June 7, 2011

Yo-yo Dieting Healthier Than Lifelong Obesity

A new study comparing lifelong obesity with the weight fluctuations of "yo-yo" dieting suggests people are still better off trying to lose weight, despite repeated failures at maintaining the loss, than not to diet and remain obese.

"It is clear that remaining on a stable, healthy diet provides the best outcome for health and longevity," said Dr. Edward List, a scientist at Ohio University, Athens, and the study's principal investigator.

"However, obese individuals commonly weight cycle"”they have repeated intentional weight loss followed by weight regain, often called yo-yo dieting. While yo-yo dieting is thought to be harmful, there is little hard scientific evidence to support that."

To determine the long-term health effects of yo-yo dieting, List and his colleagues conducted what they call "the first controlled study of a yo-yo diet regimen used for an entire life span."

Due to the challenges of conducting a long-term controlled feeding study in humans, the scientists used mice to test whether weight fluctuations due to yo-yo dieting are as unhealthy as lifelong obesity.

Three groups of ten mice received one of three diets: high fat, low fat or a yo-yo diet, consisting of four weeks of the high-fat diet followed by four weeks of the low-fat diet.  The mice stayed on their respective diets throughout their life span.

The researchers then obtained measures of health, including body weight, body fat and blood glucose (sugar) levels.

List said the yo-yo diet resulted in large fluctuations in these health measures, decreasing during the low-fat diet and increasing to a diabetic state during the high-fat diet.   However, when health measures during the high-fat and low-fat diet regimens of the yo-yo diet group were averaged, their "average health" was improved compared with obese mice that stayed on the high-fat diet.

Compared with the mice fed the high-fat diet, mice on the yo-yo diet lived nearly 35 percent longer, List said.

"Surprisingly, the mice on the yo-yo diet had a similar life span to that of the low-fat-fed group," he added.

The findings are important, he said, in light of the growing epidemic of obesity around the world.

"The fear of negative health consequences due to weight cycling may be overemphasized," he said.

"From our study, it appears that it is better to continue to encourage weight loss regardless of the number of attempts and failures."

The results were presented Monday at The Endocrine Society's 93rd Annual Meeting in Boston.


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