It's vs Its

It's fucking confusing. Well, not really, but I keep making mistakes anyhow. /r/ simple way to remember which is which.

The cat's food
The dog's food
Its food. <-- WHERE DID THE APOSTROPHE GO???

Its fat <-- The fat belongs to "it"
It's fat <-- It is obese
Sheila is fat <-- Sheila is obese
Sheila's fat <-- The fat belongs to Sheila
FUCKING PARADOX!!!

>>1
Better yet, use charts:

His dog
Her dog
Its dog (notice, no apostrophes on any of these possesive adjectives)

He's a dog
She's a dog
It's a dog (notice, apostrophese in all of these pronoun-verb contractions)