Does Yo-Yo Dieting Make Losing Weight More Difficult?

Myth: Yo-yo dieting ruins your metabolism and makes losing weight more difficult.

Facts: Going on and off diets does not affect your metabolism, says Nancy Snyderman, M.D., chief medical editor for NBC News.

“The human body is smarter than we are,” she says, “and is always adjusting its metabolic rate—the rate at which it burns calories.” When a person on a diet eats less, the body thinks it’s starving and drops the metabolic rate to save calories and conserve energy, says Snyderman, whose new book Diet Myths That Make Us Fat comes out in May. When dieting stops, the metabolic rate goes back up.

Robert Jeffery, director of the University of Minnesota’s Obesity Prevention Center, agrees. One’s metabolism—the amount of energy one needs each day—is a matter of muscle, he explains. All body tissue requires energy to keep going and muscle tissue requires more energy than fat tissue. The more muscle a person has, the higher the metabolic rate. As a person ages, the body tends to lose more lean muscle mass, Jeffery says, and its metabolic rate decreases as well.

Dieters, take heart: “Even if you’ve lost and regained weight countless times, don’t give up,” Snyderman writes in Diet Myths. “Yo-yo diets don’t hurt you; they just don’t get you anywhere.” The main side effect from going on and off diets is stretched skin, which tends to further frustrate the dieter, she adds.

How do you rev up your metabolism—and keep it stable? Weight training, says Jeffery, because it helps maintain muscle mass.

“The best way to keep up your metabolic rate while dieting is to throw in some exercise” so the body knows it needs to burn energy, Snyderman adds. “If we just reduce portion size and increase exercise, the weight comes off.”

Rebecca Kern is a writer based in Washington, D.C.