A first-of-a-kind weight loss treatment device has been approved by the U.S. Food and Drug Administration to treat obesity in certain obese adults.

The Maestro Rechargeable System, the first FDA-approved obesity device since 2007, targets the nerve pathway between the brain and the stomach that controls feelings of hunger and fullness. It is approved to treat patients aged 18 and older who have not been able to lose weight with a weight loss program, and who have a body mass index (BMI) of 35 to 45 with at least one other obesity-related condition, such as type 2 diabetes.

BMI, which measures body fat based on an individual's weight and height, is used to define the obesity categories. According to the Centers for Disease Control and Prevention, more than one-third of all U.S. adults are obese, and people with obesity are at increased risk of heart disease, stroke, type 2 diabetes and certain kinds of cancer.

"Obesity and its related medical conditions are major public health problems," William Maisel, deputy director for science and chief scientist in the FDA's Center for Devices and Radiological Health, said in a statement. "Medical devices can help physicians and patients to develop comprehensive obesity treatment plans."

The Maestro Rechargeable System consists of a rechargeable electrical pulse generator, wire leads and electrodes implanted surgically into the abdomen. It works by sending intermittent electrical pulses to the trunks in the abdominal vagus nerve, which is involved in regulating stomach emptying and signaling to the brain that the stomach feels empty or full. Although it is known that the electric stimulation blocks nerve activity between the brain and the stomach, the specific mechanisms for weight loss due to use of the device are unknown.

External controllers allow the patient to charge the device and allow health care professionals to adjust the device's settings in order to provide optimal therapy with minimal side effects.

The safety and effectiveness of the Maestro Rechargeable System were evaluated in a clinical trial that included 233 patients with a BMI of 35 or greater. The weight loss and adverse events of 157 patients who received the active Maestro device (the experimental group) were compared to 76 patients in the control group who received a Maestro electrical pulse generator that was not activated. The study found that after 12 months, the experimental group lost 8.5 percent more of its excess weight than the control group. About half (52.5 percent) of the patients in the experimental group lost at least 20 percent of their excess weight, and 38.3 percent of patients in the experimental group lost at least 25 percent of their excess weight.

The clinical study did not meet its original endpoint, which was that the experimental group lose at least 10 percent more excess weight than the control group. However, an FDA Advisory Committee (the Gastroenterology and Urology Devices Panel) found the 18-month data supportive of sustained weight loss, and agreed that the benefits of the device outweighed the risks for use in patients who met the criteria in the device's proposed indication.

In considering the benefits and risks of the device in its review of the Maestro Rechargeable System, the FDA considered the clinical study and the Panel's recommendations. Additionally, the Agency looked at an FDA-sponsored survey relating to patient preferences of obesity devices that showed a group of patients would accept risks associated with this surgically implanted device for the amounts of weight loss expected to be provided by the device.

Serious adverse events reported in the clinical study included nausea, pain at the neuroregulator site, vomiting, as well as surgical complications. Other adverse events included pain, heartburn, problems swallowing, belching, mild nausea and chest pain.

The Maestro Rechargeable System is manufactured by EnteroMedics of St. Paul, Minn.