Weight loss

Actually, yo-yo diets don't screw up your metabolism

Aug. 19, 2012 at 11:42 AM ET

You lost 15 pounds! And gained it back. And lost it! And gained it back. It's been this way for years, so long that you've begun to believe that you've mucked up your metabolism, not to mention your odds of ever taking that weight off permanently. 

But take heart, yo-yo dieters: A new study suggests that your history of gaining and losing, gaining and losing, actually doesn't screw up your metabolism, nor does it wreck your chances at future weight loss attempts. The new research, recently published in the journal Metabolism, provides some hopeful news for those who've tried a series of diet fads and serious programs -- Weight Watchers, paleo, cleanses -- only to put that weight right back on. 

"Just because you didn't reach or keep to a goal before doesn't mean you won't succeed if you try again," says Anne McTiernan, a researcher at Fred Hutchinson Cancer Research Center in Seattle, whose work is primarily concerned with how diet and exercise affect a person's cancer risk. 

Up to 40 percent of people in Westernized countries like the U.S. have a tendency toward weight cycling, as it's academically termed. Previous studies have turned up mixed findings on the ways our bodies and behavior changes after repeated periods of weight loss and gain. But it's a commonly held belief that yo-yo diets increase our likelihood of gaining weight over time. Still, few studies have been able to prove this, so McTiernan set out to do so. 

The study participants (nearly 400 of them) were all overweight or obese, and all were post-menopausal women -- ranging in age from 50 to 75 years old. Of the study participants, 103 women, or 24 percent, met the criteria for moderate weight cycling -- gaining and losing about 10 pounds several times over the years -- and 77 women, or 18 percent, met the criteria for severe weight cycling -- gaining and losing about 20 pounds over the years. On average, the moderate and severe cyclers were heavier than their non-cycler counterparts. 

They were assigned to one of four groups: diet, aerobic exercise, diet and aerobic exercise, and a control group. The diet they followed was based on the diabetes prevention program diet, which is one of those "diets" that's more of a lifestyle change: Women stuck to a daily calorie goal, from about 1,200 to 2,000 depending on their starting weight, aim to reduce fat to less than 30 percent of the total number of calories they ate, and they ate more fruit, veggies and fiber. For exercise, the women aimed for 45 minutes a day, five days a week, including three sessions with a personal trainer. 

The keys to these women's weight loss, McTiernan says, were these: Write down everything you eat, every day. Eat more meals at home. Weigh yourself weekly, not daily. And don't skip meals. "I think this all comes down to accountability to yourself," she explains. "If you write down what you eat, and prepare more of your meals, you can be more accountable to yourself and know whether or not you're meeting your goals." Accountability with the Fred Hutchinson staff surely helped, too -- but you can create your own buddy system with a friend, your doctor or nurse, or a weight-loss group or program. 

At the end of the study, which lasted a full year, researchers found something that they weren't expecting: The yo-yo dieters fared just as well as the non-yo-yo dieters. There was no significant difference seen in the effect of diet or exercise, body fat percentage or lean muscle mass gained or lost. 

"I was very surprised. People who have a history of weight cycling by definition have problems with lifestyle change for weight loss because they gain the weight back again," McTiernan says. "I was surprised to find that, while many of them weighed more than the non-cyclers, they did just as well at losing weight with our lifestyle-change weight program as did women who did not have a weight cycling history."

It's not clear whether these findings would apply to, say, men, or younger women. But, McTiernan advises, it's certainly worth a shot. 

"Never give up," McTiernan urges. "You and your health deserve to keep trying. If you tried one method before (like just trying to cut back a little), maybe now you can try something more structured like a group weight loss program, or at least a structured online program."