A GlaxoSmithKline drug being developed to treat high cholesterol levels has been shown to reduce weight gain in mice dramatically when they are fed a high-fat diet.

The results from an independent study by scientists at California's Salk Institute indicate that the drug will be investigated as a treatment for obesity by the British drugs company.

The drug, GW501516, is in mid-stage clinical trials to treat dyslipidaemia, a disorder of cholesterol levels. It is years away from sale, and potential side-effects of increasing cancer risk and oedema (fluid build-up) need to be looked at.

But Glaxo said the research is "very interesting" and will now review the study and consider starting trials of the drug as a treatment for the overweight.

The obesity market is lucrative, particularly in the high-spending US, and is estimated to be worth $5bn (£2.8bn) in 2010 by investment bank Lehman Brothers. Obesity drugs are being developed by numerous pharmaceuticals companies, including Sanofi and UK biotech Alizyme, as well as GlaxoSmithKline, which has already licensed a drug named Xenical that inhibits the absorption of fat in the gut.

"The area of metabolic syndrome, diabetes and obesity [is linked] and whoever cracks that will make a lot of money," said Stewart Adkins, an analyst at Lehman Brothers.

In the scientific study, which was published in the journal Public Library of Science Biology, 10 mice were fed a high-fat diet for 60 days. Half were given the drug, the other half used as a control.

The mice given the drug only gained 4g of weight on average compared with a normal mouse, which gained 12g. When given the drug, mice also appeared to develop a more athletic type of muscle, known as "type 1 fibre" that is linked to lower levels of fatigue, obesity and diabetes.

The effects of the drug were tested as a sideline to research into genetically engineered "marathon mice". These mice were made to run on treadmills until exhausted; the running time and distance they achieved were increased by 67% and 92% respectively.

These mice were genetically engineered to produce higher levels of the PPAR- (pronounced p-par) delta protein and had higher levels of the type 1 muscle.

The PPAR-delta protein is boosted by the GW501516 drug, and therefore the abilities of the transgenic mice might be mimicked by the drug.