The system, called Maestro, works in a pretty interesting way: It's implanted in the abdomen, where it sends electrical pulses along the vagus nerve. Normally, signals going through this nerve communicate to the brain whether or not the stomach is empty or full. By manipulating those signals, the system can create feelings of fullness earlier, encouraging patients to take in fewer calories. Using an external controller, the patients' doctors can also vary the strength of the signal.
Obviously, this isn't for someone who just wants to lose a couple pounds. Instead, the Maestro would be reserved for cases in which patients have a BMI over 35, haven't been able to lose weight after making healthy lifestyle changes, and have at least one obesity-related condition (such as Type 2 diabetes). Although getting an implant sounds kind of intimidating, the process is actually much less invasive (with fewer chances for complications) than getting bariatric surgery — which would be the alternative in most cases.
In one clinical trial involving 233 patients, half of those given the device lost about 20% of their excess weight. After a year, those patients had lost 8.5% more weight than the control group. But, those results didn't quite meet the study's original goal of 10%. So, even though the Maestro has been approved (meaning the system's potential benefits currently outweigh its risks), the FDA is calling for another big, five-year study as part of its approval process. Stay tuned.