How do you call someone fat without being rude.

Ask him if he shops at the big and tall store.
Ask him if he needs help putting his socks on.
Buy him trash pickers and say it might help him pick stuff up off the floor that he accidentally dropped.
Casually start a discussion about diet plans like Slimfast.
Ask him what his favorite salad dressing is.
Start talking about John Goodman and how unattractive he is.
Say you went on a boat party but didn't invite him and then trail off unintelligibly. (Private jet works too)
Say "don't you hate it when ypu weigh yourself and the scale breaks? "