Daniel 1:11-15

But Daniel said to the overseer whom the commander of the officials had appointed over Daniel, Hananiah, Mishael and Azariah, “Please test your servants for ten days, and let us be given some vegetables to eat and water to drink. Then let our appearance be observed in your presence and the appearance of the youths who are eating the king’s choice food; and deal with your servants according to what you see.” So he listened to them in this matter and tested them for ten days. At the end of ten days their appearance seemed better and they were fatter than all the youths who had been eating the king’s choice food.