Tonya Gilbert, age 14, of Santa Cruz, Calif., for her question:

WHAT IS ANOREXIA?

A person with a complete lack of appetite, who never becomes hungry even when using up energy, is said to have anorexia. Anorexiants are drugs that suppress appetite.

When a normal person becomes aware of an interest in food or a desire for food, he has an appetite. The difference between appetite and hunger depends on how long the individual has been without food and how much energy he has used.

Appetite is a rhythmic activity that usually occurs at fairly regular intervals throughout the day. But this activity may vary, depending on the controlling centers in the brain. Normal brain centers are sensitive to the temperature of our blood.

Anorexia usually occurs because of some type of emotional or behavioral problem.