Small Human Study (12 People): Seven Days of Fasting Change the Body Strongly After About Three Days
A study in humans shows that prolonged fasting triggers major changes throughout the body. Many of the most striking effects appeared only after about three days without food.
1. What the Research Says
The work (Nature Metabolism, 2024) followed about 3,000 blood proteins in 12 healthy volunteers across a seven-day water-only fast. It describes when the effects appear and suggests that treatments could one day mimic them.
2. How It Fits Earlier Research
Earlier work on fasting physiology already describes how the body shifts its metabolism during prolonged fasting and how ketone bodies rise as signalling molecules. The new finding that the most striking changes appear only after several days fits into this picture. Energy metabolism in the liver. (2014) · Ketone bodies: a review of physiology, pathophysiology and application of monitoring to diabetes.1520-7560(199911/12)15:6<412::aid-dmrr72>3.0.co;2-8) (1999) · Ketone bodies as signaling metabolites. (2014)
3. Source
ScienceDaily: Scientists reveal what seven days of fasting does to the human body (2026-10-05)
Full evidence overview: Prolonged fasting
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