The Ultimate Way to Lose Weight: an Electrical Zap to the Brain

Eat protein and ditch the carbohydrate. Eat what you like for five days and fast for two. Live off grapefruit alone. Or consume only cabbage soup. We've tried innumerable diets over the years and they all suffer from one fundamental flaw – they require willpower. But what if we could somehow tweak the settings within our brain so we were able to eat less? Well, new research shows that may actually be possible.

A bunch of volunteers, given a dose of mild electrical ­stimulation to their brains for 20 minutes every day, consumed less food after a week. Quite a bit less. In the research, carried out at the University of Lübeck in Germany, male students were given the painless doses of electricity via electrodes placed on their heads. After a week, their calorie intake was reduced by 14%.

It's a response that surprised even the researchers involved. "I didn't think the reduction in ­calorie intake would be so much," says Professor Kerstin Oltmanns, who was involved with the research. The technique, known as transcranial direct current stimulation (tDCS), delivered a low current to specific region of the students' brains, their dorsolateral prefrontal cortex – an area on the outer surface of the brain at the front of the head.

The students, all of whom were a healthy weight, were told they were taking part in research into the effects of tDCS on mood and were given a buffet at the end of the week-long session to thank them for their efforts. They were unaware that the number of calories they consumed was being monitored. "Our next step is to explore whether it also works with obese ­people," she says.

The basic principle behind tDCS is fairly straightforward. When an electrical current makes its way through the scalp, it affects the brain region beneath. The current is too small to make the nerve cells, the neurons, fire. But it does put them in an altered physiological state, so they are more, or less, likely to fire depending on the type of stimulation given.

What's harder to fathom is the exact mechanism by which brain stimulation reduced the calorie intake in the students, although they did say that their appetites had dropped.

"Dieting doesn't work in the long term," says Oltmanns. "If people reduce their calorie intake, they lose weight. But in the long term, they will get the weight back in the weeks or months after ceasing the diet. I think the advantage of tDCS is that people don't have any more appetite for consuming more food, so they don't have to make any effort to stick to the diet. Unconsciously they lose weight. It's kind of a revolution."

But a different piece of research that's yet to be published points to another mechanism. It suggests that brain stimulation's slimming effects are down to the fact that it increases our willpower – our ability to resist temptation.

In the research, which will soon be published in the journal Appetite, female students in Brazil had the electrical activity measured inside their brains using an electroencephalogram (EEG) after a 20-minute dose of tDCS. The part of their brains stimulated, the dorsolateral prefrontal cortex, was just the same as was the effect – they ate less. But there was also an interesting pattern of electrical activity inside their heads. First there was less brain activity compared to when there was no stimulation, indicating that fewer brain cells were firing, then – just milliseconds later – more.

Associate professor Felipe Fregni at Harvard Medical School, who was involved with the research, has a theory on why that happened. He says tDCS may have dialled down the students' initial knee-jerk reaction to eat food when they saw it, while dialling up the activity in their prefrontal cortices, where they make rational, considered decisions. "The students ingested fewer calories because they could make more rational decisions," says Fregni.

It makes sense. After all, the dorsolateral prefrontal cortex is known to be an area of the brain where we inhibit temptations. It's the origin of rational thoughts that supress urges that might lead us astray.

"It's the part of the brain most developed in humans compared to monkeys and it relates to some of the more advanced abilities we have," says Roi Cohen Kadosh, a neuropsychologist at the University of Oxford who is another of the leading lights in tDCS research. "It's involved in learning and working memory and it's highly connected to other brain regions such as ones involved with addictions and rewards, and food is rewarding."

Cohen Kadosh has been investigating whether tDCS, when delivered to another brain region, the parietal lobe, can boost people's mathematical abilities. It seems it does. Over the past decade or so, there's been a surge of interest in brain stimulation research at universities around the world. There are studies showing it might help stroke patients recover, another showing it will help fighter pilots stay awake and focused over long periods. One scientist, Allan Snyder at the University of Sydney in Australia, even has ambitions of developing a 'thinking cap' that uses tDCS to boost creative thinking.

How long the positive effects of brain stimulation last appears to depend on how many times the brain is stimulated. "It's just like going to the gym," says Cohen Kadosh. "It depends on whether you go once, or day after day."

Only tiny amounts of electricity are used in tDCS – 1 to 2 milliamps ­– that's less than is needed to light a typical LED. But just how safe is it? "At the moment, it seems to be safe," says Cohen Kadosh. "My lab alone has done tDCS research on 700 subjects and there have been no adverse effects." He's even tried it on himself. "You feel a tingling sensation on your scalp for around 30 seconds and then you don't feel it any more as you habituate to it."

But Cohen Kadosh does have concerns about brain stimulation. "If you think about the brain as having limited capacity, if you shift resources to one brain region by stimulating it, maybe it will come at the expense of another brain region or cognitive ability."

There's early evidence that this may be the case. In one of Cohen Kadosh's studies, while brain stimulation increased volunteers' abilities to learn a list of artificial numbers, they were less able to process these digits – use them in another task – than volunteers who had learned them 'naturally'.

"There is a lot of excitement about brain stimulation but there are a lot of things as scientists we need to admit we don't know at this stage," says Cohen Kadosh. "We need more research to find out what the implications will be. We're not at the stage where people can really go home and plug their brain in and improve its function. It may happen in the future."

It may be a while before we use brain stimulation to get slimmer. There would need to be a host of clinical trials before it's sanctioned as an official treatment. So it leaves us plenty of time to consider whether we really want to amp up our brains to become the person we want to be.