[Basal metabolism and respiratory quotient in obese children]

Childhood obesity represents an increasing dysmetabolic condition. The aim of our study was to evaluate the influence of Fat Mass (FM%) on Resting Metabolic Rate (RMR) and Respiratory Quotient (RQ) as indicator of substrate oxidation. FFM and FM were estimated by bioelectrical impedance analysis (BIA), using the Kushner equation. Resting metabolic rate was determined by open-circuit indirect calorimetry. The mean (SD) of RMR 1517.6 (236.8) was found to be different from predicted RMR 1470.6 (190) calculated using the Fleisch equations. The best predictors of RMR were weight (p = 0.000) and FFM (p = 0.000); whereas correlation between RMR and fat mass (FM%) was not significant. Therefore low RMR cannot be responsible of fat mass degree, in fact, it is not reduced in obese children. Different values of RQ were found suggesting different metabolic behaviours to oxidate substrates. These data indicate that genetics may play a significant role in the development of many types of obesity.