Scientists investigating a hunger-regulating hormone that can cut the amount people eat by up to a quarter have won a £2.2m award to produce a chewing gum to combat obesity.

Professor Steve Bloom, of Imperial College London, who has spent more than 20 years studying the control of appetite, said the naturally occurring gut hormone was one of the most promising weapons for tackling obesity. It has so far only been used experimentally but the long-term aim was to develop it into a chewing gum or nasal spray that might be taken for life.

Two thirds of the adult UK population are overweight or obese and the condition causes 1,000 deaths a week. The pandemic was getting worse and there were no solutions in prospect, said Professor Bloom. If successful, a hunger-regulating treatment would represent a major advance against bulging waistlines and could become a billion-dollar earner for its makers.

But drug companies were not interested because it is a naturally occurring hormone and cannot be patented. The hormone, pancreatic polypeptide (PP), is produced by the pancreas after every meal and sends a signal to the brain that the stomach is full.

People with benign pancreatic tumours who secrete large quantities of PP remain chronically thin but have no other side effects, said Professor Bloom. When the hormone is given to volunteers who are then allowed to eat as much as they like, the amount they eat is reduced by between 15 and 25 per cent .

"Developing a treatment based on natural appetite suppression, mimicking our body's response to being full, has the potential to be safe and effective. We believe pancreatic polypeptide may be the answer," he said.

The hormone appeared to have no side effects which was crucial for a treatment that might be taken long-term. People with PP-secreting tumours who had lived with high levels of the hormone for more than a decade suffered no ill effects other than being thin.

Professor Bloom published results of his research in The New England Journal of Medicine in 2003 but has struggled to find funding to proceed to clinical trials.

Now the Wellcome Trust has given him its first "seeding drug discovery" award to develop the treatment. It cannot be taken as a pill because the hormone would be destroyed in the stomach but the aim is to create a long-acting injectable drug that would be both practical and patentable. It would be available on prescription only - to prevent anorexic girls getting hold of it - initially for the clinically obese.

Existing obesity drugs achieved weight loss of a few pounds after a year of treatment but there was no further reduction, Professor Bloom said. Bariatric (stomach-reducing) surgery was risky. A hunger-regulating hormone could be given in a large dose initially to promote rapid weight loss of 5-10 per cent and then be reduced to a maintenance dose to keep weight down.

"People with a propensity to overeat might have to take this for life. But its effects wouldn't be permanent - they could be reversed at any time by stopping it," said Professor Bloom.

The Wellcome Trust is investing similar sums in developing two other drugs, against cancer and against superbugs such as MRSA, as part of a £91m "technology transfer" programme which aims to get ideas from the laboratory into clinical trials.

Ted Bianco, director of the programme, said: "It is one thing to have a eureka moment in the lab but another to have a white powder in your hand that can be tried as a drug."