This podcast provides a detailed overview of metabolism, defining it as the complete set of cellular processes essential for survival, which are categorized into catabolic (energy-producing breakdown) and anabolic (energy-consuming synthesis) pathways. It emphasizes that metabolic regulation is heavily dependent on three main factors: hormone levels (particularly insulin and glucagon from the pancreas), the availability of substrates in the bloodstream, and input from the nervous system. The text further explains the metabolic shifts that occur during the well-fed state, where insulin dominates to promote glucose storage and uptake, versus the fasting state, where glucagon and stress hormones increase glucose production and shift tissues toward utilizing fatty acids and ketone bodies for energy. Specifically, the regulation of blood glucose by these key hormones is highlighted, demonstrating their antagonistic roles in maintaining energy homeostasis.