Awww...
Your doggie is not that "fat".
In my country, when a child is termed "fat-fat" it is a cute endearment term... eg. my nephews were very cute & chubby as toddlers and their grandma loves feeding them... so they are called "lil' fat-fat".
Nowadays, I call my Roman my "fat-fat" or "Mr. fat-fat" an endearment term because I love feeding him so much (especially hand feeding him)!
"Fat-fat" as foot stool...
Yep, he eats laying down sometimes... lazi dawg!