Phase · Ketosis
Ketosis, explained.
Hours sixteen to twenty-four. The liver makes β-hydroxybutyrate; ketones cross the blood-brain barrier and the brain begins burning them alongside glucose.
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How the body enters ketosis
A walk through the switch from glucose to ketones — what happens in the mitochondria, why the brain adapts so readily, and the signs you've arrived.
Mechanism · 7 min
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20 hour fast stages (20:4): what happens hour by hour
What typically happens during a 20-hour fast, hour by hour: how ketosis deepens between hours 16 and 20, how it differs from a 16-hour fast, and who should take care.
Timeline · 6 min
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24 hour fast stages: what happens hour by hour
What typically happens during a 24-hour fast, hour by hour: from lipolysis into ketosis and the start of the autophagy window, and who should take care.
Timeline · 6 min