Effect of an individualized physical training program on resting cortisol and growth hormone levels and fat oxidation during exercise in obese children

Abstract

Objectives The aim of this study was to characterize the resting levels of cortisol and growth hormone (GH), and the substrate profile during exercise of obese children before and after an individualized training program. Patients and methods Twenty-two obese children (13.1 ± 0.8 yrs) were included in the study. Twelve individuals (six boys and six girls; 31.1 ± 1.1 kg/m 2, VO 2peak = 1.92 ± 0.16 l/min) participated in a two-month endurance training program and 10 individuals (five boys and five girls; 30.9 ± 1.7 kg/m 2, VO 2peak = 1.98 ± 0.12 l/min) served as controls. Training was individualized and targeting at the point were fat oxidation was maximal (Lipox max). Substrate oxidation was evaluated by indirect calorimetry. To determine plasma cortisol and GH concentrations, blood was collected at rest before and after the two-month period. Results Before the program, no significant differences were detected between the training group and the control group for any of the measured anthropometric, metabolic or hormonal variables. At the end of the two-month program, training group showed an increase in VO 2peak and fat oxidation during exercise. After the program, resting levels of GH and cortisol were significantly increased in the training group (+ 0.9 ± 0.3 ng/mL and + 55.4 ± 10.3 ng/mL respectively, p < 0.01). Following the two-month period, there was no change in any variables measured in control group. Conclusion The present data show that an individualized endurance training program targeting Lipox max improves fat oxidation during exercise and increases resting levels of GH and cortisol.