Energy Expenditure during Exercise Training and Changes in Body Composition

Physical activity interventions alone often do not elicit favorable changes in body composition. However, most studies have reported only mean changes in body composition across treatment groups. PURPOSE: To examine the extent to which individual-level energy expended (EE) during an exercise program is associated with changes in body mass and composition. METHODS: The sample included 666 adult participants (43% men, 32% black) from the HERITAGE Family Study. The training involved a progressive (55-75% VO2max) 20-week cycling program. The power output and duration of each training session was recorded, and the EE (kcal) was calculated for each individual. Body weight, BMI, waist and hip circumference, fat mass (FM), fat free mass (FFM), percent body fat (%BF), CT-derived visceral adipose tissue (VAT) and subcutaneous tissue (SAT) were measured pre- and post-training. Stepwise regression models were used to determine associations between absolute changes (post-pre) in body composition from EE, age, race and baseline values. RESULTS: For the total sample, EE (mean ± SD) was 18,509 ± 6,966 kcal with -0.3 ± 2.5 kg weight loss. On average, men expended more than women (23,664 ± 6,652 vs. 14,607 ± 4,056 kcal; p<0.001) and whites expended more than blacks (20,200 ± 7,126 vs. 14,938 ± 5,008 kcal; p<0.001). For the total sample, changes in FM (p<0.01) and %BF (p<0.01) were negatively associated with EE. In women, EE was positively associated with changes in FFM (p<0.02). For men, EE was negatively associated with changes in weight (p<0.01), BMI (p<0.01), FM (p<0.03), and FFM (p<0.01). Overall, the variance in changes in body composition explained by EE was low (partial r2 = 0.5-2.3%). CONCLUSIONS: The average weight loss in this study was nominal and individual level energy expended was weakly associated with changes in body composition, particularly in men.