More specifically, there are different types of fat that have different hues and functions, according to Talbott: white, brown, and beige. The white fat is what most people think of as fat—pale and useless. Useless in that it has a low metabolic rate so it doesn’t help you burn any calories the way muscle does, and it’s the predominant type of fat in the human body, encompassing more than 90 percent of it. In other words, it’s a storage unit for extra calories.
Brown fat is darker in color due to a rich blood supply and can actually burn calories rather than storing them—but only if you’re a rat (or other mammal); certain critters can activate brown fat to burn calories and generate heat to keep them warm in winter. Humans, sadly, have so little brown fat that it won’t help you burn calories or keep you warm.
The third type of fat, beige fat, is in between white and brown in terms of its calorie-burning ability, which is actually very exciting. Why? Because researchers are looking into ways to shift white fat cells into more metabolically active beige ones via diet and exercise or supplements. In fact, there is preliminary evidence that certain hormones which are activated by exercise may convert white fat cells into beige ones, as well as some evidence that certain foods such as brown seaweed, licorice root, and hot peppers may have the ability to do this as well.