Fasting's popularity has surged, but a new study from Queen Mary University of London reveals exactly what happens to the body during a seven-day water fast. Researchers tracked around 3,000 circulating proteins in 12 healthy volunteers before, during, and after the fast.
Day 1: The body quickly shifts from burning glucose to utilizing fat stores.
Day 3: Major molecular changes begin. ECM proteins-which support connective tissue, skin, cartilage, and neural tissues-become enriched, suggesting prolonged fasting triggers tissue remodeling and repair, not just fat loss.
Day 7: Brain-related proteins change substantially, including Tenascin-R, which supports neural plasticity and brain remodeling. Inflammation and immune signaling shift, offering potential benefits for rheumatoid arthritis, cardiovascular disease, and cellular stress.
Subjects lost an average of 12.5 pounds. When eating resumed, fat loss was largely preserved; initial weight regain came from glycogen restoration and water retention.
Claudia Langenberg, director of the Precision Healthcare University Research Institute, said: “For the first time, we’re able to see what’s happening on a molecular level across the body when we fast. Popular diets that incorporate fasting claim health benefits beyond weight loss. Our results provide evidence for those benefits, but they were only visible after three days of total caloric restriction-later than we previously thought.”
Researchers caution that prolonged fasting is not suitable for everyone and advise consulting a medical professional before attempting it.