By Elizabeth M. Holm

Learning more about our genetics has become both a fascination and a necessity for many of us. We can find out our heritage, learn our risk for specific diseases and predict which medications are right for us by examining our genetic makeup.

We know that the genes we inherit can make us more or less at risk for a variety of conditions including diabetes, depression and eating disorders. We also know that our genes predict our height, body shape and even body weight.

For the past couple of decades, we have known that eating disorders run in families and could have genetic factors. However, we have not known how to use this information in treatment and prevention.

Now we do. A large international study, published in Nature Genetics in July, identified eight areas on the genome that contain genes associated with anorexia nervosa and elucidated the psychiatric and metabolic genetic components of this devastating illness.

The researchers, led by Dr. Cynthia Bulik, discovered that genes which influence a person’s risk for anorexia nervosa are positively associated with genes for obsessive compulsive disorder and depression and inversely associated with genes that lead to a higher body fat and body mass index. Essentially, people genetically at risk for anorexia nervosa are not only more likely to develop OCD and depression, they are also more likely to have a metabolism that can lead to weight loss and low body fat.

These findings have huge implications for the prevention and treatment of eating disorders.

Anorexia nervosa is a life-threatening illness that affects male and female adolescents and adults. Sometimes it starts with healthy eating and a desire to eat fewer sweets and more vegetables, sometimes a person just wants to lose a little weight and sometimes it’s a combination of exercising more while eating less to improve athletic performance.

At some point, in some people, these seemingly innocent intentions trigger an illness that takes over a person’s life. No longer is that person free to eat when or what he or she desires. Instead a sinister, internal voice dictates which foods can be eaten and how much is acceptable. Eating becomes a set of rules and food becomes the enemy. Weight loss follows and leads to a dangerously low body weight.

Eating disorder professionals know that recovery from anorexia nervosa only happens when a person has regained the weight he or she has lost and returned to eating normally. The results of this genetic study help us better understand why this is so incredibly difficult.

Rather than being solely a psychological illness, this research provides evidence that anorexia nervosa is both a metabolic and psychiatric disorder. Persons with a high genetic risk may have a metabolism that flips an “anorexia nervosa switch” in response to an inadequate caloric intake and a negative energy balance.

We have known for a long time that dieting causes eating disorders. Not everyone who diets develops an eating disorder, but many do, and we now have a better understanding of why.

Elizabeth M. Holm, DrPH, RD is a registered dietitian and nutritionist in Alexandria. She can be reached at emholm@verizon.net.