Washington, July 2: Scientists reported yesterday that they have uncovered a biological switch by which stress can promote obesity, a discovery that could help explain the world’s growing weight problem and lead to new ways to melt flab and manipulate fat for cosmetic purposes.

In a series of experiments on mice, researchers showed that the neurochemical pathway they identified promotes fat growth in chronically stressed animals that eat the equivalent of a junk-food diet.

The international team also showed that blocking those signals can prevent fat accumulation and shrink fat deposits and that stimulating the pathway can strategically create new deposits — possibly offering new ways to remove fat as well as to mould youthful faces, firmer buttocks and bigger breasts.

“It’s very exciting,” said Zofia Zukowska of Georgetown University’s department of physiology and biophysics, who led the research, published online by the journal Nature Medicine. “This could be revolutionary.”

While cautioning that the safety and effectiveness of the approach remain to be proven in people, other researchers said the findings reveal new clues about the basic biology of fat and why obesity has been increasing so quickly, particularly in western countries.

“There is a lot of uncontrollable stress right now in our societies. There’s also a lot of inexpensive high-fat food,” said Mary F. Dallman of the University of California at San Francisco, who co-wrote a commentary accompanying the research. “This could help explain the obesity epidemic.”

The researchers have applied for a patent and have begun negotiating with drug companies to licence the technology. They predicted that studies in people could begin within two years. Previous studies have indicated that whereas acute stress can make some people lose weight, chronic stress, such as long-term job insecurity, might cause some to put on pounds.

To explore this, Zukowska and her colleagues subjected mice to chronic stress — either standing in cold water an hour a day or being caged with a more aggressive alpha mouse for 10 minutes a day — and then gave them standard feed or a high-fat, high-sugar diet similar to the junk-food fare many consume.