Question: how much weight will you lose if you only drink water for a day?
Answer: Because a water fast restricts calories, you will lose a lot of weight quickly. In fact, research shows that you may lose up to 2 pounds (0.9 kg) each day of a 24- to 72-hour water fast ( 7 ). Unfortunately, a lot of the weight you lose may come from water, carbs, and even muscle mass.