The Need to Feed

THE BRAIN'S PLEASURE CHEMICAL MIGHT BE LINKED TO OVEREATING

Ever hear people threaten to eat an entire cake because they just can't stop themselves? While that may sound like a feeble excuse to overindulge, some chronic overeaters may lack control due to a shortage of a key brain chemical, say researchers from the Brookhaven National Laboratory in New York.

Dopamine, a neurochemical typically linked to mood, also plays a role in controlling appetite. It is responsible for transmitting reward signals within the brain in response to attractive stimuli including food, drugs and sex. "Obese subjects, however, seem to need to eat lots more food than a person of normal weight to feel satisfied and full," explains lead researcher Gene-Jack Wang, M.D., of Brookhaven Lab, whose research was recently published in The Lancet.

Using brain imaging, the researchers found that the heavier the individual, the less dopamine there is in his or her brain. So, overeating may be a desperate attempt to trigger that pleasurable sensation that follows a Thanksgiving dinner.

What remains unclear is whether obese people have fewer dopamine receptors to begin with, or if their brains have shut down some of the receptors in response to chronic overeating, in an attempt to prevent the release of excess dopamine. The hope is that the findings may one day lead to strategies aimed at improving dopamine function. "Right now, it's just a concept," says Wang. "We have drugs that modulate dopamine, but the problem is they're addictive." A safer route to go, he says, may be for people to join an overeaters support group. Or, better yet, to exercise--luckily, physical activity increases dopamine too.