Effects of physical training on insulin, connecting peptide (C-peptide), gastric inhibitory polypeptide (GIP) and pancreatic polypeptide (PP) levels in obese subjects.

Ten severely obese women were subjected to physical training for three months on ad libitum diet. Under metabolic ward conditions oral glucose tolerance test was performed before and after the training period with the same energy intake quantitatively and qualitatively, and glucose, insulin, connecting (C)-peptide, gastric inhibitory polypeptide (GIP) and pancreatic polypeptide (PP) were determined. In confirmation of previous work, physical training caused no decrease in body fat in these severely obese subjects, and no change in body cell mass or glucose tolerance, while insulin and blood pressure decreased. The control of dietary conditions demonstrated that the latter phenomena were not due to quantitative or qualitative changes in the diet. C-peptide concentrations decreased also, indicating effects of physical training in obesity on insulin production. GIP is believed to be a gastrointestinal factor facilitating insulin secretion (Incretin). Previous work has indicated that gastrointestinal factor(s) are involved in the insulin lowering effect seen after physical training. It is possible that GIP is contributing to this phenomenon.