Eleven stages, measured in people, each with its confidence.
What studies measured in healthy adults, not a reading of your own body. During a fast the stage you are in is pinned at the top as Now, with Next and how long until it; the rest is grouped by day, and a tapped row opens with the stage's sentence, how it feels, what to do and its papers. Under the timeline, "Also worth knowing" scrolls sideways: autophagy, hunger, sleep and mood, inflammation, longevity, each an explainer card and never a stage. Stages to 36 hours are free; the two stages past 72 hours are reached only on the supervised plans.
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Free
Your last meal is still being absorbed. Insulin is high and the liver stores glycogen.
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Free
Insulin is back at baseline. The liver releases stored sugar and begins making new glucose from other sources.
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Free
Fat is released from stores in larger amounts. Ketones are usually still near baseline.
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Free
Blood ketones pass 0.5 mmol/L at a mean of 21 hours, SD 3 hours. Timing varies from person to person.
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Free
Most of the liver's stored sugar has been used. The body now makes almost all its glucose fresh.
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Free
Ketones are a major fuel. Blood sugar settles in the low-normal range rather than falling further.
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Pro
Ketones high, noradrenaline about doubled, resting metabolism slightly higher. The last stage of any unsupervised plan: plan your refeed now.
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Supervised · Pro
Ketones spare muscle protein. Reached only on the 96 and 120‑hour plans, which run for people fasting under a clinician, confirmed before every such fast.
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Supervised · Pro
Over 1,000 plasma proteins change only after day 3. The studies run to day 7; the timer stops at 120 hours, and only the supervised plans reach this stage.
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Beyond the 120‑hour ceiling
Studied only under medical supervision with electrolyte monitoring and slow refeeding. No plan in Nesteia reaches it; a running fast ends itself at 120 hours.
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After every plan
Small first meal. Build up over two days after a fast over 48 hours, and over at least three after a supervised fast; electrolytes shift when eating resumes.
FreeAt hour 30: Glycogen largely spent — Most of the liver's stored sugar has been used. The body now makes almost all its glucose fresh.
- Measured in humans · high
- Direct measurement in healthy adults across several studies.
- Measured in humans · moderate
- Fewer or smaller studies, or wider variation between people.
- Animal or indirect evidence · low
- Used only for explainer cards, which is why autophagy is never a stage.
Tap a stage for its note; arrow keys move along the strip. Sources: 22 primary papers and two clinical guidelines, cited as links on each stage and explainer card and listed behind the "Sources · 24 papers" row at the foot of the Stages screen in the app. Reading all eleven stages and the Sources screen earns the Outcrop badge (the Explorer family) on the Strata page.