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Fast 16 hours, eat within an 8-hour window. Most popular protocol.
Scientific metabolic milestones during your fast
Blood glucose peaks, insulin elevated. Body is in full anabolic/storage mode.
Insulin: HIGH · Glucose: 90–140 mg/dL
Glucose absorbed. Liver begins releasing glycogen to maintain blood sugar.
Insulin: FALLING · Glycogen: depleting
Insulin drops low. Adipose tissue releases fatty acids into circulation.
Lipolysis: ACTIVE · Ketones: trace
Liver converts fatty acids to ketones. Brain begins using ketones as fuel.
Ketones: 0.1–0.5 mmol/L · GH: rising
Ketones fuel the brain efficiently. Many report sharp focus and calm energy.
Ketones: 0.5–1.0 mmol/L · Norepinephrine: ↑
Body is predominantly running on fat. Fat loss rate at maximum for daily IF.
Ketones: 0.5–2.0 mmol/L · Insulin: lowest
Cells begin recycling damaged proteins and organelles. Cellular cleanup mode.
mTOR: inhibited · AMPK: activated
Beta-hydroxybutyrate suppresses NLRP3 inflammasome. Systemic inflammation ↓.
BHB: 1–3 mmol/L · CRP: falling
HGH levels rise 5x baseline. Protects muscle mass and mobilises fat stores.
HGH: 5× baseline · Glucagon: HIGH
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Read our science-backed guides: hour-by-hour body changes, 16:8 beginner guide, and evidence-based benefits.
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