Yo-yo dieting - the repetitive loss and regain of body weight, also called weight cycling - is prevalent in the Western world, affecting an estimated 10 percent to 40 percent of the population. The degree to which weight cycling may impact metabolism or thwart a person's ability to lose weight in the long run has been unclear - until now.
A new study by researchers at Fred Hutchinson Cancer Research Center, published online in the journal Metabolism, for the first time has shown that a history of yo-yo dieting does not negatively affect metabolism or the ability to lose weight long term.
"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 the study's senior author Anne McTiernan, M.D., Ph.D., a member of the Hutchinson Center's Public Health Sciences Division.
Two-thirds of the U.S. population is currently overweight or obese and it is estimated that 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. A relationship between body fat and the production of certain hormones and inflammatory markers is thought to contribute 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.