NEW YORK -- The discovery of a "fat switch" in cells that controls fat production may lead to new ways to fight obesity -- but this will take time, researchers warn.

The production of fat is regulated at the cellular level by a family of proteins call Wnt, the investigators report in the August 11th issue of the journal Science.

"In earlier research, it was shown that lithium chloride inhibited fat cell development. It was then that researchers proposed that the lithium chloride may be mimicking the Wnt protein," according to researcher Dr. Ormond A. MacDougald of the University of Michigan Medical School in Ann Arbor.

"Our study is the first to suggest that Wnt, specifically Wnt-10b, is involved in the development of fat cells," he noted.

Studying mice, the research team found that fat cells with high levels of Wnt-10b stayed trim, while cells that lacked the protein became flabby.

"We learned a number of things that shed light on the production of fat cells," MacDougald told Reuters Health in an interview. "We discovered that overexpression (overproduction) of Wnt-10b blocks the development of fat cells and that the level of Wnt-10b falls off or decreases during the development of fat cells," he added.

"Wnt also plays a role in the development of muscle cells," MacDougald said. "At the stage just before a cell becomes a muscle cell, we inhibited Wnt and found that when we did that, the muscle cell turned into fat cell."

While MacDougald believes that the discovery "may help us understand how obesity occurs," he cautions that researchers still do not understand how the Wnt-10b protein is regulated in the cell. And he notes that most obesity today is caused by an increase in the fat cell size, not in the formation of new fat cells.

"It will be interesting to determine if its expression is altered in people who are obese or as we get older for instance," he added.