The Science behind a 24-hour fast

Nancy Jaiswal

Jun 21, 2026

​Insulin levels begin

​As food is no longer entering the system, insulin production decreases. Lower insulin levels encourage the body to start accessing stored energy reserves.​

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​Glycogen stores decline

​The liver's glycogen stores provide energy between meals. As fasting continues, these stores gradually become depleted and less available.​

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​Fat burning increases

​With glycogen reserves falling, the body increasingly relies on fat stores. This shift helps provide energy when glucose availability declines.​

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​Hunger signals change

​Many people notice hunger arriving in waves rather than continuously. Hormones involved in appetite regulation contribute to these changing sensations.​

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​Hormonal activity adjusts

​The body makes adjustments to support energy balance during fasting. These hormonal changes help manage fuel use and other functions.​

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Refeeding restarts digestion

​Once the fast ends, the digestive system resumes processing nutrients. The body shifts back toward using incoming food for energy.​

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