TOTAL-ENERGY EXPENDITURE AND PATTERNS OF ACTIVITY IN 8-10-YEAR-OLD OBESE AND NONOBESE CHILDREN

Total energy expenditure (TEE) and patterns of activity were measured by means of a heart rate (HR)-monitoring method in a group of 8-10-yea r-old children including 13 obese children (weight, 46 +/- 10 kg; fat mass: 32 +/- 9%) and 16 nonobese children (weight, 31 +/- 5 kg; fat ma ss, 18 +/- 5%). Time for sleeping was not statistically different in t he two groups of children (596 +/- 33 vs. 582 +/- 43 min; p = NS). Obe se children spent more time doing sedentary activities (400 +/- 129 vs . 295 +/- 127 min; p < 0.05) and less time in nonsedentary activities (449 +/- 126 vs. 563 +/- 135 min; p < 0.05) than nonobese children. Ti me spent in moderate or vigorous activity - i.e., time spent at a HR b etween 50% of the maximal O-2 uptake (peak VO2) and 70% peak VO2 (mode rate) and at a HR greater than or equal to 70% peak VO2, (vigorous) - was not statistically different in obese and nonobese children (88 +/- 69 vs. 52 +/- 35 min and 20 +/- 21 vs. 16 +/- 13 min, respectively; p = NS). TEE was significantly higher in the obese group than in the no nobese group (9.46 +/- 1,40 vs. 7.51 +/- 1,67 MJ/day; p < 0.01). The e nergy expenditure for physical activity (plus thermogenesis) was signi ficantly higher in the obese children (3.98 +/- 1.30 vs. 2.94 +/- 1.39 MJ/day; p < 0.05). The proportion of TEE daily devoted to physical ac tivity (plus thermogenesis) was not significantly different in the two groups, as shown by the ratio between TEE and the postabsorptive meta bolic rate (PMR): 1.72 +/- 0.25 obese vs 1.61 +/- 0.28 non-obese. In c onclusion, in free-living conditions obese children have a higher TEE than do nonobese children, despite the greater time devoted to sedenta ry activities. The higher energy cost to perform weight-bearing activi ties as well as the higher absolute PMR of obese children help explain this apparent paradox.