Resting metabolic rate in preadolescent girls at high risk of obesity

OBJECTIVE: To investigate whether children at high risk of obesity have a reduced resting metabolic rate (RMR). DESIGN: Cross-sectional study. SUBJECTS: 93 healthy girls (age: 8-12 y) were allocated to one of four groups, according to the subjects' and their parents' weight status: group 1, overweight children with both parents overweight (OB/OB2; n = 17); group 2, normal weight children with both parents overweight (N/OB2; n = 28); group 3, overweight children of discordant parents (OB/OB1; n = 21) and group 4, normal weight children with both parents normal weight (N/OB0; n = 27). MEASUREMENTS: Weight, height, fat-free mass (FFM) and fat mass (FM) by bioelectrical impedance analysis (BIA), RMR (indirect calorimetry) for the duration of 25 min. RESULTS: Controlling for disparities in body composition, age and physical maturity, significant differences were found in adjusted group means of RMR (OB/OB2 1181 kcal/d; N/OB2 1276 kcal/d; OB/OB, 1234 kcal/d; N/OB0 1199 kcal/d; P < 0.02) with the OB/OB2 girls showing the lowest energy expenditure. CONCLUSION: We found evidence that preadolescent girls at risk of obesity, are not generally predisposed to a higher body weight, because of a greater metabolic efficiency. In fact, our data show that more emphasis should be laid on defining different subgroups of both overweight and normal weight subjects in studies investigating metabolic rate.