Activity-based anorexia: A biobehavioral perspective

A biobehavioral model of activity-based anorexia is examined in terms of recent evidence. Strenuous exercise reduces the value of food reinforcement and results in decreased food intake. Reduction of food intake increases the motivational value of physical exercise. This produces an escalation in activity that further suppresses appetite. Cultural practices of diet and exercise initiate this anorexic cycle, and once started the process is resistant to change. These anorexias may be the result of natural selection favoring those organisms that became active in times of food scarcity. Proximate physiological mechanism(s) appear to involve the endogenous opiate system that mediates the relationshp between running and eating. It is argued that classification of human self-starvation should be based on environmental and/or biological conditions that control food regulation. Activity anorexia may be one instance of such a classification that could account for many instances of “an orexia nervosa”.