To study differences in resting energy expenditure (REE) according to its determining factors (sex, weight, body fat mass, lean body mass) and in the oxidation of energy substrates in obese and non-obese children.
We studied 71 children (39 obese and 32 non-obese) aged from 4.1 to 13.6 years. The male/female ratio was 34/37. Energy expenditure (EE) was measured by using open circuit indirect calorimetry. The oxidation of energy substrates was calculated from oxygen consumption, carbon dioxide production, and urinary nitrogen excretion from urea. Body composition was determined by anthropometry.
REE (kcal/day), adjusted for anthropometric parameters and body composition, was higher in boys than in girls. The absolute REE was significantly higher in obese than in non-obese children (1512.82 6 234.47 vs 1172.59 6 190.20) and was higher or the same when adjusted for its determinants. Compared with the non-obese group, the obese group presented a significantly higher percentage of fat oxidation (57.15 6 10.68 vs 51.08 6 13.61, p 5 0.04), a lower percentage of carbohydrate oxidation (30.10 6 9.85 vs 36.34 6 13.61, p 5 0.03) and a lower respiratory quotient (0.79 6 0.03 vs 0.82 6 0.04, p 5 0.02). No differences were found between male and female subjects in the percentages of carbohydrate, fat, and protein oxidation.
We obtained the followings conclusions: a) When adjusted for anthropometric measurements and body composition, REE was significantly higher in boys than in girls; b) REE was higher in obese than in non-obese children, after adjustment for lean body mass; and c) Compared with the control group, obese children presented a higher percentage of fat oxidation, a lower percentage of carbohydrate oxidation, and a lower respiratory quotient.