remind her that sex burns of more calories than general exercise and its a win win.

Tell her it's been proven that women have poorer spacial awareness than men, so she is unqualified to make such a claim.

There is no way you can answer a question like that without sinking deeper into the rabbit-hole.

"Oh hell, you're not pregnant are you??? Buggerbuggerbuggerbugger..."

I show her photos of western women, to give her a sense of perspective.

"No, of course not, it's just that outfit..."

Buy her some chocolate to soothe her. ;)

Well, duh! Why do you think I got you a gym membership for Valentine's Day?
More cushion for the pushin'?

Maybe:
Get over it or do something about your self-image. You don't hear me complaining about what's larger than normal on me, do you? (my nose)

Or:
Whatever. I think you are sexy and isn't that what matters? I really just want you to feel comfortable about yourself. If that means losing some weight, then I'll love you just as much then.

Well, she has asked that, and my response is always "a little bit... but I prefer it that way, honey."

Surprisingly, she doesn't mind that answer.

There is no right answer - so don't answer her question. Say something like "I think you look awesome."

Very important: After she asks the question DON't look at her, DON'T think. If you say something, say it immediately.
Don't criticize her clothing, so never say "it's just the dress".

Correct, because that just means a shopping trip in which you have to wait while she tries things on for your approval.

There is a reason 95% of all violent crimes are committed at home...

So does everyone just have defective girlfriends, or did I just luck out?