Injections of a gut hormone which switches off appetite helps overweight people lose pounds, a study has found.
The treatment could be another option for people who want to lose weight
A team from Imperial College say the four-week trial suggested oxyntomodulin - naturally found in the intestine - could be a new way of tackling obesity.
The research in Diabetes said those on the hormone lost an average of 2.3kg (5lbs) in four weeks, compared to 0.5kg (1lb) for those on a dummy treatment.
Experts said more studies were needed to confirm the hormone's benefits.
Oxyntomodulin is normally released from the small intestine as food is consumed.
It tells the brain not to eat any more at the end of a meal when the body has had enough to eat.
The researchers, from Imperial College and Hammersmith Hospitals NHS Trust, studied the effect of boosting people's oxyntomodulin levels.
The team looked at 26 people who were all overweight or obese.
Fourteen injected themselves with oxyntomodulin 30 minutes before each meal, three times a day, for four weeks.
Twelve administered saline at the same frequency for the same period.
Neither doctors nor patients knew which group they were in during the study.
In addition to seeing greater weight loss, the group taking oxyntomodulin also had a reduced appetite, but they saw no change in their enjoyment of food.
Levels of leptin, a protein known to be responsible for regulating the body's energy expenditure, and adipose hormones, which encourage the build up of a type of tissue where fat cells are stored, were also found to be lower in the group having hormone injections.
'Will not stop working'
Professor Steve Bloom, senior researcher at Imperial College London and Hammersmith Hospital, who led the study, told the BBC: "We saw a dramatic rate of weight loss."
He said the fact that it was natural gave oxyntomodulin an advantage over other treatments.
Professor Bloom, who has set up Thiakis, a company in order to continue developing the treatment, added: "You have your own oxyntomodulin every time you eat lunch or supper, so it's not quite like a drug.
"I would anticipate it being completely safe and also, since you have your own oxyntomodulin, it isn't likely to ever stop working."
He said that was a problem with existing anti-obesity drugs.
But Professor Bloom said larger trials were needed to check the treatment was effective over longer periods.
Dr Ian Campbell, president of the National Obesity Forum, said the study was exciting.
He added: "The weight-loss was significant, but questions need to be asked about what the weight loss would be with the additional lifestyle changes, and the efficacy over a period of time much longer than four weeks.
"But it's certainly worthy of further investment and research."