Seven-day fast alters about 3,000 proteins across the body, study finds

A Nature Metabolism study of 12 healthy volunteers on a seven-day water-only fast found that roughly a third of about 3,000 measured blood proteins changed, affecting all major organs. Participants lost an average of 5.7 kg; three days after resuming eating, fat mass stayed reduced while most lean mass returned. Notable molecular shifts appeared only after about three days without calories.

• 12 volunteers fasted on water for 7 days; ~3,000 blood proteins measured
• Average weight loss was 5.7 kg from both fat and lean mass
• Three days after eating, fat stayed lower and lean mass mostly returned
• About a third of proteins changed, with effects across all organs