only one person in the Bible was said to do a 40 day fast and that was God in the flesh, Jesus Christ.
Beware the serpent was subtil and took away from the word of God and added to the word of God when he deceived Eve.
I hope your fast goes well for your physical needs. I do know that fast can help physical ailments and cleans toxins.
I would encourage you to read the post below "Biblical Fasts" it will give you a better idea of what fasts were for and why persons of the Bible fasted.
In the study a majority of the peoples fasts were one day, then fewer went for three days, one man did a seven day fast, Paul and some sailors went 14 days fasting, but only Jesus did a 40 day fast
Bible fasts are not the same as the fasts of the world or other religions.