The study, conducted at BYU (Brigham Youth University) by Professors James LeCheminant and Michael Larson, found that an exerciser's motivation for food is actually decreased after a 45 minute moderate-to-vigorous workout.
This finding supports previous research from 2011, published in Obesity Reviews, indicating that exercise may encourage people to eat healthier because of certain brain changes that affect impulsive behavior.
In the current study, thirty five women were asked to look at food pictures, both after a morning of exercise and after a morning without exercise, to make it possible for the scientists to measure their neural activity. Analysis showed, in the October issue of Medicine & Science in Sports & Exercise, that after a brisk workout, their attentional response to the images decreased.
LeCheminant explained, "This study provides evidence that exercise not only affects energy output, but it also may affect how people respond to food cues."
On two different days, the food motivation of 17 clinically obese women and 18 average-weight women was analyzed.
The subjects used a treadmill at a quick pace for 45 minutes. They had their brain waves measured within the next hour. In order to do so, electrodes were attached to each individual's scalp and an EEG machine while looking at 240 pictures: 120 of plated food meals and 120 of flowers (flowers were used as a control).
Exactly seven days later at the same time of the morning, the team performed the identical experiment, except without the workout.
On each experiment day, the women documented what they ate and their amount of physical activity.
After exercising for 45 minutes, results showed (regardless of BMI):
- a decrease in brain responses to the pictures of food
- an increase in the amount of physically activity that day
"We wanted to see if obesity influenced food motivation, but it didn't. However, it was clear that the exercise bout was playing a role in their neural responses to the pictures of food."
Surprisingly, the ladies did not consume more food on the the day of the work out to "make up" for the extra calories they shed on the treadmill. The subjects actually ate roughly the same amount of food on the non-exercise day as the one with exercise.
Further research needs to be conducted to identify how long food motivation is reduced after exercise and if it is consistent with long-term exercise, as this study is one of the first to look specifically at neurologically-determined food motivation in response to exercise.
"The subject of food motivation and weight loss is so complex," Larson added. "There are many things that influence eating and exercise is just one element."
Written by Sarah Glynn