Ileal transposition surgery attenuates the increased efficiency of weight gain on a high-fat diet.

High-fat diets enhance weight gain in rats and humans. Ileal transposition surgery (IT) causes long-term weight loss on ad libitum food intake. This study was designed to study the effect of high-fat diets on weight loss following ileal transposition surgery. We weight matched 40 rats, performed IT or sham IT, and fed defined high-carbohydrate (12 percent kcal as fat) or high-fat (45 percent kcal as fat) diets for 15 weeks postsurgery (N = 10/group, data are means +/- s.e.m.). Overall, IT rats ate less than sham IT rats, 9587 +/- 304 v. 10,615 +/- 356 kcal (39.6 +/- 1.2 v. 43.8 +/- 1.5 MJ) (P less than 0.01), and gained less weight (-14 +/- 7.8 v. 46 +/- 13.7 g) (P less than 0.01). Sham IT rats had similar food intakes on the two diets, but body weights were increased on the high-fat diet. However, the IT rats on the high-fat diet did not gain more weight or have higher efficiency of weight gain than did the IT rats on the high-carbohydrate diet. We conclude that ileal transposition attenuates the increased efficiency of weight gain usually associated with consumption of a high-fat diet. The mechanisms of this decreased metabolic efficiency are unclear.