Exercise May Up Brain's Desire for Water-Rich Foods
In a small study, Men who completed a bout of high-intensity running had increased activity in a reward-related brain area when seeing fruit and vegetable images compared to images of doughnuts or other high-calorie foods. The study was published in the American Journal of Clinical Nutrition.
Physical activity is one factor that that can influence our appetite, from brain signals that relate to hunger and pleasure. This study focused on bouts of high-intensity activity: running.
In the study, 15 lean men first ran for an hour and then at a later time, they rested for an hour. For each trial, the men had easy access to water. Ten minutes after they ran or rested, researchers scanned specific areas of the men's brain as they looked at two dozen food images. In random order, they saw images of high-calorie foods -- such as brownies, ice cream, pizza and fried chicken -- and low calorie foods, including grapes, apples, lettuce and carrots. (They also saw two dozen images of non-food items.)
After the men ran and saw the fruit and vegetable images, they had greater activity in an area of the brain known as the primary taste cortex, compared to when the men rested. Activation within this brain region increases with the anticipation of foods and when consuming foods that we perceive as being pleasant, said the study's lead author Daniel Crabtree. Previous research has also shown that this region plays a role in the regulation of thirst.
When the men saw high-calorie food images after they ran, they had relatively less activity in their hippocampus, a brain region that plays a role in triggering our desire for fatty, sweet and other high-calorie foods. This response may be related to thirst and the body's need for water, the authors hypothesize.
Source: Crabtree DR, Chambers ES, Hardwick RM, Blannin AK. "The effects of high-intensity exercise on neural responses to images of food." Am J Clin Nutr. 2013 Dec 4. [Epub ahead of print].