Effect of Obesity and of Starvation on Insulin Activity

Abstract

The effect of a seven-day fast on the serum levels of insulin-like activity, of free fatty acids, and of glucose during a glucose-tolerance test was studied in three groups of severely obese subjects ; (a) five non-diabetic, (b) three subclinically diabetic, and (c) four diabetic. Before the fast the non-diabetic obese subjects showed higher levels of both types of serum insulin-like activity than were found in normal subjects, while the diabetic obese subjects showed similarly raised “ atypical ” insulin-like activity levels, but like other diabetics low “ typical ” insulin-like activity levels. After a seven-day fast the insulin-like activity levels and the glucose-tolerance curves of diabetic obese subjects became more like those of the other obese subjects ; while all obese groups then showed diabetic glucose-tolerance curves, lower fasting serum glucose, higher serum insulin-like activity levels, and higher free fatty acid levels. The percentage rise in free fatty acid after the fast tended to correspond with that in atypical insulin-like activity. Evidently fasting lessens the demand for insulin, despite its causing insulin resistance, possibly from increased fat mobilization. © 1965, British Medical Journal Publishing Group. All rights reserved.