Chronic activity-based anorexia alters food intake microstructure in a time-dependent manner in female rats

Persistently disturbed eating behavior is a well-known feature of the severe eating disorder anorexia nervosa (AN) and contributes to high relapse rates. However, the underlying changes in eating microstructure are not well understood. This study employed the widely-used activity-based anorexia (ABA) model to examine feeding microstructure during acute and chronic starvation using an automated food intake monitoring system. After a 10-day acclimatization period, female adolescent Sprague-Dawley rats were assigned to the ad libitum (AL; ad libitum food, no wheel access), activity control (AC; ad libitum food, wheel access), restricted feeding (RF; food restriction, no wheel access) or ABA (food restriction, wheel access) group. Food provision was reduced to 40% to achieve 25% body weight loss in ABA (acute phase), then adapted daily to maintain the target body weight for 2 weeks (chronic phase). Body weight, wheel-running activity and food intake were assessed daily. Food-restricted groups displayed decreased food intake and body weight throughout the experiment. Wheel-running activity significantly increased only during the chronic phase in ABA rats. The 1.5-hour feeding microstructure analysis showed phase-specific alterations with ABA rats spending most time in meals acutely. During the chronic phase, ABA rats showed the longest meal duration and time spent in meals, while eating rate failed to increase to the same extent as in RF. These findings demonstrate time-dependent alterations of food intake microstructure parameters in chronic ABA rats, indicating that the chronic model might serve as a valuable tool to investigate maladaptive eating behavior in AN.