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Identify the body's fuel source as its metabolic pathways shift from feasting to fasting. Glycogen stores Body fat stores Body protein Fuel for the body 2 to 3 hours after eating Fuel for the body after 24 hours of starvation Fuel for the brain 2 to 3 hours after eating Fuel for the brain after 24 hours of starvation O
Identify the body's fuel source as its metabolic pathways shift from feasting to fasting. Glycogen stores Body fat stores Body protein Fuel for the body 2 to 3 hours after eating Fuel for the body after 24 hours of starvation Fuel for the brain 2 to 3 hours after eating Fuel for the brain after 24 hours of starvation O
Final answer:During feasting, glucose is the main fuel while proteins and fats are stored. Postprandial, glycogen is used for energy, shifting to body fat stores as glycogen depletes. During prolonged fasting or starvation, the body uses ketone bodies, preserving muscle protein and utilizing it as a last resort.Explanation:Body's Fuel Source during Feasting and FastingDuring the absorptive or feasting state, the body primarily uses glucose from ingested food for energy. Proteins and fats consumed are also processed and stored.In the postabsorptive (fasting) state, initially, glucose continues to be the main source of energy, derived from glycogen stores in the liver and muscle tissues. After 2 to 3 hours, these stores start to deplete, and the body begins to transition into utilizing body fat stores for energy production.After 24 hours of fasting evolving into starvation, the body increases reliance on ketone bodies derived from fatty acids as the primary energy source. The brain, however, continues to require glucose, which is supplied through gluconeogenesis predominantly from breakdown of protein when other sources are not sufficient.If fasting persists and starvation intensifies beyond the first few days, the body's metabolism adapts by conserving muscle tissue and increasingly using ketone bodies for energy. Proteins in organs with a fast turnover, such as the intestinal lining, are catabolized first. The brain starts utilizing ketone bodies, reducing the need for glucose and sparing muscle protein. Eventually, without breaking the fast, essential protein from muscles can be consumed as a last resort when all other stores have been exhausted....