10 to 20 percent above the ideal weight is considered mild obesity. More than that is defined as frank obesity. Many obese adolescents were overweight as children, maturing earlier than those of normal weight and achieving greater skeletal growth. Many others, however, were slim children and began to accumulate excess fat only in puberty. Some accumulation of fat in existing adipose (fat) cells in normal in puberty, especially in girls. In addition to this normal accumulation, the obese adolescent produces increasing numbers of adipose cells. Once puberty is over, the number of adipose cells is set in stone. They can be shrunk and enlarged, but they cannot be increased or decreased in number. That is why the odds against an obese adolescent becoming a normal- weight adult are 28 to 1.
In the teen years, appearance is of overriding importance, and obesity has a large role in that. Obese teenage girls are similar to many minority groups. They show passivity, withdrawal, and a self-image that is so poor as to verge on self-hatred. Obese teens are often teased by their fellow students and may be rejected socially. In addition, there is further discrimination against obese people in college admissions and the workplace. Boys have fewer problems with obesity than do girls, mainly because of their hormones, which encourage muscle augmentation rather than adipose augmentation, and partly because they tend to be far more active. Many obese teenagers have a caloric intake less than their slimmer counterparts, but do not engage in sports at all.
Dieting may be effective, but pure starvation is idiotic. This may result in massive weight loss, but the loss is not only fat. Muscle mass is lost as well, and that is much harder to gain back than fat, in addition to being desirable. The most effective approach to dieting is a combination of a reduced-fat diet and a healthy amount of exercise daily. Goals for weight loss should be realistic and short-term. Losses of more than 20 pounds a month would require some degree of nutritional deficiency.