That alone was probably miraculous or supernatural. Most of us would be dead after40 days without food. The number of days is interesting since 40 was the number of days Noah was in the ark and I think the number pops up in the Bible elsewhere as well.
I believe the Father wanted His Son to learn to rely on the Holy Spirit moment-by-moment, challenge-by-challenge:
Because he himself suffered when he was tempted, he is able to help those who are being tempted. Hebrews 2:18
and
During the days of Jesus’ life on earth, he offered up prayers and petitions with fervent cries and tears to the one who could save him from death, and he was heard because of his reverent submission. Son though he was, he learned obedience from what he suffered.... Hebrews 5:7-8