Calorie-Restricted Diets Won’t Help You Lose Weight Long Term

April 15th, 2008

It was a comment by Oprah Winfrey that set her on the path to discovering calorie-restricted diets don’t work, writes A. Janet Tomiyama in a paper called Dieting: Does It Really Work?

Tomiyama is a Ph.D. student in social psychology at UCLA, with concentrations in health and quantitative psychology. The Oprah comment was:

“Everyone knows diets don’t work. All they do is stress you out.”

Tomiyama understood why Oprah would feel this way. Diets commonly produce early results, but the weight loss too often is short lived.

The pounds rebound right back on.

Human experience is one thing. But science is something else. The science of weight loss tells us irrefutably that calorie restriction works. It’s based on the simple principle that if you consume fewer calories than you expend, you will lose weight.

So what gives? Tomiyama wondered. Why the discrepancy?

Tomiyama was intrigued by the question, but she also realized that finding the answer was important for Americans who depend on Medicare and Medicaid. As of 2004, these plans had stopped considering obesity to be a non-illness. This opened the door for funding of obesity treatments.

But if dieting were to be included in the list of treatments, proof of its long-term effectiveness would need to be found.

Tomiyama and a team of collaborators decided to conduct a review of previous studies into dieting to determine what kind of results the diets had produced. Their review focused on studies that conducted follow-ups of dieters for at least two years. Thirty-one studies met this requirement. What they found was that most study participants lost weight initially, but the majority regained the lost weight — and fully two-thirds regained the lost weight and then some.

Given that so-called yo-yo dieting is known to harmful to health, the dieters would have been better off not dieting at all.

To make matters worse, the researcher’s found that a number of the previous diet studies were methodologically flawed. Some of the flaws, included use of self-reported data and low follow-up rates, had the effect of making the diets studied appear more effective than they actually were.

As a result of these findings, Tomiyama and her colleagues concluded that “…calorie-restricting diets are not effective, and that Medicare should not fund dieting as a treatment for obesity.”

Still intrigued by the latter half of Oprah’s quote, “All they do is stress you out,” Tomiyama has taken on stress and dieting as the topic of her Ph.D. dissertation. Her hypothesis:

Dieting might be a source of psychological stress that in turn might lead to weight gain and diet failure.

Certainly, there is no shortage of research showing that presence of stress sometimes coincides with weight gain. In a focus group of women conducted by Tomiyama, 100 per cent of the participants said that they thought dieting was stressful.

But if Tomiyama has cast a dark shadow over the concept of calorie-restricted diets, she also offers hope for people trying to lose weight. During their review, the researchers found that the study participants who exercised the most achieved the best weight loss results. Exercise is known to be a physiological stress reliever. Could there be a connection? Tomiyama intends to explore this question in future research.

In the meantime, she has come to see the results of her earlier research in a more positive light. Initially, she viewed the discovery that dieting was ineffective as a means to lose weight as negative news. But now she sees it as a positive in that it will help free women from the tyranny of dieting.

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