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The Food and Drug Administration approved a new and unusual weight loss device Tuesday: an external pump that dumps part of the stomach contents into the toilet.

Some critics have called it “assisted bulimia” but the device, approved for use in very obese patients, helps them lose on average more than 12 percent of body weight — far more than pills or most diets.

The Food and Drug Administration approved an external pump that dumps part of the stomach contents into the toilet called Aspire Assist. Aspire Bariatrics

The device is considered minimally invasive and includes a tube that goes from the inside of the stomach to a port on the outside of the abdomen. The pump can be attached to the outside port as needed to remove about a third of the stomach’s contents at a time.

Aspire Bariatrics of King of Prussia, Pennsylvania, which makes the device, has a video about it here.

Clinical trials showed patient lost an average of 46 pounds during the first year and another few pounds to make 50 pounds of weight loss by the second year.

“The AspireAssist device should not be used on patients with eating disorders, and it is not intended to be used for short durations in those who are moderately overweight,” the FDA said in a statement.

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“It is intended to assist in weight loss in patients aged 22 and older who are obese, with a body mass index of 35 to 55, and who have failed to achieve and maintain weight loss through non-surgical weight-loss therapy.”

Dr. Shelby Sullivan of Washington University in St. Louis, who helped test the AspireAssist and several other medical devices, as well, says it's a good option for the extremely obese. She disputes critical descriptions about how the device works.

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"There is no such thing as medical bulimia or assisted bulimia," Sullivan told NBC News. Bulimia is an eating disorder defined by overeating and then purging, often though forced vomiting.

"Patients eat less with this therapy then they did before," she said. "People think patients can eat whatever they want and then aspirate it and that’s just not true. It has to be liquid enough and the particles have to be small enough to get through the tube."

The device joins a growing list of new ways to help Americans lose weight, from carefully controlled diets to surgery and a batch of devices that make the stomach smaller in effect.

“The AspireAssist device should not be used on patients with eating disorders."

Diet drugs don’t work terribly well and doctors are reluctant to prescribe them. This new device is the first to remove food that people have already eaten before it can be digested.

The need is growing. The latest data from the Centers for Disease Control and Prevention shows that 38 percent of U.S. adults are obese, while 17 percent of teenagers fall under that category.

“The AspireAssist approach helps provide effective control of calorie absorption, which is a key principle of weight management therapy,” said the FDA’s Dr. William Maisel.

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“Patients need to be regularly monitored by their health care provider and should follow a lifestyle program to help them develop healthier eating habits and reduce their calorie intake,” he added.

The company has not said how much it will charge for the device, which is on the market in Europe. A surgeon will also have to implant the device in a short endoscopic procedure, and that cost may vary by center.

This new device is the first to remove food that people have already eaten before it can be digested.

“Patients require frequent monitoring by a health care provider to shorten the tube as they lose weight and abdominal girth, so that the disk remains flush against their skin. Frequent medical visits are also necessary to monitor device use and weight loss and to provide counseling on lifestyle therapies,” the FDA noted.

Side effects include indigestion, nausea, vomiting, constipation and diarrhea.

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Obesity is calculated using body mass index (BMI) — a measure of height to weight — that's a score of 30.

People are considered overweight when their BMI hits 25.

Someone who is 5-foot-5 and weighs 149 pounds has a body mass index of 24, considered a healthy weight. Add a pound and the same person has a BMI of 25 and is considered overweight. At 180 pounds this person has a BMI of 30 and is considered obese.

The National Institutes of Health has a BMI calculator online here.