University of Pennsylvania researchers are the first to show that mild electrical stimulation of the brain's reward center can induce weight loss by curbing both binge eating and overeating.

In obese mice.

Mice, of course, are not people. Many treatments that work wonders in rodents are ineffective in humans. A classic example was the 1995 discovery of the hormone leptin; it melted away fat in obese mice, but flopped in human trials.

Nonetheless, Penn neurosurgeon Casey H. Halpern, who led the new mouse study, is confident that deep brain stimulation could help obese humans because, with pleasures such as gluttony, we are all animals. "The reward circuitry in animal and human brains has significant overlap," he said.

Deep brain stimulation involves implanting electrodes in the brain that are controlled by a pacemaker-like device placed in the chest. It has been approved to treat Parkinson's disease, and is being studied for many other conditions.

Using it to fight fat is still "a bit fringe," Halpern conceded.

The Penn mouse study, published last week in the Journal of Neuroscience, focused on a brain structure called the nucleus accumbens. Past work suggests that reward-seeking behavior, such as binge eating, causes this area to release dopamine, the brain's pleasure signal.

The Penn study, conducted in the lab of neuroscientist Tracy L. Bale, theorized that electrically stimulating the nucleus accumbens would release dopamine and blunt the rodents' urge to overeat.

The first subjects were binge eaters that had plenty of regular food, but had a habit of gorging on high-fat chow for only an hour a day. When their brains were stimulated in that hour, they downed 75 percent less junky food.

A second group of mice ate a high-fat diet for 16 weeks, becoming obese and diabetic. Their brains were then stimulated continuously for four days. "The mice ate less, lost weight, and their diabetes got better," Halpern said.

Now, Halpern is debating whether to test deep brain stimulation in larger animals - or seek permission for a human trial. "We have so many people who are dying of obesity. So is it ethical to wait" for more animal results?