Exercise Can Turn Bad Fat (White Fat) Into Good Fat (Brown Fat)

Researchers have found that exercise helps "bad" fat transform into a form of "good" fat that is more metabolically active.

The findings were presented at the American Diabetes Association's 73rd Scientific Sessions. Humans have two types of fat: 1. Brown fat (the good fat) - this type of fat burns through calories to generate body heat. 2. White fat (the bad fat) - this fat develops as a result of storing excess calories, it is just an energy reserve.

People with more brown fat are generally slimmer and better able to stay warm when it is cold, whereas individuals who have high levels of white fat tend to live more sedentary lifestyles. In this study, the researchers found that mice and men who underwent an intense exercise regime experienced a browning of their subcutaneous white adipose tissue (SCWAT). The exercise regime had the men training on an exercise bicycle for 12 weeks and the mice running on an exercise wheel for 11 days. Compared to the original white fat caused by sedentary behavior, the new, browner fat, was much more metabolically active.

The researchers transplanted this trained browner fat into sedentary fat mice to see how the browner fat might affect the way their bodies use glucose. They found that after the transplant the mice had increased glucose tolerance and insulin sensitivity for at least 3 months. Kristin Stanford, PhD, a postdoctoral fellow at Joslin Diabetes Center in Boston, said: "Our results showed that exercise doesn't just have beneficial effects on muscle, it also affects fat. It's clear that when fat gets trained, it becomes browner and more metabolically active. We think there are factors being released into the bloodstream from the healthier fat that are working on other tissues." It is still uncertain whether browner fat is having the same impact on humans as there is currently no way to try out fat transplantation on human beings.

Senior investigator of one of the studies, Laurie Goodyear, PhD, and associate professor at Harvard Medical School, said: "We know that exercise is good for us. But what we're showing here is that fat changes dramatically in response to exercise training and is having good metabolic effects. This is not the fat that's around your middle, which is bad fat and can lead to diabetes and other insulin resistant conditions. It's the fat that's under the skin, the subcutaneous fat that adapts in a way that appears to be having important metabolic effects." In conclusion the study reveals that browner fat is associated with a better body composition, lower fat mass and increased glucose uptake and insulin sensitivity in mice. Stanford says the findings provide even more motivation to go out and start exercising. Even if you don't lost weight, the study suggests that exercising will still train your fat to be more metabolically active and improve overall metabolism and health.