The drug is the chemical cousin of an extract in red wine
French scientists say they have found a drug that tricks the body into burning off fat even when on a high-fat diet.
The University of Louis Pasteur team found the drug protected mice against weight gain and insulin resistance.
The drug SRT1720 - a chemical cousin of red wine extract resveratrol - targets the protein SIRT1, which is thought to combat ageing, Cell Metabolism reports.
UK obesity experts said new drug treatments were needed but should be used alongside lifestyle changes.
About a quarter of men and a third of women in the UK are overweight, according to government statistics.
A change in diet and an increase in physical exercise can shift excess weight, but can be hard for many to maintain.
With the removal of the anti-obesity pill rimonabant, also known as Acomplia, from the market amid safety concerns, fewer drug options exist.
The French team from the University Louis Pasteur became interested in the SIRT1 protein after earlier studies showing resveratrol countered some effects of a high-calorie diet via SIRT1.
But tests in mice suggested gallons of wine would be necessary for humans to stand a chance of getting the same benefits.
The scientists turned their attention to creating a more potent drug that would specifically target SIRT1.
They found that a low dose of SRT1720 partially protected mice from gaining weight on a high-fat diet after 10 weeks of treatment.
The drug worked by shifting the metabolism to a fat-burning mode that normally takes over only when energy levels are low.
At higher doses, the drug completely prevented weight gain. It also improved the rodents' blood sugar tolerance and insulin sensitivity, which are important for warding off diabetes.
The mice showed no sign of side effects. However, the scientists say further studies are needed to test the drug's safety and efficacy before it could be used in humans.
Other scientists are investigating SIRT1 activators similar to SRT1720 developed by Sirtris Pharmaceuticals.
Professor Stephen Bloom, who has been researching obesity at Imperial College London, said: "This sounds interesting but is terribly early.
"We do need new treatments for obesity, particularly as there are 1,000 deaths a week in the UK from obesity."
Prof Ian Broom, of the Centre for Obesity Research and Epidemiology at The Robert Gordon University, said: "Research in this area is to be welcomed as an additional route of combating the obesity epidemic and associated comorbid disease."
He added that any such drug should be used alongside dietary and lifestyle changes to tackle obesity.