Millions of Britons could lose more than two stone by taking a pill which contains a balloon, a study suggests.

The results - unveiled at the world's largest obesity conference - showed it can be an effective alternative to weight loss surgery.

Experts said the NHS should now considering funding the pills for millions of Britons, with more than one in four obese.

After the pill is swallowed, the balloon swells up in the stomach when it is filled with water - restricting the amount of calories a person can eat.

The study of 42 adults found they lost two stone and six pounds on average after four months.