by Lauren Fiechtner, MD

As mammals we have two different types of fat tissue: white and brown. White fat stores energy and plays a role in how full we feel. Brown fat helps regulate the body’s temperature by releasing heat. In mice brown fat has been linked to improved insulin sensitivity and decreased body weight. In humans brown fat has been associated with lower BMI. So we think brown fat is healthier and more efficient than white fat.
Recently Moisan and colleagues used human stem cells to study how white fat can become brown fat. They found two compounds – tofacitinib and R406 – to be powerful inducers of the pathway that coaxes this change. Tofacitinib is FDA approved to treat rheumatoid arthritis, so can’t we just start taking this pill to make our fat healthier? To target fat tissue, however, tofacitinib would need to be delivered directly to fat tissue.  And there are many steps that need to be taken before we can just take a pill to convert white into brown fat. Most importantly, the same concept needs to be studied in an actual human body as opposed to just stem cells.

Is there another way to convert your white fat to brown? In fact there is. A group from the NIH conducted a study that monitored 5 men sleeping in climate-controlled rooms at the NIH for four months. The first month, the bedrooms were kept at 75 degrees and the second month at 66 degrees. During the third month, they were put back to 75 degrees and, finally, in the fourth month the temperature was increased to 81 degrees. Sleeping at 66 degrees caused a near doubling of brown fat in participants. They also had improved insulin sensitivity and burned a few more calories per day. However, they did not lose any weight. 81 degrees had the opposite effect: the participants had less brown fat than at the beginning of the study.

Although these studies are just preliminary evidence, and we need larger human studies, increasing our brown fat may be beneficial. Perhaps tonight you should save money on your heating bill and improve your metabolism by turning down your thermostat!



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