Injections of a gut hormone that tells the brain the stomach is full resulted in significant weight loss in a small human test, British researchers report in today’s issue of the journal Diabetes.

The study lasted a month and included 14 subjects. They lost an average of about 5 pounds, reported Dr. Stephen R. Bloom, an endocrinologist at Imperial College London.

Despite the short trial length, he said, the hormone – called oxyntomodulin – is promising because it appears to lack the side effects seen in other anti-obesity drugs.

The most widely used drug, Meridia, for example, affects brain chemistry and can produce not only mild side effects such as dry mouth and constipation, but more serious ones such as high blood pressure and an increased heart rate.

None of those effects were observed in the test of oxyntomodulin.

Bloom said the hormone still needed to be tested in more patients and for longer periods. He said he also needed to find a way to circumvent the need to inject the hormone three times a day.

Oxyntomodulin is naturally produced in the human intestine and is released when the stomach becomes full.