Researchers have found a form of fat that actually burns calories, rather than storing them.
During exercise a hormone converts regular fat cells into "beige fat" cells, which burn up extra calories.
Researchers at Dana-Farber Cancer Institute are studying the fat, hoping they can figure out how to harness it's calorie-burning properties with new drugs.
The experts say they are still in the early stages of their research. Many more studies will be needed before any therapies are made available.