Two new studies on the brain have provided a better understanding of how exercise affects our desire to eat. The first study, conducted by researchers at California Polytechnic State University, looked at how exercise affected what is called the ‘food-reward system’ region of the brain, in 30 physically-fit young adults.  They looked at the participants’ responses to photos of different foods in these areas of the brain by using magnetic resonance imaging (MRI), after resting for an hour, as well as after an intense hour-long work-out.  The researchers found that the food-reward system regularly lit up in the participants after they had rested, especially when they saw high fat or sugary images, like cheeseburgers and ice cream.   However, after exercising, the same participants’ brain scans displayed much less response to the food images.  Areas of the food-reward-system remained fairly calm, even when viewing burgers and ice cream. Questionnaires completed by the participants confirmed the findings, as they indicated that they felt less interested in food after exercising than after resting.

The second study seems to contradict the findings of the first study, but since the participants in the first study were all physically fit and in their 20’s, it may be that older, less active people respond differently to exercise when it comes to appetite and food motivation. The second study was of 34 overweight adults, who took part in a supervised exercise routine. The participants were not put on any diet restrictions and advised to eat how they liked. After 12 weeks on the program, 20 of the participants had shed a significant amount of weight, but the other 14 had shed only one or two pounds, if any. These 14 people had the highest brain responses to food cues following exercise when the study began and actually showed more enthusiasm for food after exercising at 12 weeks than at the beginning of the study. The findings suggest that in order for exercise to noticeably decrease appetite, it may be important to exercise for an hour or more and it may help to be already lean and in shape.  Exercising can have psychological effects for everyone, however, and even if it does not dampen desire for food, it might inspire better food choices, ultimately leading to weight loss.