An obese boy exercises in Beijing. (AFP)

London, July 25 (Reuters): British scientists said today they had developed a new treatment that could help obese and overweight people lose weight by making them feel full.

Researchers at Imperial College London believe the treatment, an injection of a natural digestive hormone called oxyntomodulin that is released in the small intestine, could help to stem the world’s growing obesity epidemic.

“The discovery that oxyntomodulin can be effective in reducing weight could be an important step in tackling the rising levels of obesity in society,” said Prof. Steve Bloom, who headed the research team.

The injection switches off the appetite so people eat less.

In a four-week trial of 26 people, volunteers who were given three injections of the treatment each day 30 minutes before meals lost an average of 2.3 kg. A control group that had dummy injections lost about half a kg.

Patients had no side effects from the treatment. “It is just fooling the brain that you have already had lunch by releasing the appetite hormone before you have actually eaten,” Bloom explained in an interview.

He and his colleagues, who reported their findings in the journal Diabetes, said it was still early days and more research needed to be done. But they have already set up a company called Thiakis to develop the treatment, which they hope will be available by prescription in about five years.

They initially envision it as a treatment for people who are overweight or obese and have a medical problem. But once it is established it could be rolled out more widely. More than a billion adults worldwide are overweight and at least 300 million of them are obese. By 2025, the number could soar to 333 million, according to the WHO.

Being overweight or obese is calculated by using the body mass index (BMI) ? dividing weight in kilograms by height in metres squared. A BMI of more than 25 is overweight. Above 30 is considered obese.

Excessive weight is a risk factor for diabetes, cardiovascular disease, osteoarthritis and other illnesses. Researchers have shown that treating obesity-related disorders costs as much or more than treating illnesses caused by ageing, smoking and problem drinkers.

Bloom and his colleagues have developed a once-a-day injection and are looking into delivering the treatment through a nasal spray.

”When it comes to taking a pill with water or taking a disposable syringe with a super-fine needle and pressing the plunger, it really isn't very difficult,” Bloom said.

Patients given the injection also had reduced levels of leptin, a protein responsible for regulating the body's energy expenditure. They also had lower amount of adipose hormones that encourage the build-up of adipose tissue ? where fat cells are stored in the body.