The role of body fat in insulin sensitivity of endurance athletes.

The purpose of the study was to assess the role of adiposity in the enhanced insulin sensitivity observed in endurance athletes (EA). An oral glucose tolerance test (75 g glucose) was administered to nine EA and to 23 sedentary subjects (SS). Two different strategies were used to investigate the problem. First, body composition indicators and Vo2max were correlated with the delta insulin and delta glucose areas measured for 180 minutes following glucose ingestion. These correlation analyses were performed for the two groups combined (n = 32). No significant correlations were observed between either fat weight or percent body fat versus delta insulin, delta glucose or delta glucose/delta insulin areas. Moreover, no significant correlation was observed between the several subcutaneous fat indicators and delta insulin, delta glucose and delta glucose/delta insulin areas. The second strategy consisted of comparing EA to SS when percent body fat difference was eliminated. This was achieved by two different methods, first by covariance analysis and second by comparing subsamples of trained and non-trained subjects paired with respect to percent body fat. These two comparisons revealed that even when adiposity was equal between the groups, a significantly greater insulin sensitivity was observed in the EA group (p less than 0.01). The present results suggest that adiposity is not the determining factor for the increased insulin sensitivity of trained subjects.