Brown Adipose Tissue: The Body’s «Calorie-Burning Powerhouse»

When we hear the word 'fat', we often think of stored energy and extra weight. But there is a type of fat that does the exact opposite: it burns calories to produce heat. This is brown adipose tissue (BAT)! For decades, it was believed that BAT existed only in infants, but science has revealed that brown adipose tissue continues to be present in adults as well.

What is brown adipose tissue?

Unlike white adipose tissue, which serves as an energy reservoir, brown adipose tissue acts like a thermogenic powerhouse. Its cells contain abundant mitochondria—the tiny energy-producing organelles—and high amounts of iron, giving the tissue its characteristic brown color. Its main mission is to generate heat (without causing shivering), helping the body maintain its temperature, especially in newborns or during exposure to cold environments.

How is brown adipose tissue activated?

The primary "switch" that turns on brown adipose tissue is exposure to cold. When environmental temperatures drop, the brain sends signals through the nervous system, triggering the release of a substance called noradrenaline. This "wakes up" brown fat cells and drives them to ramp up their activity. Within their mitochondria, a special protein called UCP1 changes the way energy is processed. Instead of storing energy in the form of fuel (ATP), they burn it directly and release it as heat. This allows the body to use stored calories to stay warm without relying on muscle shivering.

Brown vs. White vs. Beige Fat

Not all fat tissue in the body is the same. There are three main types, each with distinct roles:

• White fat (WAT): The body's "storage unit." It accumulates excess energy in the form of fat for future use.

• Brown fat (BAT): The body's "calorie burner."

• Beige or "brite" fat: An intermediate type. These are white fat cells that, under certain conditions—such as prolonged exposure to cold, physical activity, or specific hormonal influences—can "transform" and behave like brown fat. This process is known as browning.

Why is brown adipose tissue so important?

Research has shown that individuals with greater amounts or activity of brown adipose tissue may enjoy significant metabolic benefits:

• They have higher calorie expenditure at rest.

• They display improved insulin sensitivity, lowering their risk of type 2 diabetes.

• They are partly protected from fat accumulation since excess energy is converted to heat instead of being stored.

How can we activate it?

Although research is still ongoing, several approaches appear to boost the activity of brown adipose tissue:

• Mild cold exposure: Spending time in environments of 17–19°C regularly can gradually increase BAT activation.

• Cryotherapy: A method where the body is exposed for about 3 minutes to extremely low temperatures (-100°C to -180°C) in a specialized chamber.

• Physical activity: Exercise stimulates the release of irisin, a hormone that can convert portions of white fat into beige fat.

Could brown adipose tissue be the “key” to weight loss?

The answer is that it can be a valuable ally, but it’s not a magic solution. With healthy habits, regular movement, and occasional exposure to cold, we can harness its natural ability to burn calories and enhance our overall well-being.

References

Jung, S. M., Sanchez-Gurmaches, J., & Guertin, D. A. (2019). Brown Adipose Tissue Development and Metabolism. Handbook of experimental pharmacology, 251, 3–36. https://doi.org/10.1007/164_2018_168

Cheng, L., Wang, J., Dai, H., Duan, Y., An, Y., Shi, L., Lv, Y., Li, H., Wang, C., Ma, Q., Li, Y., Li, P., Du, H., & Zhao, B. (2021). Brown and beige adipose tissue: a novel therapeutic strategy for obesity and type 2 diabetes mellitus. Adipocyte, 10(1), 48–65. https://doi.org/10.1080/21623945.2020.1870060 

Iwen, K. A., Backhaus, J., Cassens, M., Waltl, M., Hedesan, O. C., Merkel, M., Heeren, J., Sina, C., Rademacher, L., Windjäger, A., Haug, A. R., Kiefer, F. W., Lehnert, H., & Schmid, S. M. (2017). Cold-Induced Brown Adipose Tissue Activity Alters Plasma Fatty Acids and Improves Glucose Metabolism in Men. The Journal of clinical endocrinology and metabolism, 102(11), 4226–4234. https://doi.org/10.1210/jc.2017-01250

van der Lans, A. A., Hoeks, J., Brans, B., Vijgen, G. H., Visser, M. G., Vosselman, M. J., Hansen, J., Jörgensen, J. A., Wu, J., Mottaghy, F. M., Schrauwen, P., & van Marken Lichtenbelt, W. D. (2013). Cold acclimation recruits human brown fat and increases nonshivering thermogenesis. The Journal of clinical investigation, 123(8), 3395–3403. https://doi.org/10.1172/JCI68993

Huo, C., Song, Z., Yin, J., Zhu, Y., Miao, X., Qian, H., Wang, J., Ye, L., & Zhou, L. (2022). Effect of Acute Cold Exposure on Energy Metabolism and Activity of Brown Adipose Tissue in Humans: A Systematic Review and Meta-Analysis. Frontiers in physiology, 13, 917084. https://doi.org/10.3389/fphys.2022.917084

Chechi, K., van Marken Lichtenbelt, W., & Richard, D. (2018). Brown and beige adipose tissues: phenotype and metabolic potential in mice and men. Journal of applied physiology (Bethesda, Md. : 1985), 124(2), 482–496. https://doi.org/10.1152/japplphysiol.00021.2017

Herz, C. T., & Kiefer, F. W. (2019). Adipose tissue browning in mice and humans. The Journal of endocrinology, 241(3), R97–R109. https://doi.org/10.1530/JOE-18-0598

Lee, P., Werner, C. D., Kebebew, E., & Celi, F. S. (2014). Functional thermogenic beige adipogenesis is inducible in human neck fat. International journal of obesity (2005), 38(2), 170–176. https://doi.org/10.1038/ijo.2013.82

Singh, R., Barrios, A., Dirakvand, G., & Pervin, S. (2021). Human Brown Adipose Tissue and Metabolic Health: Potential for Therapeutic Avenues. Cells, 10(11), 3030. https://doi.org/10.3390/cells10113030

Mu, W. J., Zhu, J. Y., Chen, M., & Guo, L. (2021). Exercise-Mediated Browning of White Adipose Tissue: Its Significance, Mechanism and Effectiveness. International journal of molecular sciences, 22(21), 11512. https://doi.org/10.3390/ijms222111512