Switched-on diet: a 'pacemaker' will make the brain think you've eaten enough / Getty

Blocking the electrical signals sent by the digestive system to the brain can fool us into feeling full

In January 2015, the US Food and Drug Administration approved a new kind of obesity therapy. Vbloc is a vagus nerve pacemaker developed by EnteroMedics, a company based in St Paul, Minnesota. It works by intermittently blocking vagal nerve signals between the brain and the stomach. The idea stems from the observation of weight loss among patients who had their vagus nerve cut just below the diaphragm, once a common treatment for duodenal ulcers, because it reduces acid secretion.

Instead of cutting the vagus nerve, Vbloc positions the pacemaker wires on the nerve between the oesophagus and the stomach. Then a pacemaker provides a nerve-blocking stimulus for 14 hours a day. Because the vagus nerve carries information about digestion and fullness to the brain, the theory is that faulty signals can fool the brain into thinking the body needs more food, so people eat more than they actually need. Blocking the vagus nerve stops these faulty appetite signals from reaching the brain, which reduces hunger and promotes a feeling of fullness.

Scott Shikora, the chief medical officer at EnteroMedics comments: "The patients in our trial that were receiving vagal nerve blocking didn't eat different foods, they just had less appetite, so ate less."

Mike Magnant, a machinist from Carver, Massachusetts, was one of more than 200 patients in the Vbloc trial. Magnant had battled with obesity since his teens, tried numerous diets and diet pills, yet at 5ft 6in tall, he weighed 132kg (20st 11lbs) – a body mass index of 47. "Every new diet I tried, I'd lose 20lbs and then within a few months, I'd put 25lbs back on," he says. "Just bending over to tie my shoelaces was exhausting, climbing stairs was an issue, fitting in a plane seat or at a restaurant booth was impossible, and I was suffering from high blood pressure."

In 2011, Magnant heard a radio ad for candidates to be part of a blind clinical trial for weight loss. He went along to a meeting to see the device and learn more. And he was impressed: "This actually sounded like it might work. It was cutting-edge and like sci-fi to use a pacemaker to tell your brain you were full. I thought, 'Wow, this is cool'! I had the surgery on Friday 2 December, and on Monday I was back at work. Friends who have had gastric bypass have been off work for at least six weeks."

And the results were similarly speedy. "By Christmas, I was struggling to eat the family dinner – I just wasn't hungry. Before the surgery I was eating at least 3,000kcal per day and still not feeling full; since, I rarely eat half of that. In the first month I lost 8lbs, and after a few months everyone noticed, but I kept the device secret at first in case all the weight piled back on again," he says.

Magnant went down to 206lbs, but says people complained he was "looking very thin and drawn", so he has settled at being a bit heavier and says he is comfortable with this. "I walk three miles a day, I climb three flights of stairs, I don't feel people are looking at me because of my weight – it's a brand new experience. I'm 63 and I feel as though I can do anything."

Trials of the device in people with a body mass index of greater than 35 showed that more than half lost meaningful weight – and they kept it off for at least the 18 months of the study. Unlike a gastric bypass, the vagal implant is fully reversible, doesn't require a major dietary change and doesn't cause "dumping syndrome", in which food moves too quickly from the stomach to the bowel, or hypoglycaemia (low blood sugar). Shikora points out that less than one per cent of potential candidates for bypass surgery actually have it because of the risks and lifestyle changes involved. "But this could offer a simpler, safer weight loss alternative for patients."

"My life has completely changed," says Magnant. And this is partly because it no longer revolves around food: "Before, I'd stop at a fast-food restaurant on my way home from work, eat a couple of burgers, then go home and have dinner. Now, I'm not hungry enough to want to do that. I've saved a lot of money," he laughs.

A version of this article first appeared on mosaicscience.com