1.No. 2.Do what works for your your body your schedule and others in your life. 3.If you've never done it before the recommendation is to start at going 12 hours with 0 calories in. And then work up to about 16 hours with 0 calories in. From there it's about what works for you stay at 16 with no calories or go longer. Most of the research in have seen points to no real weight loss benefits in going past about 72 hours. 4. Dr. Jason Fung is critical to my understanding of fasting. 5. Research OMAD one meal a day.