Continuing coverage: While white fat is mainly used to store energy, brown fat keeps the body warm by burning calories once it is activated. Even better, brown fat seems to primarily "pick" those calories that come from fat and sugar, said Labros Sidossis, a professor of internal medicine in the division of geriatric medicine at UTMB. This in turn may be particularly helpful in fighting health issues such as diabetes and being overweight. "If you can activate it [brown fat], it can help you burn calories," Sidossis said.