How much wieght will i lose on a 20 day fast?

I cannot estimate how much weight you will lose. I can tell you that once you start eating again, the weight will come right back. You would likely achieve better results by eating high protein and exercising.

If you fast food and take vitamins and drink plenty of water or other liquid you will lose about 15 lbs. It's not worth it because of the side effects of a total fast. Believe me I know. I fast for 21 days every year. I do it for religious reasons, but, there are side effects.

If it is done under a doctor's care you will not die. I have been on over a month long fast many years ago when I was 17 years old in an experimental program under a doctor's supervision. I lost a lot of weight, but my hair also started to come out because my scalp shrunk so much. I took several pills and capsules he gave me. I wouldn't do it again, even under a doctor's care because the weight came galloping back right away. It never did anything for my eating habits. I had to learn how to eat right on my own. Slow and steady is the only way.

It wont matter because you'll be dead.

I am doing a 20 day fast and expect to lose about 26 pounds. My last one I did was 11 days and I lost 16 lbs like 2 years ago. I keep losing weight after the fast but I was watching the foods I eat(no bread, rice, pasta, sugar).