Study May Lead to New Fat-Burning Drug

Ultimately, weight loss comes down to burning more calories than you take in. This can be achieved by either reducing extra calories from food and beverages, increasing physical activity, or ideally, doing both. Losing one pound requires an expenditure of about 3,500 calories. That means, for example, eating 500 fewer calories—one less quarter-pound hamburger with cheese—each day for a week, or burning an additional 500 calories through exercise—about 1.5 hours of brisk walking—per day for a week. But a recent discovery may one day make it a little easier to achieve a leaner physique.

Researchers at Albert Einstein College of Medicine and Neuroscience in New York say they have found a way to trick the body into burning extra fat—in mice, at least! In a laboratory test, mice treated with a compound to block an enzyme called Fyn kinase displayed not only significant weight loss but also an increase in energy expenditure. The new findings build on the team’s previous research showing that mice lacking the enzyme burn more fatty acids and were leaner than their normal littermates. The enzyme-deficient mice also showed other metabolic improvements, including increased insulin sensitivity.

First the mice were given 48 hours to become accustomed to a metabolic chamber, which allows researchers to monitor energy intake and expenditure. Both groups showed identical carbohydrate use during the dark cycle (when they are most active) prior to treatment. Then, at the beginning of the light cycle, when the animals are least active, one group was injected with an experimental compound known as SU6656 that blocks Fyn kinase, while the control group received an inert substance.

After injection, the control mice reduced energy use as their bodies switched to normal lipid production. On the other hand, the treated animals continued to expend energy at a significantly higher rate than the controls, although there was no measurable difference in physical activity. Both groups experienced a slight reduction in lean mass, but the SU6656-treated mice had a significant reduction in fat mass. Overall, the treated mice had a 40 percent greater weight loss than the control group and a 14 percent increase in energy expenditure.

Obesity occurs “when there is an imbalance between what we eat and what we burn,” and the problem is not going away, said study lead Dr. Claire Bastie. “This is a new mechanism to help the body to burn extra energy.” Bastie cautions that more research is needed to find a compound that can block Fyn kinase safely in humans. Because the enzyme has effects in the brain as well as muscle and fat tissue, scientists would need to develop a drug that targets only the molecular players they want it to. “Our next goal is to design something extremely specific to muscle and adipose,” she said.