Glucose tolerance and insulin secretion have been measured in six overweight non-diabetic subjects on first presentation and after 5 weeks of fenfluramine treatment without dietary restriction. There was a significant improvement in glucose tolerance and a marginally significant decrease in insulin secretion.
In another six overweight non-diabetic subjects, insulin secretion and glucose tolerance were measured on first presentation, after 10 weeks of low-calorie diet, and then after a further 10 weeks of the same low-calorie diet with the addition of fenfluramine. Diet alone did not produce any significant effect on glucose tolerance, but did bring about a significant decrease in insulin secretion. The addition of fenfluramine to the dietary therapy was associated with a marginally significant improvement in the glucose tolerance and a highly significant decrease in insulin secretion. This further decrease in insulin secretion was significantly greater than the decrease produced by diet alone in these six subjects.