If you were to go running there’s a good chance you’ll be yearning for an apple instead of a doughnut afterwards, suggests a recent brain imaging study, and that may be because your brain is pushing you towards water.
Physical activity is one factor that can influence our appetite, possibly by its role in altering our brain signals related to hunger and pleasure. This study focused on bouts of a high-intensity activity: running.
The study was small — 15 lean men — but it may help explain how exercise relates to hunger and overall health. It was published in the American Journal of Clinical Nutrition.
In the study, the men first ran for an hour and then at a later day, 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.) Continue reading
Food magazines and advertisers know it: looking at mouthwatering images of foods often triggers the urge to eat. Blame that craving on a hormone, suggests a new study featured in yesterday’s issue of Cancer Research Update.
The study looked at a hormone that has received a lot of attention lately in obesity science circles: ghrelin. The hormone is recognized for stimulating our appetite. Ghrelin levels increase before meals and decrease afterwards. Circulating ghrelin then travels to receptors in the hypothalamus that are involved in appetite regulation.
This study collected ghrelin blood levels from 8 men every 10- or 15-minutes from before breakfast until after lunch during two sessions. Between meals, the well-fed participants looked at images of tantalizing foods during one session. A week later at the next session, the men looked at images of everyday, non-food objects, like a pair of shoes or a bike.
In the 30-minutes after the men looked at both sets of images, their ghrelin levels were higher after seeing the food images then the non-food ones.
You can see the study abstract here. The study adds to what we know about how environmental factors influence eating behaviors, an important area of research for preventing cancer and other diseases.
To see how ghrelin stimulates appetite in the brain, here’s a video related to a 2008 study related to ghrelin stimulating our appetite.