Amygdaloid-lesion hyperphagia: impaired response to caloric challenges and altered macronutrient selection.

Lesions of the most posterodorsal aspects of the amygdala in female rats result in hyperphagia and moderate obesity. In the present study, rats with amygdaloid lesions did not increase their daily food intake when their powdered diet was diluted with 25 or 50% nonnutritive bulk. Control animals adjusted their food intake appropriately. In a second study, rats with lesions ate less food (lab chow pellets) than controls when allowed to eat for only 1 h/day for 10 days. In experiment 3, rats were offered a three-choice macronutrient diet. Whereas four of six control animals preferred the high-fat diet, all eight of the rats with amygdaloid lesions displayed a distinct preference for the high-carbohydrate diet, including those that had preferred the high-fat diet before surgery. These results, along with the previous finding that identical lesions result in hyperinsulinemia, indicate that the amygdala is involved in both the homeostatic regulation of food (caloric) intake and the selection of macronutrients.