In 158 obese children, aged from three months to 15 years, blood glucose, immunoreactive insulin, and free fatty acid levels were measured during a standard oral glucose tolerance test carried out prior to treatment. The results were analyzed for the total sample as well as for three age groups: 0–5 years, 6–10 years, and 11–15 years and compared with those of 70 normal-weight children matched for age and sex.

Glucose tolerance is normal in the obese children. It is different from the controls only two hours after glucose loading, when a slight but significant elevation is found. The glucose levels at one and two hours are significantly higher in the obese children of group III than in the younger ones.

Fasting F.F.A. levels are similar in normal and obese children, but the F.F.A. decrease following glucose absorption is significantly diminished in the obese. The F.F.A. levels of the youngest obese are significantly higher than those of the older ones.

A constant and important hyperinsulinism, fasting and postabsorptive, is demonstrated in obese children of all ages, even before five years and at the beginning of obesity. Age- and sex-related differences in insulin secretion are much more marked in the obese than in normal children. The degree of hyperinsulinemia is related to the degree of obesity, but not to its duration.

The results suggest that hyperinsulinism is associated with obesity from its onset rather than being a long-term consequence of overweight. However, the origin of hyperinsulinism in obesity and the mechanism of insulin resistance still remain obscure.

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