Researchers interested in developing drugs to treat obesity have turned their attention to brown fat, hoping to strike gold. Here’s why this metabolically-active form of fat has gotten their interest, and how you can make sure your own brown fat is working optimally.

First, brown fat is unique. Its primary function is to generate heat, a process called thermogenesis. It does this by burning fatty acids and sugar, just as is done in cellular energy metabolism. But instead of producing energy, brown fat has an “uncoupling” protein that shunts the process to the pathway of heat production. Brown fat helps to maintain normal body temperatures. It also “revs up” in a cold environment, to help you stay warm. Thin people have more brown fat than overweight people, and young people have more than older people.

There is still much to learn about brown-fat thermogenesis, but one fact is that the process requires T3, the active form of thyroid hormone. In fact, brown fat has a high concentration of the enzyme that converts T4, the inactive form, to T3. Much of the T3 in brown fat is converted directly in the tissue itself.

Unfortunately, some people have problems converting T4 to T3. Some factors that can impair T4 to T3 conversion include physical, mental, or emotional stress, as well as toxins. Taking supplemental T4 (as Synthroid) can also suppress T4 to T3 conversion. In any case, inadequate T3 can lead to a slow metabolism and obesity, cold intolerance, and sluggishness.

If these symptoms are all too familiar to you, here’s a way to find out if your metabolism is low: Take your body temperature. (For instructions on how to do this correctly, see “How are body temperatures measured” on our website.) If your body temperature is consistently low—below 98.5 F., or 36.94 C, but typically lower than 97.8 F, or 36.56 C.— there’s a good chance that you have a slow metabolism. It may mean that you are not converting enough T4 to T3. Proper body temperature is not only important to feel warm, but also because every process in your body— from energy metabolism to tissue repair—is affected by your body temperature.

I have found that people with low body temperature can improve dramatically if they get supplement thyroid hormone in the form of T3. This is the case even if they have normal blood levels of Thyroid Stimulating Hormone (TSH) or have been taking T4 (Synthroid.) Normalizing body temperature with T3 can improve mood, energy level, ability to drop excess weight, and a host of physical symptoms.

If you believe you might benefit from this therapy, share this article with your doctor, who can call us at 800.420.5801 to get more information about how to use T3, along with nutritional and herbs to support thyroid health, and to discuss your individual case. You can also use our website to find the health care practitioner closest to you who is trained in T3 treatment.

Bianco, AC & McAnich, EA. The role of thyroid hormone and brown adipose tissue in energy homoeostasis. The Lancet Diabetes and Endocrinology v. 1 n. 3 (Nov. 2013) pp. 250-8.

Lahesmaa M, Orava J, Schalin-Jäntti C, et al. Hyperthyroidism increases brown fat metabolism in humans. J Clin Endocrinol Metab. 2014 Jan;99(1):E28-35.

Obregon MJ. Adipose tissues and thyroid hormones. Front Physiol. 2014 Dec 11;5:479.

van Marken Lichtenbelt WD & Schrauwen P. Implications of nonshivering thermogenesis for energy balance regulation in humans. Am J Physiol Regul Integr Comp Physiol. 2011 Aug;301(2):R285-96.