RESTING ENERGY-EXPENDITURE AND FOOD-INDUCED THERMOGENESIS IN OBESE CHILDREN

Nineteen overweight girls 14.54 +/- 0.38 years of age were studied. Re sults were compared with those obtained in eight age-matched (14.07 +/ - 0.51 years) and sex-matched normal weight controls. Energy expenditu re (EE) was determined using open-circuit indirect calorimetry at rest , both after a 12-h fast and after an oral sucrose load of 3 g/kg idea l body weight. Food-induced thermogenesis (FIT) was evaluated by compu ting the area under the curve of the EE response above resting energy expenditure (REE) during the first 3 h after the sucrose load, REE (kc al/day) was higher in the overweight patients (1,818 +/- 46 vs. 1,527 +/- 67; p = 0.002); REE standardized by fat-free mass (FFM) (kcal/kg F FM/day) was lower in obese children than in controls (35.2 +/- 1.0 vs. 44.9 +/- 1.9; p = 0.0001). A linear correlation between REE and FFM w as evidenced in both controls and overweight subjects (r = 0.78 and 0. 68, respectively; p = 0.05 and p < 0.001, respectively). Actual REE in the obese children was significantly lower than the value predicted b y applying the regression equation of REE on FFM in controls to the ac tual FFM in obese children (paired t test; p = 0.003). FIT was identic al in overweight and normal weight subjects, regardless of whether it was expressed in absolute value, as the percentage calorie intake, or standardized by FFM. However, obese children were assigned to two grou ps according to whether FIT was lower than the value in controls (grou p 1, <mean - 1 SD; n = 9) or at least equal to the value in controls ( group 2, greater-than-or-equal-to mean - 1 SD, n = 10); the only featu re that discriminated between these two groups was the presence or abs ence of a family history for obesity (FHO): FIT was significantly high er in obese children with a negative FHO than in obese children with a positive FHO. Our results support the presence of an energy metabolis m disorder in some obese children and suggest that its cause may be co nstitutional in obese children with a positive FHO.