SCIENTISTS have created an exercise pill that tricks cells into thinking they are undergoing serious exertion and so helps the body burn extra fat.

The drug hints at radical new potential treatments for obesity where fat people would be able to use drugs to slim down rather than dieting or exercising.

The drug, a synthetic form of fat, is purely experimental and has so far only been tested on animals. It appears to work by flicking a master switch within cells that regulates the laying down or burning of fat.

Dr Ronald Evans, the researcher who created the drug, will tell scientists at the Experimental Biology conference in Washington DC this weekend that such drugs could lead to new treatments for human metabolic syndrome.

Sometimes called syndrome X, this consists of obesity and its consequences such as high blood pressure, elevated levels of fat in the blood, heart disease, diabetes and resistance to insulin.

It comes as obesity levels in Britain reach unprecedented levels with about two-thirds of adults classed as overweight and a fifth as obese. More than 10% of the National Health Service’s hospital budget is spent on treating diabetes.

Evans, of the Salk Institute, in San Diego, California, found the drug activated the same fat-burning process that occurs during exercise, increasing the amount of calories burnt with no apparent effort. This made the mice resistant to weight gain even on a high-fat diet.

Evans is renowned for his research into obesity. He discovered how to control the so-called PPARd (peroxisome proliferator-activated receptor, delta) switch, the master regulator of fat metabolism in cells.

He used genetic engineering to create a strain of mice that had an innate resistance to weight gain and had twice the physical endurance of normal mice. Their ability to run an hour longer than a normal mouse led to them being dubbed the “marathon mice”.

Such discoveries did not, however, lead to potential new treatments because the genetic engineering that created the marathon mice had to be carried out before birth and would be unacceptable for humans.

“That is why the potential of chemical metabolic engineering — possibly a one-a-day pill as opposed to permanent genetic metabolic engineering — is so exciting, said Evans. “In today’s society too few people get an ideal amount of exercise; some because of medical problems or excess weight that makes exercise difficult.”

Such a drug could, he suggests, reduce fatty tissue, lower amounts of fat circulating in the blood, cut blood glucose levels and reduce resistance to insulin, limiting the risks of heart disease and diabetes.

More than 1.9m people in the UK are diagnosed with type 2 diabetes and up to 750,000 more are thought to be undiagnosed. Type 2 is linked to obesity, and experts believe up to half of all cases could be prevented through changes to diet and exercise.

There are already a range of antifat drugs on the market, but they are criticised by nutrition researchers. They point out that people who take such drugs may lose weight at first but then pile it back on soon after.

“These drugs may work in the laboratory, but they always fail in the real world,” said Marion Nestle, professor of nutrition at New York University, and author of What to Eat, a book on diet. “If people want to get thin they have to control the calories they consume and exercise more.”

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