Most people enjoy a chocolate bar with just a twinge of guilt and go about their day, but for women who binge eat, cravings for such concoctions can be overwhelming.

A University of Michigan nutritionist is out to change that, hunting for a drug to nip those cravings at their source in the brain and thus battle certain eating disorders."It's possible that we may be able to control the onset of binges," said Adam Drewnowski.

At issue are not people who just need to shed weight, but sufferers of medically defined disorders that cause severe food cravings and huge eating binges, often followed by vomiting or laxatives to fight the resulting pounds. About 1 million Americans, mostly women, suffer from one such disorder, bulimia.

Antidepressants that affect the brain chemical serotonin offer help to some binge eaters, but not all, and they can cause side effects. So doctors are looking for better alternatives.

Women who binge most desire foods high in fat and sugar - chocolate is No. 1 - while men crave foods high in fat and salt, nutrition surveys show.

Now Drewnowski has linked those chocolate cravings to a brain chemical that gives women physical pleasure from the sweet and found that blocking production of those chemicals may also block the binge.

The brain naturally produces opiates, druglike chemicals that cause pleasure sensations and are linked to addictions. The chemicals make the person want to eat sweets, and eating such foods produces even more of the opiates.

Animal studies showed the link with sweet fats: Rats who drank chocolate milk immediately produced more opiates. But when their normal opiate production was blocked, rats chose their normal feed over previously tempting sweets.

Intrigued, Drewnowski tested the theory on 41 women, bingers and normal eaters. They were offered their favorite foods, from pretzels and jelly beans to chocolate chip cookies and chocolate ice cream. Half received injections of naloxone, a drug used to treat heroin overdoses because it blocks brain opiate receptors. The rest got a placebo.

Naloxone made bingers eat notably less - an average of 160 fewer calories per meal, Drewnowski reported in July's American Journal of Clinical Nutrition. Their chocolate consumption dropped in favor of lower-fat foods like popcorn. When asked to rate their favorite foods again, chocolate dropped.

Non-bingers, however, weren't affected.

Naloxone is available only intravenously, making it impractical for chronic bingers. Drew-now-ski is searching for an easier-to-take drug.