"New battery-free, easily implantable weight-loss devices developed by engineers at the University of Wisconsin–Madison..."

"... helped rats shed almost 40 percent of their body weight... Measuring less than 1 centimeter across... the tiny devices — which are safe for use in the body and implantable via a minimally invasive procedure — generate gentle electric pulses from the stomach’s natural churning motions and deliver them to the vagus nerve, which links the brain and the stomach. That gentle stimulation dupes the brain into thinking that the stomach is full after only a few nibbles of food.... Unlike gastric bypass, which permanently alters the capacity of the stomach, the effects of the new devices also are reversible. When [UW professor Xudong Wang] and his collaborators removed the devices after 12 weeks, the study’s rats resumed their normal eating patterns and weight bounced right back on. Wang’s device has several advantages over an existing unit that stimulates the vagus nerve for weight loss. That existing unit, 'Maestro,' approved by the Food and Drug Administration in 2015, administers high-frequency zaps to the vagus nerve to shut down all communication between the brain and stomach. It requires a complicated control unit and bulky batteries which frequently must be recharged. That ongoing maintenance can be a big barrier to use, says Dr. Luke Funk, a surgery professor in UW–Madison’s Division of Minimally Invasive, Foregut and Bariatric Surgery...."

UW press release.