One who eats bad food like candy, frozen pizzas, otter pops, pop tarts, and so on and doesn't eat any healthy food. Reflects that of a college diet. The person does not even need to be fat to be a fatty cakes, they can be skinny and eat a whole lot of crappy food.
Also refers to a Donut.
Yo hommie you are such a fricken fatty cakes put down the swedish fish and cheese cake. Fricken Fatty cakes.
That chick is skinny but she is one fatty cakes.
Hey officer how did your fatty cake taste.