Food inside of Pegaxy is a single use item that is used for the same reason as gear - to assist with temporary changes in the Pega's attributes. The same formula stands for food as it does for Gear, see a simplified formula here: Speed <-> Strength <-> Fire <-> Water <-> Wind <-> Light <-> Speed.
This means with every attribute gain comes an attribute loss. The effects of a food last 7 days and can not be removed until the 7 days are up.