After a workout, do you feel like eating a big bowl of ice cream, or munching on an apple? Some new neuroscience studies suggest exercise affects how your brain responds to food cues, and the response may change depending on your fitness level. It could be possible that by getting in better shape, you will forget about the ice cream and reach for an apple instead.
Exercise and the brain
To learn more about how exercise affects the food reward system in the brain, researchers at California Polytechnic State University in San Luis Obispo designed an experiment to measure brain activity in a group of fit, active people after exercise.
Researchers had the participants either ride a stationary bike hard for an hour or relax for an hour before wrapping their heads in M.R.I. coils. Each participant then switched activities for another M.R.I. session. Surprisingly, their brains were much less interested in food after exercise than after rest.
After each session, participants watched a slideshow that included pictures of fruits, vegetables, whole grains, cheeseburgers, ice cream sundaes and cookies. When they rested for an hour, the food reward system—which includes parts of the brain called the insula, putamen and rolandic operculum—lit up, especially with the dessert photos. When they worked out for an hour, their food-reward systems were suppressed for all the photos
The Cal-Poly food reward study may have been flawed because the participants were in better shape than most people. Another food reward study observing overweight, sedentary people found the opposite result.
Researchers at the Institute of Psychological Sciences at the University of Leeds in the U.K. recruited 34 portly men and women for an exercise program designed to burn about 500 calories per workout five days a week. Their diets weren’t controlled during the study. After 12 weeks 20 had lost an average of 11 pounds, but 14 experienced no weight loss.
After exercise, the food-reward system in the brains of the 14 who lost no weight lit up like Christmas trees at the sight of food. The response intensified throughout the study. The food-reward systems of those who lost weight appeared indifferent to food pictures after exercise.
Whip your brain into shape
Both studies suggest that the impact of exercise on appetite may depend on who you are and what kind of exercise you do. Certain types of exercise may be more effective for some people than others. More research into the food-reward system of the brain could help optimize fitness programs on an individual level.
Could it also mean that by committing to a vigorous fitness program, you can condition your brain to the level of the fit and active Cal-Poly study participants who appeared to suppress their cravings with exercise?
There’s no downside to finding out yourself.