Sept 13, 2012 by TAMMY McKENZIE
Exercise Does Not Increase Your Motivation For Food, It Decreases It
Most people believe their appetite and motivation for food will increase with hard exercise. However if you ask most people that endure vigorous workouts, that belief does not turn out to be accurate -- at least immediately following exercise. New research shows that 45 minutes of moderate-to-vigorous exercise in the morning actually reduces a person’s motivation for food.
Doing bursts of vigorous exercise not only improves cardiovascular fitness but also the body’s ability to burn fat, even during low- or moderate-intensity workouts.
In one recent study of Scottish schoolkids, researchers found that those who did 30-second sprints interspersed with breaks for just a few minutes produced better results than youngsters exercising more moderately for 30 minutes.
After vigorous exercise, the amount of fat burned increases by over 30 percent, said Jason L. Talanian, the lead author of a study on cyclists and an exercise scientist at the University of Guelph in Ontario. Cardiovascular fitness -- the ability of the heart and lungs to supply oxygen to working muscles -- improved by 13 percent. Results were independent from any type of special dieting or food plans.
"This is specifically the reason why we see so many elite athletes with efficient cardiovascular
systems and low levels of body fat," said exercise specialist Georges Poulin. Vigorous exercise not only produces elite athletes, but it also reduces the motivation for food.
Professors James LeCheminant and Michael Larson measured the neural activity of 35 women 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.
The study, published online, ahead of print in the October issue of Medicine & Science in Sports & Exercise, measured the food motivation of 18 normal-weight women and 17 clinically obese women over two separate days.
On the first day, each woman briskly walked on a treadmill for 45 minutes and then, within the hour, had their brain waves measured. Electrodes were attached to each participant’s scalp and an EEG machine then measured their neural activity while they looked at 240 images -- 120 of plated food meals and 120 of flowers. (Flowers 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 omitted the exercise. Individuals also recorded their food consumption and physical activity on the experiment days.
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."
Interestingly, the women in the experiment did not eat more food on the exercise day to "make up" for the extra calories they burned in exercise. In fact, they ate approximately the same amount of food on the non-exercise day.
Larson said this is one of the first studies to look specifically at neurologically-determined food motivation in response to exercise and that 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."
It also doesn’t matter how fit the subjects are before. Borderline sedentary subjects and college athletes have been found to have similar increases in fitness and fat burning. Even when interval training is added on top of other exercise they are currently doing, subjects still see a significant improvement.
The study gives further credibility to vigorous exercise and that people should spend more time doing high-intensity activity than they could in a single sustained effort to maximize benefits for fitness, weight-loss and food cravings.
Tammy McKenzie is a certified personal trainer and fitness specialist with a speciality in women's fitness.