thermogenesis

n.
Generation or production of heat, especially by physiological processes.

thermogenetic ther'mo·ge·net'ic (-jə-nĕt'ĭk) or ther'mo·gen'ic (-jĕn'ĭk) adj.

Increased heat production by the body, either to maintain body temperature (by shivering or non-shivering thermogenesis) or in response to food intake, diet-induced thermogenesis. See also brown adipose tissue.

The production of heat energy. Chemical reactions in the body generate heat, increasing with higher levels of activity. Getting rid of the heat can be a problem when exercising intensely, especially in warm, humid environments. In cold environments, extra heat may be generated by shivering (‘shivering thermogenesis’) or by metabolism of special fat cells (‘non-shivering thermogenesis’; see brown fat). See also diet induced thermogenesis.

The production of body heat. Most body heat is a by-product of metabolism. These reactions increase during exercise, consequently there is a greater risk of overhearing. During cold weather, extra internal heat may be generated by increasing metabolism (non-shivering thermogenesis), and by uncontrolled muscular contractions (shivering thermogenesis). Non-shivering thermogenesis involves stimulation of metabolism by the sympathetic nervous system. See also thermic effect of food.

The production of heat, especially within the animal body.

• diet-induced t. — a portion of dietary calories in excess of those required for immediate energy requirements are converted to heat rather than stored as fat. Some types of obesity may be related to a defect in this mechanism.
• neonatal t. — thermogenesis is relatively inefficient in neonates, especially piglets, so that it becomes very important to protect them from cold stress. Most of their heat gain comes from the metabolism of their stores of brown fat.
• nonshivering t. — increased heat production due to enhancement of normal calorigenic metabolic processes.
• shivering t. — much the fastest thermogenic process which the static body can use. Shivering is an involuntary function with a tremor rate of about 10 per second.

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