How exercise regulates your appetite

New study reveals a stomach-brain-appetite link.

by News

What foods do you usually think about at the end of a workout? Oranges and watermelon, or a big piece of cake? Recently published research in the American Journal of Clinical Nutrition gives some insight into your likely choice. 

The research group had 15 subjects run on a laboratory treadmill at a modest-but-steady pace for 60 minutes. Afterwards, the runners were placed in a functional MRI machine (fMRI) that measured their brain activity while they were being shown images of low-calorie and high-calorie foods. (If you’ve ever had a brain MRI, you’ll appreciate that this took some fancy work with mirrors to show subjects the food images.)

The team from Great Britain’s University of Birmingham hoped to detect differences they could relate to changes in stomach hormones and amino acids, specifically ghrelin and peptide YY. Previous studies had associated ghrelin and peptide YY with changes in appetite. But no prior exercise studies had mapped them to “reward centers” in the brain.

No one was surprised that the runners got hot and thirsty during their workout even though they were given as much water as they wanted. Nonetheless, they still felt thirsty after they finished the 60-minute run, and this probably influenced their reactions to the food photos: Their brain reward centers reacted more strongly to the low-calorie foods than to the high-calorie foods. This may have been because the low-calorie foods included more water-containing fruits and vegetables than the drier, denser high-calorie foods.

But the researchers also found the ghrelin and peptide YY associations they had expected in the subjects’ stomach and intestines. Running caused a decrease in ghrelin and an increase in peptide YY. High ghrelin concentrations are believed to increase appetite, while higher levels of peptide YY decrease appetite.

According to the authors, their study offers “the first direct evidence that exercise-induced changes in peripheral signals [i.e., from the stomach] related to appetite regulation and hydration status are associated with altered neural responses within brain reward regions.”

In other words, your brain and stomach are talking to each other. That has to be a good thing. And even though much has been written about your need for modest protein after a hard workout, there’s a lot to be said for fruit salad as well.

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Discuss this story

After a 60 minute run, water melon and an orange and a nice glass of skimmed milk would be my number 1 choice...after a 2 hour run, it's a nice glass of skimmed milk and half a cheesecake, the fruit salad will be picked at over the following hour.

Posted: 26/01/2014 at 19:28

After a 60 minute run, or up to maybe 15 miles at moderate pace I'd jump all over the watermelon, but if I'm racing half marathon or running 20+ miles I often get cravings for very high calorie foods such as KFC or pizza! I know you might see a connection to this and my user name, but actually a lof of the guys I run ultras with tend to agree.

I think that your body craves the water after a shorter run, but realises it needs the calories if you go harder/longer.

Posted: 27/01/2014 at 12:12

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