September 13, 2012
With Exercise, You Won’t Work Up An Appetite For Food
April Flowers for redOrbit.com - Your Universe Online
Researchers at Brigham Young University (BYU) are challenging long held assumptions about the relationship between food and exercise. Common wisdom has assumed you could "work up an appetite" with a vigorous workout. Turns out, that might not be true.
New research, published online in October's issue of Medicine & Science in Sports & Exercise, shows that 45 minutes of moderate-to-vigorous exercise in the morning actually reduces a person's motivation for food.
Professors James LeCheminant and Michael Larson measured the neural activity of 35 women (18 normal-weight and 17 clinically obese) while they viewed food images, both following a morning of exercise and a morning without exercise. They found their attentional response to the food pictures decreased after the brisk workout.
“This study provides evidence that exercise not only affects energy output, but it also may affect how people respond to food cues,” LeCheminant said.
Day one, each woman spent 45 minutes in a brisk walk on a treadmill. Within an hour of the walk, electrodes attached to each participant's scalp measured their brain waves. An EEG machine measured their neural activity while they looked at 240 images — 120 of plated food meals and 120 of flowers (which served as a control).
The same experiment was conducted one week later on the same day of the week and at the same time of the morning, but without the exercise. Participants recorded their food consumption and physical activity on the experiment days, as well.
The 45-minute exercise bout not only produced lower brain responses to the food images, but also resulted in an increase in total physical activity that day, regardless of body mass index.
“We wanted to see if obesity influenced food motivation, but it didn´t,” LeCheminant said. “However, it was clear that the exercise bout was playing a role in their neural responses to the pictures of food.”
The women ate approximately the same amount of food on both days, the exercise did not cause them to eat more to "make up" for the extra calories burned.
This is one of the first studies to look specifically at neurologically-determined food motivation in response to exercise. Researchers still need to determine how long the diminished food motivation lasts after exercise and to what extent it persists with consistent, long-term exercise.
"The subject of food motivation and weight loss is so complex," Larson said. "There are many things that influence eating and exercise is just one element.”