RELATIONSHIP BETWEEN PHYSICAL INACTIVITY AND ADIPOSITY IN PREPUBERTALBOYS

Objective: To study the relationship between the energy expenditure fo r activity (EEAct), the level of activity and adiposity in a group of 9-year-old boys (n = 28) with different body composition (body weight, 38 +/- 10 kg [range, 23 to 66 kg]; fat mass, 23% +/- 10% [range, 8% t o 42%]). Methods: Total energy expenditure (TEE) was measured by means of the heart-rate monitoring method. EEAct was calculated as TEE - (R EE + 0.1 TEE), where REE is the postabsorptive resting energy expendit ure and 0.1 TEE corresponds to the postprandial thermogenesis (approxi mately 10% of TEE). Results: TEE, REE, and EEAct were 9388 +/- 1859, 5 154 +/- 642, and 3295 +/- 1356 kJ/day, respectively. Daily time devote d to sedentary and nonsedentary activities averaged 290 +/- 155 minute s (range, 69 to 621) and 534 +/- 150 minutes (range, 180 to 783), resp ectively. Time spent on sedentary activities was directly proportional to fat mass percentage (r = 0.46; p < 0.05). It was the only variable , among the free-living physical-activity [EEAct, TEE/(REE + 0.1 TEE) ratio, time spent in nonsedentary and sedentary activities] variables, which remained significantly in the multiple step-down regression ana lysis final equation (r = 0.46; p < 0.05). Conclusions: The positive r elationship between adiposity and time spent on sedentary activities i n 9-year-old boys suggests the importance of the role played by muscul ar activity, at least in the maintenance of obesity in childhood. Prep ubertal children children should be encouraged to spend less time on s edentary activities to treat and prevent their obesity.