Combined food intake and exercise unmask different hormonal responses in lean and obese children

Our purpose was to investigate the effect of obesity in prepubertal children on the hormonal response to exercise performed under different conditions of nutrient availability. Prepubertal obese (age, 10.3 +/- 1.8 years; % body fat, 36.1 +/- 6.1; n = 9) and lean (age, 9.2 +/- 1.6 years; % body fat, 22.2 +/- 4.1; n = 7) children completed 2 experimental sessions in which they performed a 30 min of cycling exercise at 50% of their maximal aerobic power either 1 h (T1h) or 3 h (T3h) after a standardized breakfast. Plasma insulin-like growth factor 1 (IGF-1), IGF binding protein 1 (IGFBP-1), and IGFBP-3 levels were assessed at baseline and after exercise. Urine was collected during the sessions, and catecholamine and glucocorticoid excretions were analyzed. A significant time effect was observed for IGFBP-1; postexercise levels decreased in lean and obese children (p <= 0.001). IGF-1 and IGFBP-3 were not affected by obesity or food intake combined with exercise. In lean children, urinary excretion rates of epinephrine, norepinephrine, cortisol, and cortisone were significantly higher during the sessions than during the overnight resting period; in obese children, only epinephrine in T1h was significantly increased (p <= 0.05 for all). Our study indicates that the activity of the hypothalamic-pituitary-adrenal axis and sympathetic adrenal medullary axis was similar in lean and obese children, based on measurement under resting conditions, but response to exercise performed in postprandial conditions was altered in obese children for both axes. In addition, exercise in the postprandial state elicited a decrease in IGFBP-1 plasma levels, whereas IGF-1 and IGFBP-3 levels were not significantly altered.