Exposure to prenatal estrogen may precipitate disordered eating; after all, the males in these studies had far better

eating habits if their twin was male rather than female. Some researchers point out that female fetuses secrete sex

hormones that might trigger the expression of anorexia susceptibility genes, such as the one for the serotonin receptor

or those for related molecules. We know that estrogen has effects on genes in the brain, and we know that estrogen is a

pretty potent regulator of serotonin receptors, Klump says. Such a latent fashioning of the brain’s architecture and

functioning may explain, in part, the striking gender differences in anorexia. The possible in?uence of sex hormones also

suggests that relatively large-scale distortions in brain physiology may underlie anorexia.

WARNING TO YOUNG ATHLETES: NOT EATING ENOUGH CAN LEAD TO POOR PERFORMANCE AND A DANGEROUS

ADDICTION TO UNDEREATING.

Hunger Strikes
Environmental in?uences outside the human body might also pull genetic triggers for anorexia. One of these is likely to

be undernutrition itself. That is, a lack of suf?cient calories might be anYoung female athletes might be at particular risk

for anorexia. Some data suggest that dieting practices common among these athletes might turn on anorexia

susceptibility genes.

other on switch for anorexia susceptibility genes in addition to the surges of estrogen at puberty. Therapist Shan

Guisinger, who is af? liated with the University of Montana, pointed out that the growth spurts of puberty and, in many

cases, intense participation in athletics can boost the caloric requirements of teens far beyond what they are getting in

their diet. A 1999 study of 1,445 Division 1 NCAA athletes supports the idea that young female athletes might be at

particular risk. Craig Johnson, director of the eating disorders program at the Laureate Psychiatric Clinic in Tulsa, Okla.,

and his colleagues found that more than one third of the females they surveyed reported attitudes and behaviors that

put them at risk for anorexia, including dieting, using diet pills and wanting to have an abnormally low body-fat content.

In fact, these female athletes reported a mean body-fat content of 15.4 percent, a ?gure that is often below that required

for normal menses. But does starvation really propel a person toward anorexia, or might the anorexia-prone simply be

the ones who choose to exercise and eat too little? Supporting the former hypothesis is a renowned study conducted in

1944 by Ancel Keys and his colleagues at the University of Minnesota. To observe how to best refeed prisoners of war,

Keys recruited 36 young men and cut their caloric intake almost in half for 24 weeks. During that semistarvation period

the subjects obsessed, fantasized and dreamed about food. When they were allowed to eat normally again, the men

gorged and regained weight. Yet some started engaging in anorexiclike behaviors, including dieting and complaining

about too much fat around their bellies, thighs and buttocks. The study showed that deprivation, even in normal men,

could prompt the onset of anorexia in a small number who are predisposed to the condition. In case semistarvation can

spark the disorder, eating disorders experts now educate coaches and gym teachers to be on the lookout for young

athletes at risk. They tell coaches to counsel their charges that not eating enough can lead to poorer performance and,

worse, to a dangerous addiction to undereating. Meanwhile psychiatrist Christopher Fairburn of the University of Oxford

is tailoring a