Seven-Day Fast Triggers Deep Molecular Changes After Day Three

A seven-day water-only fast drives broad molecular shifts that become most evident after about three days, including changes in hundreds of circulating proteins linked to the extracellular matrix and brain support, alongside a switch from glucose to fat and about 5.7 kg of weight loss. Refeeding largely reverses lean-tissue loss while fat loss persists. These findings could inform therapies that mimic fasting’s benefits for metabolism, aging, and neurological health, though prolonged fasting carries risks and should be medically supervised.