Fasting?

Hello! My dad said he did this ultimate fasting diet, for 6 days, and only drank this maple syrup/kian pepper/lemonade drink the whole time. He also said you can do it for like 40 days. Is that true?

I know it’s good the cleanse your body and stuff by fasting, and it’s good to fast, it’s just that when your done fasting you eat twice as much for like a week and gain it all back, lol.

I want to start fasting, but I don’t know how to do it PROPERLY, with exercising and stuff. Can anyone tell/help me start it and tell me what to do, to do it properly? Like fast for… 10 days? And exercise for like 30 mins each day or whatever. I’m trying to lose around 40 pounds =O. And diet’s don’t work with me, or at lease I wont make it work, very complicated, lolz.

Please help! Thankies~!