Influence of dietary fat quantity and composition on glucose tolerance and insulin sensitivity in rats

The hypothesis that dietary fat can influence glucose tolerance and insulin sensitivity adversely or beneficially was tested in rats fed diets supplemented with variable amounts and types of fat. Two concentrations of fat (10% and 20% by weight) diets were prepared and given to male Wistar rats for 5 weeks. The animals supplemented with high fat (20%) diets showed significant increase in body and visceral fat weights as compared to rats fed low fat (10%) diets. Only the rats supplemented with a diet containing 20% butter oil showed impaired glucose tolerance and insulin insensitivity compared to normal rats. However, rats fed olive oil diets had relatively normal glucose tolerance and insulin sensitivity, although they increased body weight and visceral fats in parallel with rats fed butter oil diets. Fish oil conferred protection against obesity induced by olive oil or butter oil diets and also markedly reduced the impairment in glucose tolerance and insulin sensitivity induced by butter oil. In conclusion, these results suggest that diet therapy with fish oil or olive oil may be useful for treatment of patients with impaired glucose tolerance and/or type 2 diabetes. (C) 2004 Elsevier Inc. All rights reserved.