Teens: Should You Go On a Diet?

by Food and Drug Administration (FDA)

What do the hula hoop, "high-protein diets," and wearing your clothes backwards have in common? They are all fads. Fads come and go, but when it comes to fad diets, the health effects can be permanent — especially for teenagers.

Not all teens who go on diets need to lose weight. Pressure from friends — and sometimes parents — to be very slim may create a distorted body image. Having a distorted body image is like looking into a funhouse mirror: You see yourself as fatter than you are.

A national survey of 11,631 high school students conducted by the national Centers for Disease Control and Prevention found that more than a third of the girls considered themselves overweight, compared with fewer than 15 percent of the boys. More than 43 percent of the girls reported that they were on a diet — and a quarter of these dieters didn't think they were overweight. The survey found that the most common dieting methods used were skipping meals, taking diet pills, and inducing vomiting after eating.

"The teenage years are a period of rapid growth and development," points out Ronald Kleinman, M.D., chief of the Pediatric Gastrointestinal and Nutrition Unit of Massachusetts General Hospital in Boston. He explains that fad dieting can keep teenagers from getting the calories and nutrients they need to grow properly and that dieting can retard growth. Stringent dieting may cause girls to stop menstruating, and will prevent boys from developing muscles, he says. If the diet doesn't provide enough calcium, phosphorus and vitamin D, bones may not lay down enough calcium. This may increase the risk of osteoporosis later in life, although more studies are needed to confirm this.

Instead of dieting because "everyone" is doing it or because you are not as thin as you want to be, first find out from a doctor or nutritionist whether you are carrying too much body fat for your age and height.

What if You Need to Lose Weight?

The flip side to feeling pressured to be thin is having legitimate concerns about overweight that adults dismiss by saying, "It's just baby fat" or "You'll grow into your weight." Most girls reach almost their full height once they start to menstruate, notes Kleinman. Although boys usually don't stop growing until age 18, data from a study suggest that adolescent obesity cane carry serious lifelong health consequences for them.

The study, which followed the medical histories of 508 people from childhood to age 70, found that men who had been overweight teenagers were more likely to develop colon cancer and to suffer fatal heart attacks and strokes than their thinner classmates. Women who had been overweight teens had an increased tendency to develop clogged arteries (atherosclerosis) and arthritis. By age 70, these problems made it difficult for them to walk more than a quarter mile, lift heavy objects, or climb stairs.

While this study linked adolescent obesity to health problems decades down the road, some adverse effects show up much earlier. Sometimes teens develop high blood pressure, elevated cholesterol, and conditions that often precede diabetes. Also, as Kleinman points out, "The longer in adolescence you remain overweight, the greater the likelihood that the problem will persist into adulthood."

As with most everything else, there's a right way and a wrong way to lose weight. The wrong way is to skip meals, resolve to eat nothing but diet bread and water, take diet pills, or make yourself vomit. You may make it through the end of the week and maybe even lose a pound or two, but you're unlikely to keep the weight off for more than a few months — if that. And inducing vomiting can lead to an eating disorder called bulimia, which can result in serious health problems. (See "On the Teen Scene: Eating Disorders Require Medical Attention" in the March 1992 FDA Consumer.)

"The more you deprive yourself of the foods you love, the more you will crave those foods. Inevitably, you'll break down and binge," says Jo Ann Hattner, a clinical dietitian at Packard Children's Hospital in Palo Alto, Calif. Then you'll not only gain those pounds back, you'll likely add a couple more.

Experts call this cycle of weight loss and weight gain "yo-yo" dieting. Obesity researchers believe that truly overweight people should continue to try to control their weight because studies are inconclusive on whether weight cycling is harmful, according to the National Institute of Diabetes and Digestive and Kidney Diseases. In contrast, the health risks from being overweight are well-known. Although the yo-yo effect may not hurt future weight-loss efforts, you need to make lifelong changes in eating behavior, diet, and physical activity.

Additionally, low-calorie diets that allow only a few types of foods can be bad for your health because they don't allow you to get enough vitamins and minerals. Kleinman warns that rapid weight loss from very-low-calorie "starvation diets" can cause serious effects in teenagers, such as gallstones, hair loss, weakness, and diarrhea.

About the Author

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