When Nebuchadnezzar was the king of ancient Babylon, his policy was to take a few promising young men from each of the kingdom's he captured to groom them to serve in his court. Daniel and his three friends were inducted into this program. While they were being trained and educated, they were assigned food and drink from the King's table. But these young boys purposed in their hearts not to defile their bodies with food and drink that God didn't approve of.
There caretaker was concerned that he'd get in trouble if the boys' health deteriorated. So they asked him to conduct a test: let them eat and drink their simple food for ten days and compare them them with the others. At the end of the trial, they were found to be fairer and fatter then those who ate the kings rich fare. By the end of their training it was obvious to the king that "in all matters of wisdom and understanding," Daniel and his companions were "ten times better then all the magicians and astrologers that were in his realm."