thermogen

Thermogen, in physiology and pharmacology, describes anything that increases heat production in living organisms. The term encompasses natural thermogenesis—the body's generation of heat through metabolic processes—and thermogenic compounds that stimulate these processes.

Physiological bases include non-shivering thermogenesis, which occurs primarily in brown adipose tissue (BAT) via the mitochondrial protein UCP1, which uncouples oxidative phosphorylation to release energy as heat. Beige adipocytes can arise in white adipose tissue and contribute to thermogenesis. The sympathetic nervous system, through norepinephrine, activates BAT and browning of white fat. Thyroid hormones increase the overall metabolic rate. Diet-induced thermogenesis accounts for energy expenditure associated with digestion, absorption, and processing of nutrients, while exercise-induced thermogenesis reflects heat production from muscular activity.

Thermogenic agents refer to substances that promote heat production and may be used to influence energy expenditure. Commonly studied exogenous thermogens include caffeine, capsaicin and related capsaicinoids, catechins such as EGCG from green tea, and various combinations marketed as dietary supplements. Other stimulants such as ephedrine have been used historically but are restricted or banned in many jurisdictions due to safety concerns.

Effectiveness and safety considerations vary. Experimental results show small increases in energy expenditure, with effects differing among individuals and potentially diminishing over time due to tolerance. Thermogenic claims should be evaluated critically, and products containing stimulant ingredients may carry cardiovascular or other health risks, underscoring the importance of regulatory guidance and cautious use.

Thermogenesis is a broad area of physiology with relevance to metabolism and energy balance.