Exercise Doesn't Change Your Diet

If you take up a walking program, will you naturally change to a more healthy diet? A University of Kansas "Midwest Exercise Trial," funded by the National Institutes of Health, proved what we feared all along - no.

The study followed 131 healthy but overweight people aged 17-35 for 16 months. The exercise group was put on a regimen of treadmill walking, starting at 20 minutes a day and progressing to 45 minutes a day, at the heart rate recommended for weight loss, from 60-75% of the heart rate reserve. Both the exercise group and the control group were monitored for their eating habits in the college cafeteria for six two-week periods during the study.

The results showed what the researchers suspected all along - there was no difference between the exercise group and the control group for fat, carbohydrate, or protein intake.

Exercise Doesn't Magically Change Your Diet

"It is a popular notion that people change their eating habits and change them for the better when they exercise," said Joseph E. Donnelly, KU professor of health, sport and exercise sciences. "The general public believes that everyone reduces fat and increases carbohydrate intake automatically when exercising, but this spontaneous change to a healthy diet didn't happen."

"I think it's easier for people to believe they can eat whatever they want as long as they exercise. If we read the ads in magazines or watch television, we are being told that all we have to do to lose weight is to exercise," said Debra Sullivan, associate professor of dietetics and nutrition at the KU Medical Center in Kansas City, Kansas.

The study was published in the November, 2003 issue of the American Journal of Clinical Nutrition.

Diet Plus Exercise Needed

Other studies have shown a better chance of long term weight loss and health risk reduction through combining exercise and a reduced calorie diet. Exercise alone can help reduce risk factors for heart disease and diabetes and to build lean muscle tissue, but not enough to reduce total body fat. Those seeking to lose weight need to be mindful of their eating habits and to adopt a food plan that emphasizes healthy choices and appropriate portions.

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