In 12 healthy volunteers, a seven-day water fast shifted thousands of blood proteins after about day three

What the research found

Study (12 healthy volunteers; water only for seven days). ScienceDaily carried the Queen Mary University of London account on 5 October 2026. The journal paper is older than that news date: Maik Pietzner, Claudia Langenberg, and colleagues, Nature Metabolism (2024; 6(4):764; doi 10.1038/s42255-024-01008-9), with the Norwegian School of Sports Sciences. About 3,000 blood proteins were measured before, during, and after the fast. The body shifted from glucose toward stored fat over the first two or three days. Participants lost an average of 5.7 kilograms from fat and lean tissue. Three days after eating resumed, weight was still down, most of the lost lean mass had returned, and the fat loss remained. About one third of measured proteins changed, with a coordinated shift after about three days that the authors say was not explained by weight loss alone, including proteins tied to support around neurons. The release does not give sex or age. Langenberg said the wider changes were visible only after three days of total calorie restriction, so shorter intermittent fasts are not shown to do the same thing. This is not a plan to stop eating. Educational notes. This is not medical advice.

Evidence level: Human study. A study in people, but an association isn't proof of cause.

Read the original at Queen Mary University of London / Nature Metabolism