Weight cycling is defined by repeated attempts at weight loss followed by gain that affect body composition and metabolism. Popularly referred to as “yo-yo dieting,” or the ratchet effect of dieting, weight cycling leaves a person rebounding from their loss of weight to a possibly higher weight and body fat content than where they began.
More women than men are weight cyclers, just as more women than men go on diets. Weight cyclers can be of any race, ethnicity, or age. Researchers are finding that weight cycling is beginning at an earlier and earlier age, possibly due to the increase in childhood obesity.
Weight cyclers tend to be overweight, defined as having a body mass index (BMI) of 25.0–29.9; obese, defined as having a BMI of 30–39.9; or morbidly obese, with a BMI of 40 or above. Studies have found people with higher BMIs to be more likely to engage in repeated weight cycling.
Adolescent girls of normal weight may experience weight cycling because of cultural pressures to be thin and/or because they have a distorted body image. Actors, who may need to bulk up or slim down for a role, and athletes, who often gain weight in the off season and lose it during preseason training, are other examples of normal-weight people who may experience weight cycling. Much less research is done on normal-weight people who weight cycle than on overweight and obese people who weight cycle. Most research on normal-weight yo-yo dieters is done on adolescent girls. Many studies have found that binge eating, where an individual uncontrollably eats abnormally large amounts of food at one sitting, is fairly common among weight cyclers.
In the 1980s, obesity researchers began asking whether these failed attempts at permanent weight loss affected an individual's health or ability to lose weight in the future. Weight and weight cycling are difficult topics to research in humans because so many different physical and emotional factors affect the process of weight gain and loss. These include:
Weight cycling is a sign of repeated attempts and failures to maintain or lose weight. According to the federal Weight-Control Information Network (WIN), the reasons a person may weight cycle are often associated with four causes:
Researchers generally place weight cyclers into one of three categories:
People with binge eating disorder should seek treatment or counseling of some kind. They may also consider joining a weight-loss support group or enlisting a family member or friend that has healthy habits to assist them. Habits like keeping a food journal and checking weight regularly have been associated with weight maintenance and decreased weight fluctuations.
Nutritional and dietetic concerns related to weight cycling are the same as those related to dieting and obesity in general. A nutritionist or dietitian can help plan a healthy weight-loss program and a weight maintenance program that will reduce weight cycling and focus on healthy lifestyle changes that will result in weight loss and maintenance.
Some research shows that weight cyclers become efficient at making and storing fat. Chronic dieting has been shown to alter metabolism to favor weight regain and adipose tissue storage, especially around the abdomen. Added body weight increases the risks of diabetes, hypertension, high blood lipids, and even premature death.
A panel of experts from the National Institutes of Health stated that after a person loses weight, “one-third to two-thirds of the weight is regained within one year, and almost all is regained within five years.” Scientific reviews show that one-third to two-thirds of dieters regain more weight than was lost on their diets. There is emerging support for the idea that a person can be healthy at any size and to discourage weight loss attempts followed by weight gain in favor of supporting weight maintenance and health.
Studies have found that people who successfully maintain their weight loss and do not weight cycle are those who are prepared to make changes in their lifestyle. One study found that whether dieters lost weight using a liquid diet, a formal weight-loss program such as Weight Watchers, or a self-constructed weight-loss program, everyone who successfully kept weight off for five years or more incorporated exercise into their daily routine. They also permanently changed their eating habits to eat a lower-calorie diet. Another study found that an inability or unwillingness to make behavioral changes with regard to eating and exercise was the most common predictor for regaining weight lost during dieting.
Starting in the 1980s researchers began testing a theory called the “set point” theory of weight cycling. This theory suggested that each individual has a natural set point for weight to which the body always tries to return. To explain this, researchers have suggested that the body has feedback mechanisms that adjust the metabolic rate so that fat stores are maintained at a relatively constant level.
