When Is Water Fasting Needed? Learn to what are the symptoms that show that a water fast is needed. Symptoms can be divided into acute and chronic symptoms. Acute symptoms are a sign that a short water fast is needed. Chronic symptoms show that a long water fast in needed. By the term 'water fasting' we are talking about therapy that lasts about 3 weeks + about 1 week of introducing food and physical activity. During this therapy, clients take in only and exclusively water, while they rest completely in ideal conditions for rest. Throughout the therapy, clients are supervised to keep them safe. Read this blog post now to learn what are the symptoms that show that a water fast is needed.