A study of 403 college students in Ontario, Canada looked into the links between dietary restraint, body-mass index and food reinforcement. The reinforcement value of something is defined as how hard someone is willing to work, or how much they would forego to get it. Generally speaking, for example, crack cocaine is more reinforcing, say, than Brussel sprouts. Dietary restraint is the conscious restriction of either calories or certain types of 'forbidden' foods and is believed to lie behind the beginning and perpetuation of eating disorders. The study found that for lighter women the more restrained their eating was the less reinforcing snack food was. However, for heavier women the more restrained their eating was then the more reinforcing snack food was.
Goldfield, Gary S. and Lumb, Andrew - Effects of dietary restraint and body-mass index on the relative reinforcing value of snack food. Eating Disorders January-February 2009, 17(1), 46-62