Gary L. Wenk :
Anorexia nervosa, bulimia nervosa, binge eating disorder, and avoidant or restrictive food intake disorder are life-threatening psychiatric disorders that are generally difficult to treat. The lifetime prevalence of eating disorders such as anorexia nervosa and binge-eating disorder is 8.4 percent for women and 2.2 percent for men around the world. These data reflect diagnostic criteria based on clinical presentation in women and, therefore, most likely underestimate the prevalence in men. Women experience societal pressures that encourage and reward them for being thin; in contrast, men are encouraged to become large and muscular. These pressures often lead women to engage in purging after meals and excessive use of laxatives and diuretics to lose water weight. Women are exposed to higher rates of bullying, shame, and pressure to be thin. Men are more likely to exercise excessively and consume excessive amounts of dietary protein supplements that can damage the kidneys. Men often report being hesitant to seek help for their addiction to exercise or their pursuit of a perfect physique. For these reasons, eating disorders have a long history of being female disorders.
The unique genetic risks for females:
Studies have identified some genetic risk factors across sexes. For example, female relatives of men with anorexia nervosa have an increased risk of developing the same eating disorder. Twin studies, including same- and opposite-sex twins, report that about 50 percent of the genetic risk for eating disorders was shared. Most interesting, the females of male-female twin sets had a consistently higher genetic risk than the males of developing an eating disorder. Hormonal maturation is important given that the risk for females in these studies was undetectable until after puberty. In addition, having anorexia nervosa and carrying a large percentage of body fat are more genetically correlated in females than in males.Some recent studies have shown that individuals with eating disorders experience unique somatic deficits. These individuals may have either an increased or decreased sensitivity to internal body signals that inform them whether they are excited (is my heart racing?), anxious, frightened, or generally stressed.
These are important internal signals to distinguish from each other, given that emotional distress is implicated in the maintenance of both anxiety disorders and eating disorders. For example, a person with an eating disorder might have difficulty distinguishing feelings of guilt from feelings of stomach bloating. Studies have reported that individuals with eating disorders may find it challenging to distinguish between specific emotions and physical sensations. These individuals may engage in disordered eating strategies to reduce uncomfortable physical feelings associated with the uncomfortable emotions.
Advancements in our understanding of the causes of eating disorders should help clinicians to help their patients achieve recovery and stop feeling guilty about their bodies or behaviors.
(Gary L. Wenk, Ph.D., is a professor of psychology, neuroscience, molecular virology, immunology and medical genetics at the Ohio State University).
