Dieting can become an obsession for some teen girls. For young female athletes — often those whose sports focus on weight and appearance — disordered eating can become the potentially serious “female athlete triad.”

When female athletes eat fewer calories than they burn, menstruation stops (amenorrhea). This leads to hormonal problems that can lower bone mass, eventually leading to stress fractures, infertility and osteoporosis. At its most serious, female athlete triad can leave a teen-ager with the bones of an 85-year-old.

Female athlete triad is essentially a nutritional problem. With the right diet, her cycle will return. If the problem is caught early, there will be no permanent damage. Unfortunately, few female teenage athletes want to eat more; even fewer actively want to menstruate. And, for teen-agers, the threat of osteoporosis just doesn’t register.

“Signs to look for include an irregular period,” says Dr. Joel Steinberg, a pediatrician on the medical staff at Children’s Medical Center of Dallas and director of the hospital’s weight guidance clinic. “Or if you notice that all the other signs of puberty are in place — breast buds, pubic hair, acne — but she’s still not menstruating, it’s probably time to see your pediatrician.” Other signs may include fatigue, stress fractures or other bone-related injuries.

When a girl enters Dr. Steinberg’s office with stress fractures, he asks her about her menstrual cycle and its regularity. He inquires about the patient’s diet, with questions designed to detect eating disorders. “If she weighed 130 a year ago, 115 now, and thinks she should weigh 105, she’s going the wrong way,” Dr. Steinberg says.

Once female athlete triad has been pinpointed, it’s important to get the female on the right nutritional plan. That’s not always easy. Here are a few suggestions:

“I tell young athletes they don’t have to eat much more, just reshuffle their eating habits. With proper nutrition, you gain a minimal amount of weight.

“I refer to food as fuel, and tell them it’s all about keeping fuel in your tank. Don’t overfill it, don’t let it run empty, don’t use the wrong kind of fuel,” Dr. Steinberg says.

Dr. Steinberg also recommends seeing a registered nutritionist, who can help design a diet to suit the athlete’s lifestyle, eating habits and preferences.