Nutritionists at the University of Aberdeen used brain imaging to discover a new link between exercise and appetite.
Participants in the study were found to be more likely to choose healthy options such as fruit and vegetables after running fast for an hour.
It is hoped the findings will help the understanding of how exercise can be used to tackle obesity.
Dr Daniel Crabtree, from the university's Rowett Institute of Nutrition and Health, said: "The key aim of our research was to examine the brain's responses to high and low-calorie food following a period of acute exercise.
"Our focus was on a region of the brain called the insula - commonly referred to as the 'primary taste cortex'. Activation in this region is increased in the anticipation of foods, and when consuming foods that we perceive as being pleasant."
Fifteen healthy men were asked to run at speed for an hour before undergoing a brain scan while looking at pictures of different foods.
On a second occasion they were asked to rest for an hour before viewing the same pictures.
Dr Crabtree said: "Our findings showed that activation in the insula was reduced when looking at pictures of high-calorie foods such as pizzas, burgers and doughnuts, following exercise.
"When viewing low-calorie options, for example apples, strawberries, carrots and grapes, activity in this region increased.
"We also asked people to rate their hunger levels and took blood samples to analyse two hormones relating to appetite stimulation and suppression.
"After running, the volunteer's feelings of hunger were suppressed, and the appetite hormone analysis showed us that levels of the appetite-stimulating hormone were reduced whilst levels of the appetite-suppressing hormone were increased."
The findings, published in the American Journal of Clinical Nutrition, may be related to greater thirst levels after exercise and the perception of low-calorie foods having greater water content, Dr Crabtree said.
Further similar studies of overweight or obese people are needed to explore how the link between brain activity and exercise could be used to develop advice for healthy weight loss, he added.