Thermogenesis

Thermogenesis is the production of heat by metabolic processes in the body. Metabolism continually releases energy as heat, and heat production contributes to maintaining body temperature, particularly when environmental conditions increase heat loss .^1,2

Heat production can increase through several mechanisms. Shivering thermogenesis results from involuntary contractions of skeletal muscles and can substantially increase metabolic heat production during cold exposure. Nonshivering thermogenesis produces additional heat without shivering and can involve metabolically active tissues such as brown adipose tissue .^1,3

Brown adipose tissue is specialized for heat production and contributes to nonshivering thermogenesis. Its mitochondria contain uncoupling protein 1, or UCP1, which uncouples fuel oxidation from ATP production, allowing more of the available energy to be dissipated as heat. Thermogenesis is broader than brown-fat activity, however, because heat can be produced through several tissues and physiological mechanisms .^1,3

Thermogenesis can also refer to the increase in energy expenditure that follows eating, called the thermic effect of food or diet-induced thermogenesis. This reflects energy expended in processes involved in the digestion, absorption, metabolism, and storage of nutrients. Thermogenesis is therefore a broad term for heat production, whereas shivering, nonshivering, adaptive, and diet-induced thermogenesis describe particular mechanisms or contexts of heat production .^1,2