What BMI and Weight Are Anorexic?

A serious medical condition characterized by an unhealthily low body weight, abnormal obsession with food and distorted body image, anorexia nervosa needs attention from a medical professional. Body weight and body mass index can help determine whether a person has the disorder, but other symptoms serve as clues that the problem of undereating and near starvation exist. A person with anorexia nervosa may be in denial, and only a parent, friend or other loved one can convince her to seek treatment.

A body weight that is 15 percent or more below average for height, age and gender indicates the possibility of the eating disorder.

Body mass index, or BMI, measures the relationship between height and weight. It's a way to evaluate whether a person is of normal weight, overweight or underweight. Healthy adults usually fall between 18.5 and 24.9 on the BMI chart. A BMI below 18.5 signals a problem may exist, while a BMI below 17.5 -- especially in adults -- is usually present in people with anorexia nervosa. Some doctors may show concern if BMI falls below 20, especially if other disordered eating symptoms are present.

In young teens, a low BMI is not enough to diagnose anorexia nervosa. Some young teen girls simply have slender builds and haven't reached adult proportions but are completely healthy.

A doctor may present a suspected eating-disorder patient with a series of questions known as the SCOFF questionnaire. Positive answers to these questions often indicate anorexia nervosa or bulimia, a disorder characterized by binge eating and purging. The questions address if you've recently lost a notable amount of weight; your preoccupation with weight; whether you make yourself vomit after meals; the status of your menstrual cycle and if it's stopped; and ask about your image of fat vs. thin body types, especially your own.

Oftentimes, getting straight answers from people with eating disorders is challenging. They either don't perceive they have a problem or don't want help. Refusal of a person to try and maintain a normal body weight; fear of becoming fat; denial of the state of their body; and loss of menses for three months or longer are other behaviors indicative of anorexia.

A severely underweight body and the unhealthy eating habits that go along with an eating disorder can have serious health consequences. People who are underweight are more vulnerable to illness, have a low muscle mass and may lose hair. Restricting food intake deprives the body of valuable nutrients that support a healthy body, including strong bones, sexual function and brain health.

Being severely underweight can put a person's heart at risk, too. A low pulse and blood pressure, as well as reduced body temperature can be complications of the eating disorder. If someone is suspected of having the eating disorder, a doctor will likely test her muscle strength by observing her ability to move from a squat to a stand. An electrocardiogram will assess whether there is an irregular heartbeat as a result of unhealthy eating habits. Electrolyte imbalances, low protein status and thyroid, liver or kidney issues are other medical concerns associated with anorexia nervosa.

If you or a loved one seem to be at risk of developing the disorder, get treatment right away. A visit to a general practitioner may be your first step, but intervention from a specialist may be required.

In some cases, severe weight loss occurs because of another physical or emotional condition. Today's Dietitian notes that depression often occurs in conjunction with rapid weight loss and loss of appetite. Consider seeking a combination of medical and mental health care to address disordered eating.