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Federal health officials approved a new obesity device Wednesday that controls appetite with electrical pulses.

It’s the first new obesity device to be approved by the Food and Drug Administration in more than seven years. Yet doctors admit they aren’t quite sure how it works.

The surgically implanted device, called Maestro, is designed to interrupt hunger signals from the brain to the stomach, and it’s manually controlled.

“The Maestro Rechargeable System, the first FDA-approved obesity device since 2007, 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 of 35 to 45 with at least one other obesity-related condition, such as type 2 diabetes,” the FDA said in a statement.

Don’t look for it in stores – it’s likely only going to be offered at specialized clinics with trained surgeons. And don’t expect health insurance to pay for it any time soon, cautions NBC’s Diet & Nutrition editor Madelyn Fernstrom.

“Insurance likely, as with every new apparatus or pill, is not going to cover this,” Fernstrom says.

The device is implanted under the skin of the abdomen, with attachments placed just where the esophagus meets the stomach. It’s designed to interfere with the abdominal branch of the vagus nerve, a central nerve that controls the heart and digestive tract.

"VBLOC reduces feelings of hunger and promotes earlier feelings of fullness."

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The company that makes the device, EnteroMedics Inc., designed it to interfere with hunger signals using a technology called VBLOC.

“By blocking signals along the nerves that connect the brain and stomach, VBLOC reduces feelings of hunger and promotes earlier feelings of fullness, which can help people with obesity reduce the number of calories consumed and promote safe, healthy and durable weight loss,” said Dr. Scott Shikora, chief consulting medical officer for EnteroMedics.

It should work in theory, says Fernstrom, but in fact it is not entirely clear if the device is interfering with hunger or acting in some other way.

"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," the FDA said.

EnteroMedics has been struggling to get it to the market. It was shown to work safely enough in trials on patients, although they didn’t lose a huge amount of weight – about 8.5 percent of their excess weight compared to people implanted with a sham device.

The FDA wanted the device to be 10 percent better, on average, than a placebo but has approved it anyway.

“As part of the approval, the manufacturer must conduct a five year post approval study that will follow at least 100 patients and collect additional safety and effectiveness data including weight loss, adverse events, surgical revisions and explants and changes in obesity-related conditions,” the FDA said.

“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 agency added.

The need is enormous. More than two-thirds of Americans are overweight or obese and although there are several different drugs and devices on the market, most work best in limited populations such as the extremely obese.

“This is just another tool to put in the arsenal.”

Other devices include gastric bands that close off part of the stomach, a balloon that inflates inside the stomach, and various other surgical or stapling techniques to make the stomach smaller.

There's an appetite pacemaker, as well, that's approved in Europe but not the U.S.

Drugs include Qsymia, which pairs a stimulant with an epilepsy drug; Contrave, which pairs an antidepressant with an addiction drug, Belviq, aimed to make people feel fuller, and phentermine, an appetite suppressant.

“Everyone is not going to be a candidate for this,” Fernstorm said. “This is just another tool to put in the arsenal.”

It won’t stop overeating that isn’t related to appetite, for one thing. “Most people are not just eating for hunger,” Fernstrom said.