An obesity pill that expands into a gel almost 100 times its original size after being swallowed has moved one step closer to approval.

The product is called Gelesis100 and is a capsule that contains little particles made up of cellulose, a fibre found in plants, and citric acid, which is found in fruits.

When the particles come into contact with water, they soak up more than 100 times their weight and form a super-absorbent hydrogel, similar in consistency to tapioca pudding.

This fills the stomach and creates a sensation of fullness, resulting in the patient eating less food.

Late-stage trial results unveiled this morning suggest the pill is good at helping people lose weight, with 60pc of those who were administered Gelesis100 losing just over 20lbs, or 10pc of their body weight, in six months. Those patients with pre-diabetes or early diabetes lost on average 30lbs.

The company behind the pill is US-based Gelesis. It is 20pc owned by London-listed biotech Puretech.

Should the medication win clearance from American and European regulators, it could hit the market in two years.

Unlike other prescription weight-loss products on the market, Gelesis100 is classified as a device, rather than a drug, because it is not absorbed into the body.

Instead, it stays in the stomach and intestine, where it is broken down and passed through. It does not interact with other drugs or alter chemical processes in the body.