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Yo-Yo Dieters Don’t Necessarily Lack Willpower

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Aug. 17, 2012 — Even if the pounds you shed have crept back once again, you shouldn’t toss out your skinny jeans, new research suggests.

A study of postmenopausal women found that yo-yo dieters are just as likely to stick with a diet and/or exercise program as those whose weight hasn’t bounced around over the years.

Researchers call it “weight cycling.” You may know it as yo-yo dieting.

By either name, it’s been linked to unfavorable effects on body composition, metabolic rate, immune function, and body esteem, according to the researchers.

Sticking to the Diet

The study included 439 overweight, postmenopausal women who were not physically active. They were randomly assigned to a weight-loss diet and/or moderate-to-vigorous aerobic exercise for 45 minutes a day, five days a week. For comparison, other women didn’t change their diets or exercise habits.

At the beginning of the study, nearly 1 in 5 of the women reported they had lost at least 20 pounds three times, classifying them as “severe weight cyclers.” A quarter of the women said they’d lost at least 10 pounds three times, making them moderate weight cyclers.

Overall, the women with a history of yo-yo dieting were heavier and had less favorable metabolic and hormonal profiles than the other women. Those differences stemmed from their higher BMI, larger waistlines, and greater percentage of body fat, not weight cycling itself.

By the end of the study, the women with a history of weight cycling had fared at least as well as the other women, in terms of weight loss and improvements in their metabolic and hormonal profiles.

But did the women with a history of weight cycling keep the pounds off, or was it a case of what goes down must come up? The researchers are checking on that.

“We have been able to follow many of the women out to a couple of years,” says researcher Anne McTiernan, MD, PhD, a member of the Fred Hutchinson Cancer Center’s Public Health Sciences Division. “We’re analyzing results from that follow-up now.”

Slimming Down: The Big Picture

The study was designed to test the effects of diet and/or exercise on body weight and composition but not specifically differences related to yo-yo dieting. “That limits a little what they can say,” says Victoria Stevens, PhD, strategic director for laboratory sciences at the American Cancer Society. “Other than that, it’s a good study.”

Some studies have linked weight cycling to an increased risk of death, but few of them distinguished intentional weight loss from weight loss due to illness. Stevens recently published a study of more than 100,000 men and women who were asked how many times they had intentionally lost and regained 10 pounds or more. After accounting for BMI and other risk factors, her research did not find that weight cycling was associated with an increased risk of death.

Stevens notes that the people in her study were born around the time of World War II, when childhood obesity wasn’t as big a problem as it is now. “They just got fatter as they got older,” she says. Today, though, people start weight cycling as teenagers, and the timing could make a difference as far as risk of death, Stevens says. “I think that’s going to be a really important question to address.”

So is it worth trying yet again to slim down?

“Women should keep trying,” McTiernan says. “If nothing else, losing weight again gives you a period of time at a lower weight, which improves your health for however long you keep the weight off.”

The study appears online in the journal Metabolism.

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