On the Teen Scene: Should You Go on a Diet?

by Ruth Papazian

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.

Diet Pills 

In 1992, FDA banned 111 ingredients in over-the-counter (OTC) diet products--including amino acids, cellulose, and grapefruit extract--after manufacturers were unable to prove that they worked.

A number of products (Cal-Ban 3000, Cal-Lite 1000, Cal-Trim 5000, Perma Slim, Bodi Trim, Dictol 7 Plus, Medi Thin, Nature's Way, and East Indian Guar Gum) were also recalled because they posed serious health risks. The products contained guar gum, which supposedly swelled in the stomach to provide a feeling of fullness. However, the swelling from the guar gum caused blockages in the throat and stomach.

In February 1996, FDA also proposed new warning labels for OTC diet pills containing phenylpropanolamine (PPA), including the statement that the product is "For use by people 18 years of age and older."

PPA is an ingredient found not only in many OTC diet pills but also in cough-cold and allergy products as well. FDA is concerned PPA may possibly increase the risk of a type of stroke (hemorrhagic) caused by bleeding into the brain, as was suggested by some reports of bleeding in the brain among PPA users, typically young women. This possible risk could be further increased if a person took more than the recommended dose of PPA, which might occur inadvertently from also taking a cough-cold product with PPA.

While FDA agrees that studies have not shown a definite link between PPA and stroke, the agency believes data from a more comprehensive study are needed to confirm the ingredient's safety. As a result, the OTC drug industry began a five-year study in 1994. 

Michael Weintraub, M.D, director of FDA's Office of Drug Evaluation V, says, "PPA is not recommended for use by teenagers also because they are still growing and if they suppress their appetite, they may not get proper nutrition." The author of studies on PPA published in scientific journals, Weintraub adds, "This is especially true of teens who don't need to lose weight but think that they do." 

The Real Skinny on Weight Loss 

If going to extremes won't do the trick, what will? Believe it or not, it's as simple as making a few changes in your eating habits to emphasize healthy foods and exercise--good advice even if you don't need to lose weight. 

Hattner describes a good diet as one that has balance, variety and moderation in food choices. She suggests using the U.S. Department of Agriculture's "Food Pyramid." These guidelines call for six to 11 servings a day of grains (bread, cereal, rice and pasta), three to five servings of vegetables, two to four servings of fruit, and two to three servings each of dairy (milk, cheese and yogurt) and protein-rich foods (meat, eggs, poultry, fish, dry beans, and nuts). (See "The Food Pyramid-Food Label Connection" in the June 1993 FDA Consumer.)

"The most important dietary change you can make is to limit the amount of high-fat foods that you eat," she adds. "Balance your favorite foods [which are usually high in fat] with fruits and vegetables [which are almost always very low in fat]; eat a wide variety of foods to keep from getting bored and to make sure your diet is nutritionally sound; and keep portion sizes reasonable so that you can have your [thin] slice of cake and lose weight, too."

To keep fat intake down, Hattner recommends making simple lower fat substitutions for the foods that you eat: Switch to 1 percent or skim milk instead of whole milk, nonfat or low-fat frozen yogurt or nonfat or low-fat ice cream instead of regular ice cream, and pretzels instead of corn chips. High-fat foods such as french fries, candy bars, and milkshakes that have no low-fat substitutes should only be eaten once in a while or in very small amounts.

Move It and Lose It 

Whether you are overweight or not, regular exercise (at least three times a week) is important to look and feel your best. If you do need to lose weight, stepping up your activity level will cause you to burn calories more quickly and help make weight loss easier.

"Exercise increases lean body weight. Also, you will appear slimmer as you develop your muscles because muscles give shape and form to your body," notes Hattner.

Fad or starvation diets and diet pills offer temporary solutions, at best. At worst, they may jeopardize your health. According to Weintraub, "The safest way for teenagers to control their weight is to eat a healthy, low-fat diet and get enough exercise."

Ruth Papazian is a writer in Bronx, N.Y. 

Publication No. (FDA) 97-1214