Circadian metabolic rhythms in obese children.

Obese children display constant hyperinsulinism and, frequently, hyperphagia. In animals, lesions of the hypothalamic system affect simultaneously the circadian rhythm of insulin secretion and of food intake. In this study, circadian metabolic rhythm was examined in obese and non-obese children, by two different protocols. (1) Oral glucose tolerance tests (OGTT) were carried out at 9 a.m. and 3 p.m. on 2 consecutive days. (2) Circadian variations of plasma glucose and insulin were determined. After OGTT, in the control children there was a significant drop in the insulin/glucose ratio in the afternoon, whereas in the obese group this ratio remained high, with no significant change during the day. Differences were also observed in free fatty acid, growth hormone, and cortisol responses. The control children showed a circadian rhythm for blood glucose levels which was not present in obesity. These preliminary data suggest impairment of metabolic rhythms in obese children; they should stimulate further studies on the hypothalamic system in obesity.