The results of this study provide information that might be used to develop an approach to weight loss management for individuals with Prader-Willi syndrome that emphasizes the increase of output. Specifically, our finding that they do have a definite food preference and, subsequently, that they prefer a lesser amount of the high-preference food than a greater amount of low-preference food is contradictory to several non-empirical reports (Holm, 1981; Pipes & Holm, 1981). Further, the use of food as a reinforcer has been considered taboo by those who use more conventional and restrictive management approaches with Prader-Willi syndrome individuals. Our data, however, strongly suggest that a low volume of food can be used as an effective reinforcer for increased activity and exercise.