Well, you're going to have trouble finding any item that makes you look 'fat' when you're that slender.
Does white make objects look bigger? Yes. It's an optical illusion. For example, I've noticed that dark top + white pants balances out my proportions better -- it makes my bottom half look slightly larger, which for me is good (I have slender hips and a fairly full bust -- my hip and bust measurements are the same, and in a 'perfect' hourglass figure, the hips are two inches bigger than the bust).
But it's a subtle effect, and there are many fab white garments and outfits. I wouldn't let the idea that it makes you appear fractionally larger prevent you from wearing it.
Do skintight or clingy garments make a person look bigger? If the person is very thin, no. If they are anything else, yes.
That's my observation, anyway.
