A device to drain food from the stomach is the latest option for obese Americans who have been unable to lose weight via more traditional methods.

A new weight loss device offers a novel approach to cutting calories: draining them from the stomach before they are fully digested.

The AspireAssist system consists of a thin tube implanted in the stomach, connecting to an outside port on the skin of the belly.

About 20 minutes after finishing a meal, users connect the port to an external device, which drains some of the recently-consumed food into the toilet.

The manufacturer - Aspire Bariatrics based in Pennsylvania, US - says its system removes about 30 per cent of food stored in the stomach before it begins causing weight gain.

The Food and Drug Administration approved the device on Tuesday for adults who are obese, with a body mass index of 35 to 55, and have not been able to lose weight with other methods.

It's the latest option for millions of obese Americans who have been unable to lose weight via more traditional methods.

Obesity is considered one of the nation's leading public health problems because it can trigger diabetes and lead to heart disease and other serious health problems.

Last week the Centers for Disease Control and Prevention reported that rates of obesity among women had reached 40 per cent for the first time. That compares to a 35 per cent obesity rate for men.

The FDA said it approved the new device based on studies showing patients lost an average of 12 per cent of their total body weight one year after the procedure. That compared to 3.6 per cent weight loss for patients who didn't receive the device.

Side effects seen with AspireAssist included nausea, vomiting, constipation and diarrhoea.

"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," FDA deputy director Dr William Maisel said in a statement.

Weight loss surgery is recommended for those with a BMI of 40 or those with a BMI of 35 who have other risk factors like diabetes or high blood pressure.

Patients undergoing permanent weight loss surgery, such as gastric bypass surgery, generally lose about 34 per cent of their total weight after one year.

Weight loss is significantly lower with reversible banding procedures, in which a small saline-filled band is wrapped around the stomach to reduce its size. Those patients generally see weight loss of 14 per cent after one year.