The effect of synthetic very low calorie diets on the GH-IGF-1 axis in obese subjects

Abstract

IGF-1 concentrations were measured in plasma from 20 obese patients and 20 age- and sex-matched control subjects all of whom were fasting. Plasma IGF-1 concentrations were lower ( p < 0.05) in the obese individuals than in the controls. Plasma GH and insulin responses to stimulation with oral glucose were measured in 7 healthy normal weight individuals and both before and after energy restriction in 7 obese individuals. Before treatment the obese individuals were hyperinsulinaemic (fasting and integrated stimulated concentrations p < 0.05) and showed attenuation of the plasma GH response to stimulation (peak and integrated stimulated values p < 0.05 and < 0.005, respectively) following oral glucose when compared to normal weight controls. Plasma insulin levels fell (both fasting and integrated concentrations p < 0.05 and < 0.005, respectively) and stimulated plasma GH responses increased (both peak and integrated values p < 0.01 and < 0.05, respectively) in the obese individuals following 3 wk treatment with a synthetic very low energy diet. Plasma IGF-1 concentrations remained unchanged during energy restriction. These results fail to support an endocrine IGF-1 mediated feedback inhibition on the hypothalamic-pituitary axis as the cause of the attenuated release of GH in obesity.