An implantable device that blocks a stomach nerve has shown promise in treating obesity in a less invasive way than traditional surgery, a study has found.

The device is implanted under the skin in the abdomen and is regulated by patients through a switch.

It emits a low-level electrical charge that blocks the vagal nerve, which signals a person when to eat. This blocking causes obese patients to feel full after a normal-sized meal rather than to continue eating.

The study, a collaborative effort by the Mayo Clinic and researchers in Norway, Mexico and Australia, is published in the June issue of the journal Surgery. EnteroMedics, the manufacturer of the device, funded the research.

The device is being touted as a less invasive alternative to bariatric surgery, in which the stomach is surgically decreased in size or removed. It is reversible, unlike the surgery, and can be shut off by patients during the night.

According to researchers, there is no damage to the vagal nerves or stomach.

Followup study underway

In the study, 31 obese patients who wore the device over six months in three medical centres lost an average of almost 15 per cent of their weight.

The researchers are working on a followup double-blinded study involving 300 patients.

"All patients will have the device implanted, but one-third will not have it turned on during the first year of the study, so that after meals, it won't be blocking the nerve signals; this is called 'sham' treatment," said Michael Camilleri, a Mayo Clinic researcher who helped design the study.

"Neither the patients nor their doctors will know whether the blocking signals are going through or not. This pivotal study will tell us whether a placebo effect is responsible for some of the weight loss."

The research centres that conducted the study are Flinders Medical Centre in Adelaide, Australia, Instituto Nacional de la Nutricion in Mexico City and St. Olav's University Hospital in Trondheim, Norway.