Diet versus Exercise for Weight Loss

Karen Collins, MS, RD, CDN
American Institute for Cancer Research

With excess weight a greater problem than ever, the question of whether changing eating habits or exercise is more likely to produce weight loss is vital. A new study confirms the overall research findings that dietary change specifically eating less fat produces more weight loss than changes in exercise. But it also shows that changes in one kind of behavior may help promote changes in the other, especially among women.

Many studies have compared weight loss resulting from changing diet versus increasing activity. Most often, weight loss during programs focused on dietary change produced two to three times greater weight loss than programs focused on exercise.

However, it’s long-term results that matter for our health. One analysis of many such studies showed that by one year after the end of these programs, there was no significant difference in the weight status of participants. This raises the question of whether people can maintain changes in exercise more easily than changes in eating habits. The answer, of course, almost surely depends on individual preferences as well as how unpleasant or enjoyable the attempted diet or exercise program was.

We become overweight when we consume more calories in food and drink than we burn up. To lose weight, we need to shift that balance and burn up more than we consume. We can accomplish that by consuming fewer calories, burning more, or both. Cutting calories doesn’t necessarily have to mean going on a ‘diet.’ It can just mean avoiding or limiting one or more foods high in calories from fat (such as high-fat meat, cheese, or snack foods, or too much added fat), lots of sugar (like sweets or sweetened drinks), or alcohol. Cutting calories can also be accomplished by reducing our portion sizes, or by eating smaller portions of those high-calorie foods and filling up on larger portions of low-calorie vegetables and fruits.

Objective analysis shows that cuts in calorie consumption add up faster than increases in exercise. Studies show that a combination of smaller portions and changes in what we eat can easily add up to reduce calorie consumption by 500 daily, whereas burning an extra 500 calories daily can be a daunting target.

In this new study conducted at the University of Minnesota, moderate or substantial drops in dietary fat were linked to weight loss in overweight and obese men and women, regardless of how much they changed physical activity. On average, these successful program participants decreased the number of high-fat foods they ate by five to ten servings a week. In women, even substantial increases in exercise were not enough to produce weight loss if they did not decrease fat consumption. Men, however, were able to lose weight through increased exercise alone. This might be because the men were able to burn more calories in exercise than women, or might reflect either some metabolic difference or a problem in the study’s ability to detect changes accurately.

For men, the effects of exercise and dietary fat seemed to have independent effects on the amount of weight lost. For women, although exercise alone was not a successful weight loss strategy, at each level of dietary fat reduction those who increased exercise – moderately or substantially – lost more weight than those who changed activity less.

Whether exercise changes metabolism to allow more successful weight loss, or whether its stress-reduction benefits allow more consistent progress in changing eating habits, this and other studies show that both increasing exercise and decreasing calorie consumption clearly seems the best weight-loss choice for everyone.

Reprinted with permission from the American Institute for Cancer Research


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