Hello Hello Phobia! In the way it is currently implemented if you do not want your character to gain weight, no worries! They have a calorie limit you can see on screen, they will only gain if the amount of calories greatly goes over their maintenance. Even cooler than that the character can lose weight if you start to stuff her with less calories! In other words be mindful of how many calories your Feedee eats otherwise she may get bigger than you'd like.