Altered dietary preference for fat and sucrose after intestinal bypass surgery in rats.

We studied changes in dietary preference for sucrose and fat before and after intestinal bypass surgery or sham bypass surgery in Sprague-Dawley rats. During 6-d test periods before and after surgery, rats were offered both ground regular rat chow (chow) and ground chow adulterated with 20 percent fat as vegetable oil (Expt 1) or ground chow adulterated with 25 percent sucrose (Expt 2). A control group was fed only ground chow throughout (Expt 3). Before surgery in both experiments with adulterated chow, the rats preferred the fat or sucrose adulterated chow over regular chow by at least a 7:1 margin. After surgery, the bypass rats continued to prefer the adulterated diets, but by only 2.5:1 and 4:1 margins, respectively. The sham bypass rats continued their preoperative pattern of intake. Total calorie intake decreased by 25 percent to 36 percent in the bypass rats fed fat and sucrose chow. In both experiments the decrease came from decreased intake of the adulterated foods only. Bypass rats in the control group decreased food intake by only 9 percent. Sham bypass rats maintained their preoperative calorie intake and patterns of intake after surgery. Body weights of bypass rats decreased significantly compared to preoperative weights and compared to weights of the sham bypass rats. These data suggests that preference for both fat and sweet foods decreases in the initial period of rapid weight loss after bypass and this decreased preference may play a role in weight loss after bypass.