What fasting stage am I in?

When did you last eat?

Your last meal ended

Enter when your last meal ended to see the stage your body may be in.

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The eight stages

Fasting Tracker marks eight stages that your body may move through as a fast goes on. These hours are typical averages, not a schedule: your last meal, how active you are and your metabolism all change the timing, and the later stages, such as autophagy, haven't been timed in people ^1,2.

1. 0 hBlood Sugar RisingYour body is digesting your last meal and using that energy. Insulin is elevated.
2. 4 hBlood Sugar FallingBlood sugar settles back to normal and insulin starts to drop.
3. 12 hFuel SwitchYour liver's glycogen is getting low, so your body starts turning to fat for fuel.
4. 16 hFat BurningYour body starts burning stored fat for energy. Stay hydrated!
5. 24 hKetosisFat is now your main fuel, and your liver turns more of it into ketones.
6. 36 hAutophagyCells may start clearing out old components, a natural recycling process.
7. 48 hDeep RenewalGrowth hormone levels may rise, helping to preserve muscle.
8. 72 hImmune ResetExtended fasting territory. Only continue with medical guidance.

Why the timing varies

The metabolic switch from sugar to fat typically happens somewhere between 12 and 36 hours after your last meal: earlier if you're active, later if your liver started the fast full of glycogen ¹. A brisk walk and a lighter, lower-carbohydrate last meal bring it forward.

Sources

1. Anton SD, Moehl K, Donahoo WT, et al. Flipping the Metabolic Switch: Understanding and Applying the Health Benefits of Fasting. Obesity (Silver Spring). 2018;26(2):254-268. doi.org/10.1002/oby.22065
2. Jamshed H, Beyl RA, Della Manna DL, et al. Early Time-Restricted Feeding Improves 24-Hour Glucose Levels and Affects Markers of the Circadian Clock, Aging, and Autophagy in Humans. Nutrients. 2019;11(6):1234. doi.org/10.3390/nu11061234