Final answer:
During hunger and starvation, the body enters a state of catabolysis to maintain energy for vital functions, leading to loss of muscle and fat. Persistent starvation results in protein utilization and can cause death due to cardiac complications. The body's metabolism adapts by switching to ketogenic fat metabolism and altering hormone levels to manage glucose.
Step-by-step explanation:
During hunger and starvation, the body undergoes several metabolic changes to conserve energy and support vital functions. Early symptoms include irritability, impulsivity, and hyperactivity. The body begins catabolysis, breaking down its own muscles and tissues for energy, leading to muscle and fat loss. This adaptation initially helps to sustain the nervous system and other critical operations, despite the onset of apathy and fatigue as energy reserves wane.
As starvation persists, the body depletes its fat reserves and begins to utilize proteins, affecting the functionality of vital organs and potentially leading to death. Typically, death by starvation can be caused by cardiac arrhythmia or cardiac arrest due to tissue degradation and electrolyte imbalances. Factors like metabolic acidosis may play a role as well. During prolonged fasting, the metabolic rate decreases to preserve energy, which slows the loss of body mass.
Changes in hormone levels, especially those that regulate glucose like insulin and glucagon, occur after three to four days without food. The body's transition into a state of starvation involves a switch to ketogenic fat metabolism, and when the gluconeogenic response isn't enough, muscle wasting becomes evident. Lastly, the transition through absorptive, postabsorptive, and starvation states underlines the adaptable nature of metabolism during fluctuations in nutrient availability.