective of this study was to examine longitudinal associations between objectively measured daily PA and the incidence of cardiovascular events among older adults in the LIFE (Lifestyle Interventions and Independence for Elders) study.Methods and ResultsCardiovascular events were adjudicated based on medical records review, and cardiovascular risk factors were controlled for in the analysis. Home‐based activity data were collected by hip‐worn accelerometers at baseline and at 6, 12, and 24 months postrandomization to either a physical activity or health education intervention. LIFE study participants (n=1590; age 78.9±5.2 [SD] years; 67.2% women) at baseline had an 11% lower incidence of experiencing a subsequent cardiovascular event per 500 steps taken per day based on activity data (hazard ratio, 0.89; 95% confidence interval, 0.84–0.96; P=0.001). At baseline, every 30 minutes spent performing activities ≥500 counts per minute (hazard ratio, 0.75; confidence interval, 0.65–0.89 [P=0.001]) were also associated with a lower incidence of cardiovascular events. Throughout follow‐up (6, 12, and 24 months), both the number of steps per day (per 500 steps; hazard ratio, 0.90, confidence interval, 0.85–0.96 [P=0.001]) and duration of activity ≥500 counts per minute (per 30 minutes; hazard ratio, 0.76; confidence interval, 0.63–0.90 [P=0.002]) were significantly associated with lower cardiovascular event rates.ConclusionsObjective measurements of physical activity via accelerometry were associated with cardiovascular events among older adults with limited mobility (summary score >10 on the Short Physical Performance Battery) both using baseline and longitudinal data.Clinical Trial Registration URL: http://www.clinicaltrials.gov. Unique identifier: NCT01072500.

Objective To evaluate the extent of variability in functional responses among participants in the LIFE study, and to identify the relative contributions of intervention adherence, physical activity, and demographic and health characteristics to this variability. Design Secondary analysis of the Lifestyle Interventions and Independence for Elders (LIFE) study. Setting Multicenter U.S. institutions participating in the LIFE study. Participants A volunteer sample of 1635 sedentary men and women aged 70 to 89 years who were able to walk 400 m, but had physical limitations, defined as a score on the Short Physical Performance Battery (SPPB) of ≤9. Interventions Moderate-intensity physical activity (PA, n=818) consisting of aerobic, resistance and flexibility exercises performed both center-based (twice/wk) and in or around the home environment (3-4 times/wk) or health education (HE, n=817) consisting of weekly to monthly workshops covering relevant health information. Main Outcome Measures Physical function: gait speed over 400-m and lower extremity function (SPPB) assessed at baseline, six, twelve, and 24 months. Results Greater baseline physical function (gait speed and SPPB score) was inversely associated with Δ gait speed (regression coefficient β=−0.185, p<0.001) and ΔSPPB score (β=−0.365, p<0.001), while greater number of steps per day measured by accelerometry was positively associated with Δ gait speed (β=0.035, p<0.001) and Δ SPPB score (β=0.525, p<0.001). Other baseline factors associated with positive Δ gait speed and/or SPPB score include younger age (p<0.001), lower body mass index (p<0.001), and higher self-reported physical activity (p=0.002). Conclusions Several demographic and physical activity-related factors were associated with the extent of Δ functional outcomes among participants in the LIFE study. These factors should be considered when designing interventions for improving physical function among older adults with limited mobility.

Previous studies have linked short sleep duration, poor sleep quality, and late sleep timing with lower health-related quality of life (HRQoL) in children. However, almost all studies relied solely on selfreported sleep information and most were conducted in high income countries. To address these gaps, we studied both device-measured and self-reported sleep characteristics in relation to HRQoL in a sample of children from 12 countries that vary widely in terms of economic and human development. MethodsThe study sample included 6,626 children aged 9-11 years from Australia,