Effects of preoperative exposure to a high-fat versus a low-fat diet on ingestive behavior after gastric bypass surgery in rats

The consumption of high fat and sugar diets is decreased after gastric bypass surgery (GB). The mechanisms remain unclear, with tests of motivated behavior toward fat and sugar producing conflicting results in a rat model. These discrepancies may be due to differences in presurgical maintenance diets. The authors used their GB rat model to determine whether the fat content of preoperative maintenance diets affects weight loss, calorie intake, and macronutrient selection after surgery. Male Wistar rats were either low-fat diet fed (LFDF) with normal chow or high-fat diet fed (HFDF) before randomization to GB or sham surgery. In food preference test 1, the animals were offered the choice of a vegetable drink (V8) or a high-calorie liquid (Ensure), and in food preference test 2, they could choose normal chow or a solid high-fat diet. The GB groups did not differ significantly in terms of body weight loss or caloric intake. In food preference test 1, both groups responded similarly by reducing their preference for Ensure and increasing their preference for V8. In food preference test 2, the HFDF-GB rats reduced their preference for a solid high-fat diet gradually compared with the immediate reduction observed in the LFDF-GB rats. The consumption of presurgical maintenance diets with different fat contents did not affect postoperative weight loss outcomes. Both the LFDF-GB and HFDF-GB rats exhibited behaviors consistent with the possible expression of a conditioned taste aversion to a high-fat stimulus. These results suggest that for some physiologic parameters, low-fat-induced obesity models can be used for the study of changes after GB and have relevance to many obese humans who consume high-calorie but low-fat diets.