To determine if differences in the GH-IGF-I axis exist between children of high and low aerobic fitness who are obese or of normal weight.
124 children (ages 8–11) divided into four groups based on BMI and VO2max (mL O2/kg fat free mass(FFM)/min): normal weight — high-fit (NH), normal weight — low-fit (NL), obese — high-fit (OH), and obese — low-fit (OL). Height, weight, skinfolds, body mass index (BMI), body fat percentage and predicted VO2max (both ml/kg/min and ml/kgFFM/min) were assessed. Resting growth hormone (GH), total insulin-like growth factor 1 (total IGF-I), free insulin-like growth factor 1(free IGF-I), and insulin were measured using morning fasting blood samples.
GH was greater in the NH group compared to the OL group only (p<0.01). No group differences existed for either total IGF-I (p=0.53) or free IGF-I (p=0.189). Insulin was greater in the OH and OL groups than the NH and NL groups (p<0.01). With groups combined (or overall), insulin and free IGF-I were related to fitness (insulin — ml/kg/min: r=−0.226, p<0.05 and ml/kgFFM/min: r= −0.212, p < 0.05; free IGF-I — ml/kg/min: r=−0.219, p<0.01 and ml/kgFFM/min: r= −0.272, p < 0.05).
Fitness may contribute to the obesity related reduction of GH that may be involved with weight gain.