By Dr. Ismael Nuno, Special to CNN; May 9, 2013 — Updated 1129 GMT (1929 HKT)

(CNN) — “Oh my God, I eat like a horse and look like an overstuffed elephant.”

These were words commonly used by teenagers at my daughter’s school. In 2009, the Centers for Disease Control and Prevention’s Youth Risk Behavior Survey found that 33% of girls in high school think they are overweight, while 56% of them said they were actively trying to decrease their weight.

Young girls with eating disorders classically see themselves as being overweight or obese. They severely decrease their caloric intake while aggressively increasing their physical activity to burn any calories they may consume.

Cardiac complications are a possible result of the severe protein deficiency associated with eating disorders. The electrical activity of the heart becomes abnormal, and the transmission of the electrical impulse is either retarded or not present at all. This can cause sudden cardiac death.

My 18-year-old daughter, Catharine, died in 1995 in Los Angeles after a four-year fight with anorexia nervosa.

She had been hospitalized at National Children’s Medical Center in Washington. It was a comprehensive unit with pediatric nurses, metabolic experts and psychologists, all dedicated to young girls with eating disorders. All of the patients looked like they were cut out with a cookie cutter — small and thin.

When we moved to Los Angeles, she continued her care at UCLA and had psychiatric visits as an outpatient. She continued to battle her eating disorder but eventually lost the war. She developed a cardiac arrhythmia that eventually killed her.

As a father, I look back at those moments when I saw a young girl fight for her life. I admired her, respected her and remember her every day. I look at the efforts being made today by physicians and specialists in eating disorders and smile because this disease is now better understood.

As a parent of one of these young girls, I can warn other parents of some possible red flags. These red flags can come in the form of behavioral changes or changes in eating habits. If they see them, parents should seek help for their child.

Behavioral changes:

  • The teenager will go on a diet and comment that other girls at her school are doing the same.
  • He or she may become withdrawn or more shy than they usually are. They become quieter, have fewer opinions and decrease their socialization.
  • They become fussy in their daily activities. They constantly clean their room or groom themselves. They “overclean.”
  • There is a definite increase in physical activity. Some of them may join the track team or join some other sport and become aggressive in practicing. They become very competitive and often successful at their sport.
  • Academically, they are also very competitive and maintain a high grade-point average. They are as aggressive academically as they are physically.
  • Daughters start to act like their mothers in appearance and behavior.

Eating habits:

  • There is a subtle decrease in the amount of eating at dinner time, or they eat at a separate moment. There is a progressive decrease in their caloric intake.
  • They will begin to try new food products that are low in calories and nutrition. Then there is no breakfast, lunch or dinner because they are already “too full.”
  • They drink a lot of water to fill their stomachs. Water has no calories and is filling.
  • They excuse themselves to go to the bathroom immediately after a meal to unload their caloric burden by inducing emesis, or vomiting.