How to Burn Off Blubber Without Moving a Muscle

FLICKING a metabolic switch could help obese people burn off excess fat, say researchers in Italy. Saverio Cinti and his colleagues at the University of Ancona have managed to transform normal fat cells in rats into a different type that burns energy to produce heat, instead of storing it. They hope that similar drugs could be developed to help people lose weight.
Body fat, or adipose tissue, is actually a complex organ, composed of two different types of fat cell. White adipose tissue mainly stores fat. Brown adipose tissue, however, keeps the body warm by releasing the energy stored in fat as heat.

The ratio of white to brown fat is influenced by the environment. People who work outdoors in cold climates have more brown fat. What's more, if you keep a rat at 4 °C for a few days, it develops more brown fat, Cinti told the joint meeting of the Association for the Study of Obesity and the Nutrition Society in London last week. Once a rat is returned to normal temperatures, the effect is reversed.

Scientists have long known that drugs called beta-3 adrenoreceptor agonists can alter the ratio of fat cells, but thought new brown fat cells might be replacing existing white fat cells. Now Cinti and his colleagues have shown that a beta-3 agonist called CL 316243 actually transforms mature white fat cells into brown fat cells--a remarkable example of cell plasticity.

In rats given CL 316243, Cinti found that the white cells took on the appearance of brown cells and developed many more mitochondria, the powerhouses of cells. What's more, they also started to make a protein called UCP-1.

In most cells, mitochondria use the energy they liberate to make ATP, the fuel that drives chemical reactions in living organisms. But in brown fat cells, UCP-1 "uncouples" this process, forcing the cells to release energy as heat.

Previous studies have shown that beta-3 agonists can help obese mice to lose weight. There's no reason why the approach should not work in humans, Cinti says. "Potentially, the adipose organ of all humans has the possibility of transforming into brown fat." However, a treatment for people is some way off, he adds, as no one has yet developed a safe drug.

One problem is that the beta-3 receptors of rodents have a very different structure to those of humans. Drugs companies are now trying to develop compounds that activate the human receptor, says Steve Smith of SmithKline Beecham. "The beauty of beta-3 agonists is that all the weight loss occurs from fat and not muscle."

Stephanie Oakes is a fitness correspondent for Discovery Health Channel, a contributing editor for USA Weekend Magazine and the LA Times, and appears on NBC's 'Today in New York'. She can be reached at soakes@beststuff.com.

Congratulations to our own Health /Fitness Expert Stephanie Oakes. Stephanie now represents BestStuff.com as the new Fitness columnist for USA Today's Weekend Magazine. USA Weekend is in 560 newspapers with more than 42 million readers every Sunday.