Cravings: How to Trick the Brain Into Thinking You're Full

Brain heart food
Eating some foods can make us feel more full. Then there are appetite suppressants. A gastric band, bypass and other forms of weight loss surgery can also cut cravings. Shutterstock

In the increasingly-dogged battle against obesity, people have resorted to all kinds of clever ways to trick their appetites. Eating some foods can make us feel more full. Then there are appetite suppressants. A gastric band, bypass and other forms of weight loss surgery can also cut cravings.

Now, approval has been given to the first obesity "electroceuticals", where electrical signals are used to trick the brain into thinking the gut is full. If their initial promise holds good, this approach could be a gentle option next to stomach stapling, which carries a 0.5% risk of death, would have fewer side effects, such as frequent diarrhea, and be reversible too.

Their target is the vagus nerve, a bundle of neurons that provides a major highway taking signals back and forth from the brain to many of the major organs. The vagus does a plethora of jobs, including helping to control heart rate, breathing, secretion of stomach acids and appetite. It also feeds information back to the brain on how various body systems are operating.

It is possible to wrap electrodes around the nerve in the neck and connect these to a power source programmed to switch on and off at intervals. While trying to do this to treat severe forms of epilepsy and depression it was found that people lost weight as a side effect, possibly because stimulation was mimicking the normal messages from our gut to signal to our brain that we are full.

Research on obese mini pigs published in 2010 by a team based in Rennes, France, showed that vagus nerve stimulation stopped the animals overeating and even made them select healthy food options. That year, a human pilot study by Jacek Sobocki at the Medical University of Warsaw, showed promise too.

Thin Ambitions
A device that is surgically implanted in the abdomen to control hunger is the next big step in fighting obesity. Science Photo Library

On 14 January, the US company EnteroMedics announced Food and Drug Administration approval for an implant. So-called VBLOC therapy intermittently blocks the signals of the vagus using the Maestro System, which is an implanted pacemaker-like device. A trial showed that, after a year, treated patients achieved 24.4% excess weight loss.

This is the first new medical device to be approved by the FDA for obesity in over a decade, said Scott Shikora, EnteroMedics' Chief Consulting Medical Officer. By blocking signals along the nerves that connect the brain and stomach, the device "promotes earlier feelings of fullness, which can help people with obesity reduce the number of calories consumed".

The US company IntraPace, in San Jose, also has European approval for its battery-powered Abiliti device. When food or drink is detected, this also delivers low-energy electrical impulses to the stomach that are intended to create a feeling of fullness.

Chris Toumazou and Sir Stephen Bloom of Imperial College London are trying a more elaborate approach which will be on display in Cravings: Can Your Food Control You?, a new exhibition opening in February at the Science Museum in London. The Imperial device, a microchip a few millimetres across, can also be implanted by relatively minor surgery and is attached using cuff electrodes to the vagus nerve within the peritoneal cavity in the abdomen. The cuffs go one step further than before because they read both electrical and chemical signatures of appetite within the nerve, offering more sensitivity.

The chip can then act upon these readings and send electrical signals to the brain, subduing the urge to eat. "It will be control of appetite, rather than saying 'don't eat'," said Toumazou. Though still too early to say when the new chip will be used in obese patients, electroceuticals offer a promising new way to curb unwanted cravings.