What is the Origin of Fasting Metabolic Response?

This response is fundamental to survival physiology, rooted in the necessity to manage energy deficits across evolutionary history. The term focuses on the endocrine signaling cascade initiated when nutrient sensors detect depletion. It is a core concept in understanding metabolic adaptation.

What is the Mechanism of Fasting Metabolic Response?

Upon fasting initiation, insulin secretion falls, and counter-regulatory hormones, notably glucagon and cortisol, rise to stimulate hepatic gluconeogenesis and glycogenolysis. Furthermore, lipolysis increases to provide fatty acids as an alternative fuel source for peripheral tissues, sparing glucose for obligate users like the brain. This shift optimizes substrate utilization based on resource availability.

Fasting Metabolic Response ∞ Area

Fasting Metabolic Response

Meaning

The Fasting Metabolic Response encompasses the coordinated physiological shifts that occur when exogenous nutrient intake ceases, compelling the body to utilize endogenous energy stores. This involves predictable alterations in circulating insulin, glucagon, and growth hormone levels to maintain glucose homeostasis and promote substrate switching. Clinically, this response reveals underlying metabolic flexibility.