Glucose Metabolism in Obese Men: Abnormal Intravenous and Normal Oral Glucose Tolerance

Abstract

Summary

Previous reports from moderately obese women have demonstrated that while intravenous glucose tolerance is generally preserved, oral glucose tolerance is frequently abnormal. On the basis of such findings it has been suggested that oral glucose tolerance testing would more reliably predict or identify the truly latent diabetic obese. In an effort to reassess this proposition, we have administered oral glucose loads and intravenous glucose challenges to 11 severely obese, otherwise healthy, male subjects. Contrary to the reports in women, intravenous glucose tolerance was abnormal or borderline in 10 of 11 men in this group, whereas oral glucose tolerance was normal by three current criteria in all subjects studied. Insulin levels rose equally high in both tests and did not correlate with these discrepant results. As a lower proportion of an intravenous glucose load is directly handled by the liver, and others have reported that hepatic resistance to the action of insulin can be reversed in the presence of high insulin levels in obesity, it is suggested that intravenous administration of glucose would unmask peripheral insulin resistance in the obese male subject.