Energy expenditure of adolescents in standardized and free-living conditions; Variations with age, gender, body composition and physical activity

Body composition (fat-free mass, FFM, and fat mass, FM), physical capacities as well as daily (DEE), sleeping (SEE) and circadian energy expenditure (EE) of 101 healthy volunteers from 10 to 28 years of age were determined by whole-body indirect calorimetry. FFM, maximal oxygen consumption (Peak VO2) and gender were the main determinants of DEE and SEE. The latter were significantly lower in females than in males, even after adjustment for FFM and Peak VO2. DEE was determined in free-living conditions over 5 days using the heart rate (HR) recording method. On a schoolday, DEE was 13 to 22% lower in girls than in boys. Two hours of physical training induced a mean 16.3% increase in DEE. Intra-group variability of DEE averaged 12.5% during a schoolday and ranged from 14 to 28% during the free days because of wide differences in physical activity.