Hormone injections could be available within five years to help obese people slim, a researcher predicted yesterday.
Rachel Batterham suggested that the daily jabs, costing around £20 a day at current prices, might be used in the same way as insulin injections.
Dr Batterham was the lead author of a study published in the New England Journal of Medicine last night revealing that many obese people had lower than average levels of the hunger-regulating hormone PYY3-36.
A team from Imperial College and Hammersmith hospital in London found that infusing the hormone, which occurs naturally in the gut, reduced the consumption of calories by about 30% in tests on a group of lean and obese volunteers.
Dr Batterham - a clinical research fellow funded by the Wellcome Trust, who has since moved to University College London - stressed that far more work was needed.
"This is the first time that a hormone has been shown to cause a long-term reduction in calorie intake in obese volunteers," she said. "We now need to do studies over a longer period to see whether the decrease in appetite and food intake we have seen translate into weight loss.
"If this passes clinical trials, it will not be a 'wonder treatment'. People will not be able to continue eating high-fat foods and drinking beer, hoping that this hormone would help them to lose weight. PYY3-36 would only be useful if used in addition to lifestyle changes."
A preliminary trial involving 12 obese and 12 lean volunteers revealed that the more obese the participant, the lower their level of the hormone. This could explain why obese people might not feel full after eating.
However, both the lean and the obese participants said they had felt less hungry on the day they were given the treatment, through 90-minute intravenous infusions. Control experiments were carried out using saline solution, and two hours after treatments, all participants were offered an unlimited buffet meal.
Dr Batterham said: "The greatest effect of hormone treatment was also seen in the most obese patient."
The NHS already offers patients two drugs for obesity, one that changes the way the stomach and gut absorb fat, and another which alters chemical processes in the brain to suppress appetite. But these can have side effects - for instance, the brain drug might raise blood pressure.
A few obese patients undergo stomach surgery as a last resort, but the search continues for a cost-effective way of tackling the condition. Any alternative may mean huge expense for the NHS. At present prices, hormone jabs would cost about 10 times £2-a-time insulin injections, and be far more expensive than existing drugs.
Dr Batterham said: "If all goes well, it could take five years until it is used as a treatment... There is also evidence to suggest that high-fibre diets may stimulate the release of the PYY3-36. Our future research will try to determine what controls the release of the hormone. If a food component turns out to have the same effect, it could be a far cheaper way of controlling the problem of obesity."
Ian Campbell, the chairman of the National Obesity Forum, said lifestyle changes had to be the priority, although he welcomed any development of better drugs. "I'm conscious we have been here before, and other 'wonder molecules' have failed to deliver," he said.
Three-fifths of Britons are overweight, and 21% clinically obese, he added. "That's a lot of people, far more than we can afford to treat with drugs."
