INCREASED FAT OXIDATION IN PREPUBERTAL OBESE CHILDREN - A METABOLIC DEFENSE AGAINST FURTHER WEIGHT-GAIN

The purpose of this study was to measure postabsorptive fat oxidation at rest and to assess the association between fat mass and fat oxidati on rate in prepurbertal children, who were assigned to two groups: 35 obese children (weight, 44.5 +/- 9.7 kg; fat mass; 31.7 +/- 5.4%) and 37 nonobese children (weight, 30.8 +/- 6.8 kg; fat mass, 17.5 +/- 6.7% ). Postabsorptive fat oxidation expressed in absolute value was signif icantly higher in obese than in nonobese children (31.4 +/- 9.7 mg/min vs 21.9 +/- 10.2 mg/min; p<0.001) but not when adjusted for fat-free mass by analysis of covariance with fat-free mass as the covariate (28 .2 +/- 10.6 mg/min vs 24.9 +/- 10.5 mg/min). In obese children and in the total group, fat mass and fat oxidation were significantly correla ted (r = 0.65; p<0.001). The slope of the relationship indicated that for each 10 kg additional fat mass, resting fat oxidation increased by 18 gm/day. We conclude that obese prepubertal children have a higher postabsorptive rate of fat oxidation than nonobese children. This meta bolic process may favor the achievement of a new equilibrium in fat ba lance, opposing further adipose tissue gain.