When Garfield eats a lot of fruits and junk food he will gain calories. When you reach a certain limit you will be able to break the weighing scale, earning a free point of lasagna to spend however you want.
Don’t forget to activate the Fiesta as soon as it is available! It is important to do it as soon as possible because once you have obtained the required calories you will not collect more of them by eating until you activate the Fiesta reward.
Junk food items are the best ones to fill the Fiesta bar quickly.