What realistic weight changes can you expect from a 7-day water fast?
Most healthy adults lose 4–10 lb (1.8–4.5 kg) during a strict 7-day water-only fast, depending on starting weight. Roughly 65–75 % of that drop is water and glycogen, so half or more returns within a week of re-feeding. Pure body-fat loss averages 1–3 lb (0.5–1.4 kg). Muscle mass declines unless resistance exercise or sufficient protein is resumed quickly. Fasting longer than 48 hours carries real risks and should be medically supervised.