It has been hailed as the latest magic bullet for slimmers - a balloon that is placed in the stomach and then filled with water.
The idea is that it makes the patient feel full and so reduces their desire to eat. Those who have tried the product say it has drastically cut their eating - and their waistlines.
And now the American invention is coming to the UK as part of a £4,000, six-month weight reduction programme.
A handful of British patients have already been fitted with the device, which is being marketed as a less invasive - and temporary - alternative to a gastric band. But experts have warned the balloon could cause a potentially fatal blockage.
The Elipse Gastric Balloon is swallowed while enclosed in a capsule attached to a hollow plastic tube.
A doctor uses ultrasound to check the balloon is correctly positioned, and it is filled, via the tube, with almost a pint of water. Finally, the tube is detached and removed. After 16 weeks, a valve sealing the device dissolves and the balloon deflates. It then passes through the intestines and out of the body.
The novel device is likely to appeal to those who are only modestly overweight, as it is being marketed at those with a Body Mass Index (BMI) of 27 or more - only two points over the 'healthy weight' threshold.
Monica Nava, 42, from Surrey, is one of the first Britons to have the device fitted. She has already shed more than a stone. She said: "It took me a few tries to swallow the capsule with a glass of water. After it's been filled you feel strangely heavy and full. But within a week, I'd stopped noticing it."
The Elipse, offered by The Private Clinic in Harley Street, is not without its critics. Paul Super, senior upper gastrointestinal surgeon at Birmingham Heartlands & Solihull NHS Trust, warned: 'If you made enough people swallow one, eventually you'd start to see people with the bag causing obstructions in the intestine, which requires major surgery to sort out.'
But Dr Samuel Levy, co-founder of US-based manufacturers Allurion, said: "We have treated hundreds of patients in Italy, France and the UK since December.
"None have had any problems. We are confident of its safety."