A hormone that can significantly decrease the appetite and reduce the desire for food by a third, has been discovered by scientists.

They hope it will provide a much safer and more effective weight loss alternative to extreme measures such as dieting pills or surgery.

The discovery that PYY3-36 suppresses appetite could be of huge benefit to those struggling with weight problems

Professor Stephen Bloom

The discovery is the result of a major collaboration between international teams of scientists based in the UK, US and Australia.

The hormone, PYY3-36, acts to inform the brain that the body is no longer hungry.

It is released from the cells lining the intestines after eating a meal - and the more you eat, the more hormone is produced.

Scientists gave a group of volunteers artificial infusions of the hormone at the same levels that would normally be expected to be produced following a meal - and then offered them a slap-up buffet.

They found that food intake was reduced by a third over the course of the following 24 hours.

Hunger levels

The volunteers were also asked how hungry they felt during and after the PYY3-36 transfusions.

Hunger levels dropped by up to 40% in the 12 hours after infusion.

It would not make a suitable weight loss drug due to its potential effect on other important systems of the body

Dr Roger Cone

Researcher Professor Stephen Bloom, from Imperial College London, said: "The discovery that PYY3-36 suppresses appetite could be of huge benefit to those struggling with weight problems.

"With over a billion people across the world now extremely overweight, it is vital this problem is tackled."

Professor Bloom said it might be possible to identify foods which cause the release of more PYY3-36, helping to limit appetite naturally.

Alternatively, it might be possible to create a tablet with a similar effect.

Co-researcher Professor Rory Shaw, medical director at Hammersmith Hospital, said: "We have always known that hunger is determined by complex interactions between the brain, hormones and enzymes in the gut.

"But this discovery - that administering a particular hormone can actually reduce appetite - is a major step forward on the road to the development of a new, safe and effective treatment for obesity."

More work needed

However, other scientists in the study said the experiment does not by itself prove that injections can safely control appetite or reverse obesity.

How the body might respond to elevated PPY3-36 levels over time is unclear.

Neurobiologist Dr Roger Cone, of Oregon Health Science University, said: "It would not make a suitable weight loss drug due to its potential effect on other important systems of the body."

The research is published in the journal Nature.