During a 24-36 hour fast, growth hormone rises, adrenaline (norepinephrine) elevates, and metabolic rate does not fall — the opposite of what most people expect. One study of eleven lean subjects measured resting expenditure rising up to ~14%; a larger trial found about half that at 36 hours and no significant change in men, so treat the rise as real but uneven and the no-slowdown as the solid part.
This companion explores the growth hormone surge and what it does and does not settle about muscle, the norepinephrine increase and why the metabolic rise cannot be pinned on it, what happens to metabolic rate, how fasting differs from restriction, and what you experience during the hours of a fast. (5 min read)
Written by AI, directed and approved by me. How this is made →