Brown fat good, white fat bad

Not all fat is created equal. Biologists have known for years that babies have lots of brown fat but they thought it diminished with adulthood.


Unlike white fat cells, which are large oily droplets, brown cells consist of many small droplets. Brown fat gets its colour from energy cells called mitochondria reports Melinda Moyer in Scientific American.

Brown fat is important for babies because they can’t shiver when they are cold to generate heat.  Instead, the brown fat cells around their neck and shoulders generate heat: the brown fat metabolizes to keep baby warm and in doing so burns calories.

While baby fat visibly fades in adults, researchers have found that pockets of brown fat. This is encouraging news for those of us who would like to lose weight.

Brown fat cells burn more easily than white cells. And they act as kindling to metabolize white fat cells.

Taking a cue from babies, there is a way of firing up the brown fat cells but it’s not very pleasant. In one study, six men were kept inactive while wearing a cold suit that lowered skin temperature to 18 degrees C. That was cold enough to trigger brown fat cells but not enough to start shivering.

The six volunteers burned an extra 250 calories compared to what they would have burned at normal room temperature. That may not seem like much but if they burned 250 calories a day for two weeks, that would be enough to lose a pound of fat, all other factors remaining the same. Physiologist Barbara Cannon says: “Even very modest increases in metabolism over a long period of time can lead to significant weight reduction.”

Sitting around while losing weight has a lot of appeal. If such a claim were made now, it would seem preposterous;  just another crackpot ad.

But while sitting in the cold is a little off-putting, researchers are looking into the “browning” of white fat to make them easier to burn. Studies have found that a hormone produced by muscles after exercising makes white fat behave like brown fat; so-called “beige fat”. Mice lost weight when injected with a gene that tripled the amount of the hormone.

However, brown fat is still better at increasing metabolism and losing weight. Another study found that brown fat released five times more energy than beige fat.

Brown fat has more to offer than just weight loss. A study involving mice indicated that brown fat draws triglycerides out of the bloodstream. Those fatty molecules are known to contribute to metabolic syndrome: increased heart disease, stroke and diabetes.

Brown fat also draws sugar out of the bloodstream –sugar that contributes to high blood glucose that wreaks havoc with our body’s ability to manage sugar levels in the first place.

The key to good health would be to keep more of our baby brown fat. But don’t look for ads for brown fat anytime soon, claiming: “Keep fat, keep healthy.” The best way of burning brown and white fat is still exercise.


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