The main objective of the present study was to determine whether a structured, laboratory-based exercise task would modify the energy expenditure (EE) and the pattern of spontaneous physical activity (PA) of obese boys on the day of an exercise laboratory visit and on the following day. Fourteen 10- to 15-y-old moderately obese (36.6+/-3.3% fat) boys volunteered. They each had three laboratory visits, I wk apart. In one visit, they performed a strenuous 50-min cycling task; in another, a 30-min medium-intensity cycling task; and in another (which served as placebo), they did not exercise. PA was monitored the day before (d 1), during (d 2), and after (d 3) each laboratory visit by use of a heart rate monitor and a 12-h recall interview. EE was calculated from minute-by-minute heart rate and each child's predetermined relationship between oxygen uptake and heart rate. EE and PA were analyzed from 1300 to 1900 h each day using 15-min intervals. EE tended to decrease (p < 0.087) in the afternoon of all d 2 compared with d 1, and it increased on d 3 after the medium-intensity exercise (p < 0.0005). EE during d 2 and 3 combined, compared with d 1, decreased after the high-intensity exercise (534.2 versus 564.3 kJ/h, p < 0.05). It increased after the medium-intensity exercise (561.8 versus 526.7 kJ/h, p = 0.052) and was not affected after the placebo visit (589.4 versus 574.3 kJ/h). Time spent outdoors was consistently reduced on the day of laboratory visit compared with the day before and after the visit, regardless of the contents of intervention. In conclusion, a single laboratory visit is followed by a reduction in EE and PA on the day of intervention. However, its effect on EE the following day may be dose dependent: medium-intensity exercise induces an increase in EE, but high-intensity exercise causes a decrease in EE. One implication is that intervention by physical training should employ medium-intensity exercise to enhance the EE of obese boys.

The purpose of this study is to find out the differences in physical activity (PA), energy expenditure (EE) and energy intake (EI) under free-living conditions between Japanese prepubertal obese and nonobese boys. The subjects were 15 prepubertal obese boys (Age: 11.7Ϯ0.4 years old, Body fat: 35.2Ϯ1.6%) who do not have obese parents and siblings and 15 prepubertal nonobese boys (Age: 11.8Ϯ0.4 years old, Body fat: 18.5Ϯ0.8%). We assessed their daily PA by heart rate (HR) monitoring, pedometer step counts (PSC) and time for sedentary activities (SA). We also examined calculated EE from HR-V O 2 regression, EI and percentage of macronutrient EI. Results are as follows: Percentage of body fat had significant correlation with weight, BMI, time for SA, percentage EI of protein (positive, p<0.001), V O 2max , V O 2max per body weight, V O 2max per LBM, PSC, TEE per body weight, TEI per body weight (negative, pϽ0.001), percentage of EI of carbohydrate (negative, pϽ0.01). The values of the obese were significantly lower in total EE per body weight and in total EI per body weight. EI from dinner was significantly higher in the obese group. The values of the obese were significantly higher in percentage EI from protein and that from carbohydrate. The results of this study showed prepubertal obese boys who do no't have obese parents and siblings have low PA and spend much time for sedentary activities. Obese boys consume higher percentage energy of protein and lower percentage of carbohydrate though differences in EE and EI were found only in total EE per body weight and total EI per body weight between obese boys and nonobese boys.

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