The reinforcing effect of exercise in anorexia nervosa: Clinical correlates and relationship to outcome.

The purpose of the current study was to examine the relative reinforcing effect of exercise compared to a non-monetary alternative reinforcer (leisure activity), and to money, before and after weight restoration in an inpatient population with anorexia nervosa (AN). Sixty-two inpatients with AN completed a progressive ratio (PR) task to earn exercise, leisure activities, or cash at low weight and after weight restoration. Measures of pathology and motivation to exercise were completed and post-treatment discharge weights were collected. Patients worked harder for exercise at low weight than after weight restoration (df = 46, t = 5.50, p < .001). PR task performance was weakly associated with a measure of commitment to exercise (low weight: r = 0.31, weight restored: r = 0.36, p < .05), but not with other clinical measures or follow-up weights. Contrary to prior suggestions, measurement of the reinforcing value of exercise among individuals with AN via a PR task does not appear valuable in assessing clinical severity or outcome. Other, simpler, self-report measures of commitment to exercise may have greater value in assessing these outcomes.