As obesity rates soar, the hunt for innovative interventions is more pressing than ever. According to a recent paper, a tiny, battery-free implant could offer fresh hope.

Obesity is a growing concern; today, experts class well over one-third of people in the US as obese.

Globally, an estimated 4 million people died of conditions related to a high body mass index (BMI) in 2015 alone.

These worrying trends mean scientists are focused on understanding the causes, risk factors, and implications of obesity.

The reason why obesity develops in certain people and not others is multifaceted, involving genetic, hormonal, and psychological factors, among others.

The direct cause of excess weight, however, is the ingestion of more calories than the body uses. Some scientists are trying to find ways to trick the brain into consuming less food.

New implantable technology

Recently, researchers from the University of Wisconsin-Madison tested a groundbreaking, high-tech solution.

The scientists designed a small, implantable device that they hope will reduce hunger pangs and help people lose weight.

The device, which is less than 1 centimeter across, can be implanted using a minimally invasive technique.

Consisting of a flexible nanogenerator, it sends small pulses of electricity through the vagus nerve, which passes messages between the stomach and the brain.

This mild stimulation convinces the brain that the stomach is full and reduces feelings of hunger.

Importantly, the device does not need a battery or charging. Instead, it gets its power from the churning motion of the stomach during peristalsis.

Because the movement of the stomach provides the device with its power, it only works when the arrival of food causes the stomach to move; this means that the device is only active at the precise time its signals will be effective.

"The pulses correlate with the stomach's motions, enhancing a natural response to help control food intake," explains author Xudong Wang, who is a professor of materials science and engineering.

To test the device, the researchers used a rat model, and they have published their findings in the journal Nature Communications. The results have encouraged the authors, as they explain:

"We successfully demonstrated this strategy on rats and achieved 38% weight loss in as short as 15 days without further rebound, exceeding all current electrical stimulation approaches."

No obvious safety issues

Importantly, the implant stayed in the correct position throughout the 12-week trial. Furthermore, there were no measurable negative impacts on the rats' kidney or liver functions and no signs of infection.

The researchers carried out postmortem examinations on most of the animals' vital organs and found no adverse effects.

When they compared the implant with other weight-loss devices, it had several benefits. Gastric bypass surgery, for instance, permanently reduces the capacity of the stomach, whereas, the new implant is fully reversible, and the implant procedure is much less invasive.

This is not the only implant that stimulates the vagus nerve to reduce hunger pangs. There is a competitor that goes by the name of Maestro, which the US Food and Drug Administration (FDA) have approved. However, Maestro requires ongoing maintenance and up to 3 hours of charging each week.

The new implant has no battery or wiring, as Wang explains, "It's automatically responsive to our body function, producing stimulation when needed. Our body knows best."

Also, Maestro uses high-frequency jolts to completely shut down the vagus nerve, rather than the intermittent pulsing of the new technology. Because the newer implant only works when it needs to, the body is less likely to overcompensate, which, in the case of Maestro, can slowly reduce how effective it is over time.

Of course, there is a long path between here and use in humans, but the authors are keen to continue their investigations. Next, they plan to trial the device in larger animals.