When rats are given access to a running wheel and put on a restricted diet, they run excessively and decrease their food intake. This pattern is known as activity-based anorexia (ABA). Diet composition has also been linked to increased running. Low protein and high carbohydrate diets, coupled with food restriction, produce more running in rats. In the present study Occidental High- (HiS) and Low- (LoS) saccharin-consuming rats were used to study vulnerability to ABA and its dependence on diet composition. Three isocaloric diets were used. The control diet was standard rat chow combined with water and mineral oil. The second diet was low protein and high carbohydrate, and the third diet was a low protein, high fat mixture. The rats were given access to running wheels and exposed to a 1-hour restricted feeding schedule, on two consecutive days, on each of the three diets. While on the low protein, high carbohydrate diet, the rats were expected to increase their running activity and decrease their food consumption more severely when restricted in feeding. Since LoS rats tend to be more emotional and less metabolically efficient, it was expected that they would have greater running activity and sharper decreases in food consumption on all three diets. Preliminary results indicate that the low protein, high carbohydrate diet intensified ABA only in LoS rats and LoS rats reacted to food restriction with larger increases in activity on all three diets.