Hypophagia following dietary obesity

Two experiments examined the hypophagia that occurs when rats are switched from a high-fat to a low-fat diet. In the first experiment, rats fed a high-fat diet for eight weeks weighed 79 g more than rats fed a low-fat diet. Removal of the high-fat diet led to reduced food intake for at least four weeks. Reducing the body weight of the rats by a 24 hour fast did not alter the time course of the hypophagia. Plasma levels of free glycerol, free fatty acids and ketones were elevated during and after feeding the high-fat diet; suggesting that feeding a high-fat diet increases fat oxidation even after the high-fat diet is withdrawn. In the second experiment, feeding rats the high-fat diet for four weeks increased body weight and body fat. Starving the rats for two days after feeding the high-fat diet did not alter subsequent hypophagia and did not alter the percentage of body fat. This pattern of results is similar to that previously seen following termination of obesity-inducing insulin treatment. The results are consistent with the idea that a persistent increase in fat oxidation is responsible for the hypophagia.