<P> 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 . </P> <P> Starvation contributes to tolerance during infection, as nutrients become limited when they are sequestered by host defenses and consumed by proliferating bacteria . One of the most important causes of starvation induced tolerance in vivo is biofilm growth, which occurs in many chronic infections . Starvation in biofilms is due to nutrient consumption by cells located on the periphery of biofilm clusters and by reduced diffusion of substrates through the biofilm . Biofilm bacteria shows extreme tolerance to almost all antibiotic classes, and supplying limiting substrates can restore sensitivity . </P> <P> Starvation mode is a state in which the body responds to prolonged periods of low energy intake . During short periods of energy abstinence, the human body burns primarily free fatty acids from body fat stores, along with small amounts of muscle tissue to provide required glucose for the brain . After prolonged periods of starvation the body has depleted its body fat and begins to burn primarily lean tissue and muscle as a fuel source . </P> <P> Ordinarily, the body responds to reduced energy intake by burning fat reserves and consuming muscle and other tissues . Specifically, the body burns fat after first exhausting the contents of the digestive tract along with glycogen reserves stored in liver cells . After prolonged periods of starvation, the body uses the proteins within muscle tissue as a fuel source . </P>

Where does body get energy from when fasting