Additional scientific insight on weight loss — which can reduce the risk of cancer — comes from a new study led by Dr. Anne McTiernan of Fred Hutchinson Cancer Research Center.
Yo-yo dieting — the repetitive loss and regain of body weight, also known as weight cycling — does not negatively affect metabolism or one’s ability to drop pounds in the long term, according to the study published online in the journal Metabolism.
"A history of unsuccessful weight loss should not dissuade an individual from future attempts to shed pounds or diminish the role of a healthy diet and regular physical activity in successful weight management," said McTiernan, the study’s senior author.
Two-thirds of the U.S. population is currently overweight or obese and nearly half of American women are currently dieting to lose weight. Obesity is a known risk factor for many cancers as well as heart disease and diabetes. Researchers believe a relationship between body fat and the production of certain hormones and inflammatory markers contributes to increased cancer risk.
"We know there’s an association between obesity, sedentary behavior and increased risk of certain cancers," McTiernan said. "The World Health Organization estimates that a quarter to a third of cancers could be prevented with maintenance of normal weight and keeping a physically active lifestyle."
The study was based on data from 439 overweight-to-obese, sedentary Seattle-area women, ages 50 to 75, who were randomly assigned to one of four groups: reduced-calorie diet only, exercise only (mainly brisk walking), reduced-calorie diet plus exercise and a control group that received no intervention. At the end of the yearlong study, participants on the diet-only and diet-plus-exercise arms lost an average of 10 percent of their starting weight, which was the goal of the intervention.
The analysis aimed to determine whether women with a history of moderate or severe weight cycling were at a disadvantage compared to nonweight-cyclers when it came to losing weight. Of the study participants overall, 18 percent (77 women) met the criteria for severe weight cycling (having reported losing 20 or more pounds on three or more occasions) and 24 percent (103 women) met the criteria for moderate weight cycling (having reported losing 10 or more pounds on three or more occasions).
Although severe weight cyclers were, on average, nearly 20 pounds heavier than noncyclers at the start of the study, at the end of the study the researchers found no significant differences between those who yo-yo dieted and those who didn’t with regard to the ability to successfully participate in diet and/or exercise programs.
These finding may represent a first in the scientific community. "To our knowledge, no previous studies have examined the effect of prior weight cycling on the body composition, metabolic and hormonal changes induced by a comprehensive lifestyle intervention in free-living women," the authors wrote.
The National Institutes of Health, the National Cancer Institute and the Canadian Institutes of Health funded the research. The study also included investigators at Harvard Medical School, the National Cancer Institute and the University of Washington.
Co-authors from the Hutchinson Center include McTiernan Studies’ Caitlin Mason and Ikuyo Imayama, postdoctoral research fellows; Liren Xiao, a statistical research associate; and Dr. Catherine Duggan, senior staff scientist. Also from PHS: Dr. Ching-Yun Wang and Dr. Neli Ulrich, who holds a joint appointment at German Cancer Research Center and National Center for Tumour Diseases in Heidelberg, Germany.