Thermogenesis is the process by which the body generates heat. The body’s thermogenic actions are usually classified as obligatory (OT) or facultative (FT, also known as adaptive thermogenesis). OT represents all the life-promoting activities in your body that transform energy into heat, such as the burning of calories. FT refers to body actions that kick in to generate heat when the body gets too cold, such as shivering.

Thyroid hormones influence oxygen consumption and enzyme function in a way that raises metabolism and triggers heat production – unleashing a powerful thermogenic effect. For nearly a century, we’ve known that thyroid hormones influence OT. But more recent research has suggested that thyroid hormones may also influence FT – and in doing so, may hold promise for treating obesity.

Brown adipose tissue, also known as brown fat, is very important for FT in humans and all mammals. Brown fat is stored energy, capable of generating heat as an adaptive (FT) response to cold. Researchers have suggested that T3 concentration in brown fat tissues is responsible for the peak thermogenic response to adrenal stimulation. In other words, T3 is believed to directly trigger the burning of brown fat for heat generation as an adaptive response to cold exposure.

Researchers have suggested that if we could ever isolate T3’s direct brown fat burning influence as a standalone mechanism, it could be used as a novel way to treat overweight and obesity.