In one experiment, 56 adults were led on a 1.4-mile walk and were either told it would be an exercise walk or a scenic walk. The participants were given lunch after the walk, and those who were told it was an exercise outing ate 35 percent more chocolate pudding for dessert than those who were told it was a scenic walk.
In another experiment, 46 adults were given mid-afternoon snacks after their walk. Those who were told it was an exercise walk ate 124 percent more calories of candy than those who were told it was a scenic walk.
The Cornell University study was published recently in the journal Marketing Letters.
"Viewing their walk as exercise led them to be less happy and more fatigued," study author Carolina Werle, a professor at Grenoble Ecole de Management in France, said in a Cornell news release.
The findings suggest that some people in exercise programs gain weight because they reward themselves by overeating after a workout, Werle said.
The key is to make exercise enjoyable, according to study co-author Brian Wansink, director of the Cornell Food and Brand Lab.
"Do whatever you can to make your workout fun. Play music, watch a video, or simply be grateful that you're working out instead of working in the office. Anything that brings a smile is likely to get you to eat less," he said in the news release.
The U.S. National Institute of Diabetes and Digestive and Kidney Diseases offers tips to help you get active.