SSS 2011-06-01（在线收听）

This is Scientific American's 60-Second Science. I'm Karen Hopkin. This will just take a minute.

Meatloaf, mac-and-cheese or a big bowl of mashed potatoes. We all have our comfort foods. Except for people with anorexia. Food makes them extremely uncomfortable. Perhaps because eating causes a change in brain chemistry that instead of bringing pleasure makes anorectics feel anxious. That's according to a study in the International Journal of Eating Disorders.

For most people, breaking bread makes them feel good. That's because consuming food stimulates the release of dopamine, a chemical that tickles the pleasure centers of the brain. But for people with anorexia, meals are fraught with anxiety. So much so that some of these women, and the disease affects mostly women, actually diet themselves to death. But how could biology promote such behavior?

To find out, scientists gave volunteers a single dose of amphetamine, a drug that gets the dopamine flowing, and then looked at their brains. In women without an eating disorder, the boost in dopamine acted as expected, lighting up the brain's pleasure centers. But in women with anorexia, dopamine flooded a part of the brain that worries about consequences, thus fueling their anxiety. Seeing where this anxiety comes from could be the first step to help making it disappear.

Thanks for the minute. For Scientific American's 60-Second Science, I'm Karen Hopkin.