What Happens To Metabolism When You Yo-yo Diet?

If you are quick to try every fad diet that comes along, you are probably well-acquainted with yo-yo dieting. Also called weight cycling, the term "yo yo dieting" was created by Kelly D. Brownell, Ph.D., at Yale University. A yo-yo dieter is someone who experiences significant increases or decreases of body weight--usually 10 lbs. or more--multiple times as a result of low-calorie dieting, according to Women's Health Magazine. This unproductive dieting causes frustration and health problems and may permanently affect your metabolism.

Metabolism Basics

The process of converting consumed products into energy is your metabolism. Your body is constantly burning calories to repair cells, help you breathe, circulate blood and adjust hormones. Your size, age, body composition and gender affect this resting level of your metabolism. Activity also affect your metabolism--the more you move, the more energy your body needs and your metabolism revs in response. Finally, digestion accounts for about 10 percent of your metabolic burn, according to MayoClinic.com.

Short-Term Effects

When you take in calories equivalent to the number you burn, your weight evens out. Low-calorie diets deprive your body of calories, so your metabolism burns stored fat and muscle to provide you with energy. When you go on extremely low-calorie diets, your body compensates by conserving energy. In interest of self-preservation, your metabolism slows down because it does not know when it will again be fed. You end up burning fewer calories overall so that you can survive on the stored fat and lean muscle you have, according to Registered Dietitian Joanne Larsen on Ask the Dietitian. You may drop weight while on the diet, but as soon as you start to eat more calories you gain weight. This is why one-third of weight lost on diets is regained within one year and almost all is regained within three to five years, according to the American Council on Exercise.

Long-Term Effects

When you lose weight quickly on an extreme diet, you are losing lean muscle along with fat. If you do not exercise during your diet, this effect will be magnified. When you weight cycle and regain weight, you are likely regaining fat only, according to Dr. Michael Roizen and Dr. Mehmet Oz in "You, On A Diet." As a result of yo-yo dieting, you have managed to lose muscle and gain proportionally more fat. Having a higher percentage of muscle elevates your metabolism because muscle tissue burns more calories at rest than does fat. So, by yo-yo dieting and continually losing fat and muscle, but gaining back only fat--you effectively lower your metabolism for the long term.

Considerations

In a 1995 study published in Obesity Research, researchers from Wayne State University found that long-term weight cycling facilitated the development of insulin resistance and increased the risk of diabetes in rats. In June 2004, researchers from the Fred Hutchinson Cancer Research Center and the University of Washington found that women's immune functions decrease in relation to how many times they follow a low-calorie diet to repeatedly lose weight. Roizen and Oz point out that weight cycling can actually be more hazardous to your health than being steadily overweight.

Strategy

Following a sensible diet involving a modest reduction of calories and increased physical activity is the most effective way to lose weight, according to the Centers for Disease Control and Prevention. Even in this case, your metabolism compensates to protect you, according to Gary Foster, the director of the Center of Obesity Research and Education at Temple University in Philadelphia. For every 10 percent you reduce your weight, you actually slow your metabolism down by 11 to 15 percent. You can compensate for this slow-down, however, by increasing your physical activity and building muscle through resistance training.