Glucose tolerance and insulin secretion have been measured in twenty-three obese maturity-onset diabetics (twelve high-insulin secretors and eleven lowor normal-insulin secretors) on first presentation and after 10 weeks on a low-calorie diet. There was a significant improvement in glucose tolerance alone, when the results were compared with those from diabetics not on any form of treatment.
Thereafter nine of these subjects (five high-insulin secretors and four low- or normal-insulin secretors) continued on the dietary therapy alone, and eleven of the remaining fourteen subjects (six high-insulin secretors and five low- or normal-insulin secretors) continued on the low-calorie diet with the addition of fenfluramine, and their glucose tolerance and insulin secretion were measured again after a further 10 weeks. The remaining three subjects were no longer studied. The nine subjects continuing on the diet alone showed maintenance of the improvement in glucose tolerance achieved during the first 10-week period with no significant change in insulin secretion. The eleven subjects placed on fenfluramine in addition to the diet also showed maintenance of the improvement in glucose tolerance achieved during the first 10-week period with a significant decrease in insulin secretion in the six high-insulin secreting subjects and no significant change in insulin secretion in the five lowor normal-secretors.