Born to Rebound?
©iStockphoto.com/Sabrina Dei Nobili
It's bad enough that your body fights you when you try to lose weight. Now there's compelling research to show that some people may be hardwired to yo-yo.
David Kessler, M.D., former U.S. Food and Drug Administration commissioner and author of The End of Overeating, and his team of researchers at the University of California at San Francisco and Yale University, looked into the biology of weight cycling. They found that the reward circuits in the brains of people Kessler calls "conditioned hypereaters" were excessively activated simply by the smell of food and stayed that way until those people finished eating whatever was on the plate in front of them.
In other words, when you have overactive neural circuitry, resisting temptation is not a question of willpower alone. "This is a biological cause of conditioned hypereating. It's the first time we can say 'It's not your fault,' " Kessler says. He estimates that 50 percent of obese people and 30 percent of overweight people are conditioned hypereaters.
Evidence shows, however, that this reaction is partially learned, and that through conditioning, you can rewire your brain. After all, the yen to yo-yo is not just physical; emotional triggers play a huge role too. A study at Brown University found that dieters who ate in response to emotions such as stress or loneliness—as opposed to external events, like overdoing it at happy hour—were more likely to regain weight.
When Darcie Schmidt of Sioux Falls, South Dakota, was in her late twenties, she lost 75 pounds and then regained 120 over two years, largely because of emotional eating, she says. In her early thirties, she stuck to a strict diet-and-exercise regimen and shed 132 pounds. "I did not eat a single chip for 18 months," she says. But the stress of a divorce, a move, and a return to school knocked her off track, and she traded her three-mile, five-day-a-week runs for bags of those verboten chips—and regained 40 pounds.
Beck sees women like Schmidt all the time, who do well for a while, only to fall off the wagon. The problem, she believes, is that they never learned the skills needed for long-term behavior change. "They haven't been taught how to motivate themselves every day," Beck says, "or how to respond to negative thoughts and recognize a mistake as a one-time thing."
A study of 200 overweight and obese people, published in the Journal of Psychosomatic Research, supports the importance of a behavior-change approach. Along with other weight-loss techniques, one group received an additional hour of therapy, in which they learned to change their behavior; the other group did an extra hour of low-intensity exercise. After a year, those in the therapy group had maintained their weight loss, while the other group's members hadn't.
While watching the numbers on the scale fluctuate wildly is a blues inducer and clothes-budget buster, there are far more compelling reasons to hold steady. For one, your metabolism might be affected—and not in the way you probably hoped.
"If you go on a very strict diet and gain the weight back quickly, you might lose a lot of muscle and regain a lot of fat," says Keith Ayoob, M.D., R.D., an associate professor at the Albert Einstein College of Medicine. "Then your metabolism operates on a slower idle, which means it's going to be harder to lose weight as time goes on."
The more times you yo-yo, the theory goes, the more fat your body gains in each rebound. Because muscle burns 10 times more calories than fat does, your metabolism eventually will slow to a crawl.
"Losing and gaining regularly takes a huge toll on your body," Ayoob says. Beyond aesthetics, such as a loss of skin elasticity, regaining weight burdens your arteries and skeletal system, and may stress the liver, which can become covered in fat.
Yo-yoing also does a number on your ticker: A study in Clinical Cardiology found that women who weight cycle five times or more during their lifetimes may be damaging their hearts in the process.
But perhaps most startling is the dangerous and lasting effect weight cycling has on the immune system. According to the first study of the long-term impacts of yo-yo dieting, women who repeatedly lost and gained weight had lower immune function, particularly lower counts of natural killer cells. "These cells are important for fending off infections and are also vital in fighting the early stages of cancer," says Cornelia Ulrich, M.D., of the Fred Hutchinson Cancer Research Center in Seattle. Low killer-cell activity is associated with higher rates of cancer. In her study of more than a hundred overweight but otherwise healthy women, those who had yo-yoed most frequently—five times or more—decreased their natural killer-cell activity by a third.
With so many drawbacks, you might wonder if you'd be better off just accepting your belly rolls. But the perils of being overweight still outweigh the risks of yo-yoing. So how do you quit the cycle for good? Despite what you read in the tabloids, it is possible. Here are our 8 tips for stopping the yo yo.