How much weight loss can you lose on a water diet?

Unhealthy loss. Fasting is an unhealthy and unsustainable method of weight loss which is not recommended. Any weight that is lost is from water and/or muscle mass loss, and the weight will be gained back as soon as the fast is ended. Moreover fasting can lead to serious complications such as dehydration, kidney failure and other dangerous complications. See your physician to discuss healthy ways to lose weight.