Since the "born again" person remains physically the same, we can say with certainty that the transformation was a spiritual rebirth, rather than a physical one, to quell any suspicion that Jesus was telling adult men and women to return into their mothers' wombs to be born again!
In John 3:5, Jesus explained how the rebirth was to take place. "I tell you the truth, no one can enter the kingdom of God unless he is born of water and of the Spirit. Flesh gives birth to flesh, but spirit gives birth to spirit."
Hence, to be born again requires that we be baptized by water as repentance for our past sins (Arts 19:4), and be baptized by the Holy Spirit to empower us to resist the temptations that lead to sins.
After his spiritual rebirth, the words and action of the physical person would change. His mind would be informed by the wisdom of God, and his actions informed by God's power toward righteousness.
His family members and friends would notice the change in the attitude of his mind, and in the works of his hands. He would have no room in his conscious mind to hold negative thoughts about others. The old person he was before has been supplanted by the new person he has become to complete his spiritual rebirth.
Consequently, his mind would be permeated with the love of God, bringing him joy when he is doing God's will. When this happens, he can then truly say he loves God with all his mind, and be approved by the Holy Spirit as a child of God