Doing a well-controlled weight cycling study on humans is difficult. It is unethical to manipulate the weight of volunteers the way the weight of laboratory animals is manipulated because there are clear and undisputed health risks to being overweight. Instead, researchers must depend on volunteers who self-report on their weight cycling. In addition, studies must compensate for differences in age, gender, health history, activity, and other lifestyle factors that are not an issue with laboratory animals. Some of the most tightly controlled human studies were done as inpatient studies where obese individuals were put on very low-calorie diets (less than 450 calories per day) under medical supervision to stimulate rapid weight loss. This type of extreme dieting does not necessarily reflect the way the majority of people diet in the real world. Given the variety of factors that affect human studies of weight cycling, it is not surprising that results concerning the effect of weight cycling on health are conflicting.
Several small studies done in the mid-1990s found that metabolic rate, or the rate at which a person burns calories, decreased after weight loss, supporting the set point theory. Later, more rigorously controlled studies found that after a temporary initial decrease, metabolic rate returned to pre-weight loss values. Based on these more recent findings, the National Institutes of Health takes the position that it should not be harder to lose weight when dieting after weight cycling. However, as people age they burn calories more slowly. This natural slowing of metabolism may make it appear that it becomes harder and harder to lose weight after several cycles of yo-yo dieting.
Other studies have looked at whether people who gain back the same amount of weight as they have lost have a higher percentage of body fat than they did before they weight cycled. In other words, did they lose muscle, but gain back fat? Researchers have found that people gain back muscle and fat in the same proportion that they had before they dieted, but that in some people the fat is distributed differently in their body. In these people weight cycling tended to put more fat back on the stomach and less on the thighs and buttocks. This may have health implications, as people who have more fat in the stomach area are more likely to develop type 2 (adult-onset) diabetes.
Other studies have looked at the effect of weight cycling on the development of heart disease and gallstones, and on immune system functioning. Gallstones are hard, painful masses of cholesterol and calcium that form in the gallbladder and bile ducts. Some studies have found that people who weight cycle are more likely to develop gallstones. Research continues in this area. Researchers have also found that the number of natural killer (NK) cells in the immune system tends to be lower in people who yo-yo diet. NK cells are a type of white blood cell that kill abnormal body cells (e.g., cancer cells) and cells that have been infected by viruses. The health implications of this are under review. Researchers also know that people who maintain a healthy weight have fewer cardiovascular problems than people whose weight goes up and down. However, so many factors differ between people who maintain a healthy weight and those who weight cycle that no clear conclusions can be drawn. Regardless, none of these findings should discourage overweight and obese people from trying to lose weight. The documented health risks of being overweight or obese include an increased risk of developing type 2 diabetes, heart attack, high blood pressure, fatty liver disease, arthritis, sleep apnea, and certain cancers. People attempting to lose weight should do so in a healthful and moderate manner that fits their lifestyle and preferred food choices, with support from family and friends. They should be determined to make lifelong changes to correct habits that may be leading them to gain weight.
See also Anorexia nervosa ; Body for Life diet ; Bulimia nervosa ; Cabbage soup diet ; Fad diets ; Intermittent fasting ; Jenny Craig diet ; Juice fasts ; Low-fat diet .
Bacon, Linda. Health at Every Size: The Surprising Truth about Your Weight. Rev. ed. Dallas: BenBella Books, 2010.
Montani, J. P., et al. “Weight Cycling during Growth and Beyond as a Risk Factor for Later Cardiovascular Diseases: The ‘Repeated Overshoot’ Theory.” International Journal of Obesity 30, no. S4 (2006): S58–S66.
Stevens V. L., et al. “Weight Cycling and Mortality in a Large Prospective US Study.” American Journal of Epidemiology 175, no. 8 (April 15, 2012): 785–92.
Academy of Nutrition and Dietetics, 120 South Riverside Plz., Ste. 2000, Chicago, IL, 60606-6995, (312) 899-0040, (800) 877-1600, firstname.lastname@example.org, http://www.eatright.org .
Weight-Control Information Network (WIN), 1 WIN Way, Bethesda, MD, 20892-3665, (202) 828-1025, (877) 946-4627, Fax: (202) 828-1028, win@http://win.niddk.nih.gov, http://win.niddk.nih.gov .