The effects of prolonged caloric restriction leading to weight-loss on food hedonics and reinforcement.

Evidence suggests that when animals are chronically deprived of calories, the reward of a food stimulus becomes more salient. Recently leptin has been implicated in food reward. The objective of this study was to examine the effect of weight-loss on food hedonics and on the reinforcing value of palatable snack food, and to determine whether plasma leptin concentrations were related to these variables. Fifteen apparently healthy obese adults (n=9 women and 6 men; age=33.5+/-7.8; BMI=35.7+/-1.1 kg/m(2)) were subjected to 8 weeks of caloric deprivation (-700 kcal/day). Plasma leptin (ELISA), body weight and composition (Dual X-ray Absorptiometry), food reinforcement (concurrent schedules task) and food hedonics (visual analogue scale) were measured pre- and post-intervention. Body weight decreased by 5.2+/-2.7% (p=0.001) while leptin decreased by 30.1+/-32.6% (p=0.001). Relative to baseline, after weight-loss food hedonics or "liking" was rated significantly higher for the food reinforcers (p=0.001) offered at sessions end, and this change was not significantly correlated with changes in plasma leptin. No significant effect of weight-loss was noted for the reinforcing value of palatable snack food. In conclusion, after 8 weeks of caloric deprivation there was no change in the reinforcing value of palatable snack foods, but the rating of food "liking" increased ~10%, and this increase was independent of weight-loss.