Assessment of energy expenditure associated with physical activities in free-living obese and nonobese adolescents

BACKGROUND: Information on activity patterns and the energy cost of activities is critically missing. OBJECTIVE: We measured the energy cost of and time devoted to various activities in obese and nonobese adolescents. DESIGN: Daily energy expenditure (DEE) and its main components were determined in 27 obese and 50 nonobese adolescents aged 12-16 y by using whole-body calorimetry with the same activity program and the heart rate-recording method in free-living conditions. RESULTS: In whole-body calorimetry, energy expenditures (EEs) during sleep and sedentary activities were 18.9% and 21.5%, respectively, higher in obese subjects than in nonobese subjects (P < 0.001), but not significantly different after adjustment for fat-free mass (FFM). EEs during walking and DEEs were significantly higher in obese than in nonobese subjects, both absolutely (71% and 33%, respectively) and after adjustment for body weight or FFM (16% and 11%, respectively). In free-living conditions, EEs associated with physical activities did not differ significantly between obese and nonobese subjects, but they were 51% lower in obese subjects after adjustment for body weight (P < 0.001). The obese adolescents spent more time in light physical activities but much less time in moderate activities and sports than did the nonobese subjects. The activity-related time equivalent corrected for sedentary EE (ARTE EE(2)) averaged 69 and 122 min/d in obese and nonobese subjects, respectively (P < 0.01). CONCLUSION: Physical activity is low in obese subjects and can be assessed satisfactorily in both obese and nonobese adolescents by using ARTE EE(2) when DEE and the basal metabolic rate are known.