Building on research first done in Canada, human experiments are underway to test using jolts of electricity to the brain to keep obese people from overeating.

Deep brain stimulation involves boring through the skull and implanting electrodes the width of uncooked spaghetti in regions of the hypothalamus believed to control hunger and satiety, or feelings of fullness.

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© ReutersThe study of 10 men and women found that participants spent an average of 23 hours and 52 minutes sleeping, lying down or sitting each day.

A year ago, Toronto researchers reported the world's first attempt to treat obesity in a human with deep brain stimulation. Now, patients number two and three have been operated on in a Pittsburgh hospital, and a fourth is scheduled for surgery in the next month.

The idea is to use electrical brain implants "to get better weight control" by resetting the body's metabolism, says Dr. Don Whiting, a neurosurgeon at Allegheny General Hospital in Pittsburgh. Chicago researchers reported two years ago that the surgery resulted in "significant and sustained" weight loss in rats.

In the Toronto case, doctors did not see an effect on the man's weight. But, in a completely unexpected finding, they saw a striking effect on his memory: When they switched on the electrodes, the man experienced vivid flashbacks to events that occurred 30 years earlier. His scores on learning and memory tests shot up. Brain imaging showed the doctors were stimulating the memory circuit in the man's brain.

Based on that chance finding, the researchers have now tested deep brain stimulation on six patients with mild Alzheimer's disease. "So far, it looks very safe. No one has any serious problems, and it looks quite promising," says Dr. Andres Lozano, professor of neurosurgery at the University of Toronto and Canada Research Chair in Neuroscience at the Toronto Western Hospital.

Lozano's team is also testing deep brain stimulation on depression by targeting circuits in the "sadness" centre of the brain and the frontal lobes, which affect motivation. As well, thousands of patients worldwide have already undergone the brain surgery to treat Parkinson's and other movement disorders, and other researchers are experimenting on obsessive-compulsive disorder, epilepsy and Tourette's syndrome.

In the obesity experiments, all volunteers have failed gastric bypass, or stomach-stapling, surgery, and still are "morbidly" obese, meaning they have a body mass index greater than 40, or weigh at least 100 pounds above their ideal weight. So far, "they are, subjectively, definitely feeling less hungry," Whiting says. But subjective is a key word. It could be a placebo effect.

If the surgery proves effective, "it may be an alternative to bypass surgery down the road," Whiting says.

During deep brain stimulation, the skin of the scalp is anesthetized while the patient is still awake, and small holes drilled into the skull. Electrodes are implanted in the brain, and then tiny wires are tunnelled underneath the skin behind the ear and connected to a pacemaker-like device the size of a cookie implanted below the collarbone. The pacemaker can be controlled through the skin remotely.

Patients are asked to rate their hunger, on a zero to 10 scale. "As we move the electrodes through the brain into this area, we're able to see whether there's any spot where we can stimulate them successfully and reduce their hunger," Lozano explains. Once they find that spot, the electrodes are left in place and hooked up to the pacemaker.

Using the remote controls, doctors can switch the electrodes on or off, or increase or decrease the current, as if they were adjusting the volume on a TV. Serious complications are rare but can include bleeding and stroke.

Using brain stimulation for obesity is challenging, Lozano says, because there are many reasons why people overeat.

It might work for people who have an excessive appetite, "because we think that this area of the brain is particularly good at controlling appetite."

But the hedonistic aspect of eating - the pure pleasure of it - likely resides somewhere else in the brain. The same probably holds true for the addictive components of eating.

In the Toronto case, "we were able to get some effects on the patient's appetite," Lozano says. But the man wanted to turn his stimulator off because he felt it helped him sleep better, and "perhaps because he wanted to eat."

But Lozano, who helped train one of the Pittsburgh doctors now involved in the American experiments, believes it's worth it to keep trying. Doctors who specialize in obesity estimate that there are 1.5 million "super-obese" Canadians. Obesity increases the risk of diabetes, high blood pressure, heart disease, stroke and certain cancers.

"For the first time, our life expectancy as humans may be going down as a consequence of the high incidence of obesity in our population," Lozano says.