God dammit anon. Don't listen to any of these crazy fucks
1) Do NOT go to a fast food restaurant you depraved monster. Go to a bar and flirt with bigger girls or find one on the internet like a normal person.
2) Make it clear you find them attractive but aren't interested in long term stuff, just hooking up. Treat them as people, NOT as fetish objects.
2) IF by some miracle you actually manage to get in bed with a fat girl despite your abhorrent inability to interact with other human beings in a polite and normal manner, don't ask to fuck her back rolls the first time. Regular fuck her like a normal person, make her climax unless you're a scrub who can't make women orgasm in which case give up and go to /r9k/
4) After multiple pleasant fuckings, small talk and hookups (if you ever get this far I would be astonished, it takes lots of patience and a decision not to drop the spaghetti you seem to be filled with) THEN drop the question of "I have some weirder stuff I like, would you mind if we tried some of it? I warn you, it's pretty damn weird." Make sure she knows it's okay to say no and that you're not someone who sees her as (again) an object and offer to do something she finds kinky in return if necessary.
If all these conditions have been successfully fulfilled, lube up her back a lot and then go to town. Preferably make sure you're doing something for HER during this process because goddamn, I can't imagine anything more depressingly horrifying than just sitting there in silence while some pervy dude you just barely met fucks the fat rolls on your back you've been ashamed of your entire life.T. nonfat femanon