Insulin secretion in human obesity: effects of prolonged fasting and refeeding.

The effects of prolonged fasting and refeeding on insulin secretion were examined in seven obese non-diabetic subjects. Plasma insulin and C-peptide concentrations were measured before and after fasting for 7 days, and after refeeding with a low caloric diet. Urine C-peptide excretion during 24 h was determined daily during the study period. Plasma insulin and C-peptide levels fell by about 50 percent during fasting and returned to the prefasting values after refeeding. During fasting the 24-h urine C-peptide excretion was markedly diminished; after 7 days it was less than 10 percent of the prefasting level; on refeeding a low caloric diet, it increased significantly although not to the initial basal values. It is concluded that in human obesity pancreatic insulin secretion is markedly diminished by prolonged fasting.