Starvation response in animals (including humans) is a set of adaptive biochemical and physiological changes, triggered by lack of food or extreme weight loss, in which the body seeks to conserve energy by reducing metabolic rate and/or non-resting energy expenditure to prolong survival and preserve body fat and lean mass.
Equivalent or closely related terms include famine response, starvation mode, famine mode, starvation resistance, starvation tolerance, adapted starvation, adaptive thermogenesis, fat adaptation, and metabolic adaptation.