A new study comparing lifelong obesity with the weight fluctuations of "yo-yo dieting" suggests it is better to attempt to lose weight despite repeated failures at keeping the weight off than to not diet and remain obese. The results will be presented Monday at The Endocrine Society's 93rd Annual Meeting in Boston.
"It is clear that remaining on a stable, healthy diet provides the best outcome for health and longevity," said the study's principal investigator, Edward List, PhD, a scientist at Ohio University, Athens. "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 collaborators performed what they call "the first controlled study of a yo-yo diet regimen used for an entire life span." Because of the challenges of performing a long-term controlled feeding study in humans, they used mice to test whether weight fluctuation due to yo-yo dieting is as unhealthy as lifelong obesity.
Thirty mice, in groups of 10 each, 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. Measures of health, including body weight, body fat and blood glucose (sugar) levels, were obtained.
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. 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, he reported. Compared with the mice fed the high-fat diet, mice on the yo-yo diet lived nearly 35 percent longer.
"Surprisingly, the mice on the yo-yo diet had a similar life span to that of the low-fat-fed group," List said.
These findings are important in light of the growing epidemic of obesity around the world, he stated.
"The fear of negative health consequences due to weight cycling may be overemphasized," List concluded. "From our study, it appears that it is better to continue to encourage weight loss regardless of the number of attempts and failures."
Funding for this study came from the Ohio University Diabetes Research Initiative and the Provost's Undergraduate Research Fund, AMVETS and the National Institutes of Health.