These clues can help diagnose anorexia in teens

Q: I'm worried about my 15-year-old daughter. She eats like a bird. She is very thin, but thinks she is fat. I'd like to think this is just a phase some teenagers go through, but could she have anorexia nervosa?

A: As with most illnesses, there is not a magic dividing line between having anorexia and not. In fact, there's a big gray zone where people don't meet the criteria for a disease, yet they're not normal, either.

An example is "pre-diabetes." Tens of millions of people in the United States have blood sugar levels that are not high enough to be called diabetes, but also aren't normal. It's important to recognize them, because such people have a higher risk for developing diabetes in the future.

It's the same with anorexia. People in the middle may meet some criteria for anorexia. They don't have an officially recognized eating disorder, yet they don't have a healthy relationship with food, either.

Many of these people have what a Harvard Medical School colleague calls "almost anorexia." It sounds as though your daughter may fit this description.

My colleague Dr. Jennifer Thomas, with Jenni Schaefer, has written an informative book on this topic called "Almost Anorexic: Is My (Or My Loved One's) Relationship With Food a Problem?"

What causes anorexia? We don't know.

Some psychiatrists have considered it a psychiatric disorder, strongly influenced by social pressures that equate beauty with thinness. I suspect it is predominantly a disorder of brain chemistry.

Could this just be a "phase" in your daughter's turbulent teenage life?

It's common for teens to worry about their weight and appearance. But consider the following red flags that increase the likelihood that your daughter has what Dr. Thomas calls "almost anorexia," or even full-scale anorexia:

• Does your daughter have drastic intentional weight loss or frequent weight changes?

• Does she follow rigid dietary rules, such as eating only at specific times or eating only a specific number of calories? And if she breaks these self-imposed rules, does she feel extremely guilty?

• Does your daughter occasionally force herself to vomit or use laxatives inappropriately? Does she sometimes exercise excessively to burn off the calories she just consumed?

• You've indicated that your daughter has a negative body image: She thinks she's fat, even though she's thin. Is that affecting how she lives her life? For example, is she reluctant to go swimming with friends because she is afraid to wear a swimsuit in public?

If you suspect your daughter may have - or almost have - anorexia, speak to her doctor. Indeed, her doctor may refer her to an anorexia specialist to decide if she has anorexia, or is at risk for becoming anorexic.

If so, now is the time to take steps to prevent it from developing. Eating disorders can cause serious medical problems, and in the most extreme cases, even death.

• Dr. Komaroff is a physician and professor at Harvard Medical School. For questions, go to AskDoctorK.com.