Eating less and exercising more seems like the best advice for losing weight, but in some cases people may respond to a strenuous workout by craving food more. In a recent study, researchers at the California Polytechnic State University in San Luis Obispo examined the activity level of the brain’s food-reward system after exercise. These regions are involved in liking, wanting and being motivated to find food. Researchers asked young, active volunteers to either sit quietly or ride a stationary bicycle for an hour. Using a functional MRI, the researchers then examined the activity of the food-reward system while the participants looked at pictures of food and non-food items. People who exercised vigorously for an hour showed less activity in the food-reward regions of the brain, indicating less interest in food. Those who sat quietly responded much more to the food cues—especially high-fat and sugary items. This seems to indicate that strenuous exercise can decrease responsiveness to food cues, which might also lessen eating after exercise. The volunteers in this study, however, were all young and healthy. Does the same effect occur with sedentary people? A second study examined just that. Overweight men and women were guided through an exercise program—five times a week, with the workouts designed to burn 500 calories each time. After 12 weeks, 59 percent of the participants lost weight, 11 pounds on average. They also showed less interest in food after exercise—as judged by the activity levels in the food-reward regions of their brains. The rest of the volunteers, however, lost much less weight, and were actually more interested in food after exercise. The overall health benefits of physical activity are well documented, so exercise is always a better choice than sitting still. When it comes to fighting obesity, though, more exercise may not be the simple solution for everyone.
The surprising relationship between exercise and hunger.