Throughout the levels are food items (and occasionally presents) that are both helpful and harmful to your character. Simply eat each helpful one (in addition to those found in presents).
Good: Candy Cane, Bowl of Cereal, Bacon & Eggs, Watermelon, Pancakes, Cherry Pie, Fries, Pizza, Fudge Sundae, Hamburger and Fudge Cake.
Presents: Food (Can be good or bad), Rootbeer and Fudge Sundae
It's been confirmed that harmful foods do not count towards this. However whether or not food contained in presents count toward the achievement is still unknown.