I definitely think **gravitycrash and troublmaker **have a lock on the best way to avoid the whole “Does my butt look big” scenario. Compliments for free will make a woman not need to ask for validation. Another way to get validation without the implied threat of injury is asking “Does this outfit flatter me?” Much less of a death trap, because the answer could be “Yes, hon, but I think this shirt/sweater/pants would be even more flattering.” No one thinks they’re called fat. Of course, a properly trained drama queen will be able to go on and on about how none of her clothes work for her anymore. 
In the future, “dumb” yourself down and answer in simple “yes-no” terms. Go with the answers you know she’s reaching for. No sense digging yourself into solo-sleeping nights. Peace.
trublmakr, I think I love you.
RFBluesValentine—How you doin’?
From the right person, the truth doesn’t hurt. My husband and I are not each other’s physical ideals, and we’ve been clear on that from day one. He’s too lanky, I’m too curvy (ahem “fat”). Yet there’s something about him that attracts me, even though he isn’t my usual cup o’ tea. And vice-versa. But in those weak moments when I’m feeling insecure isn’t the time to practice utter honesty. The time for that is when we’re both feeling OK and strong.
When he says, “Hon, those pants do a weird bulgy thing in back,” he makes it the pants’ fault, not mine. But the trick is to say it, blame it on the pants, and do so before she asks. The fact that both he and I know that the bulgy thing is because of my copius bulging buttocks is irrelevant. He’s not critiquing me, he’s critiquing the pants.
Once she asks: Lie. Like a rug. Or, if you feel you must, blame it on the clothing, not her ass. Once she’s asked, though, this is a tricky manoeuver. You must immediately follow it up with a compliment, preferably two:
“Do these pants make my ass look big?”
“Huh. Let me see. Yeah, a little. Weird. Must have been bad cutting, 'cause I love me that ass! No one should be able to make that ass look wrong!”
checks chest for breasts Yup got those.
checks crotch area for definite lack of penis and evidence of vagina Yep.
Right, so I’m a girl. Why on earth do some women play these mindgames? Personally, if I’m asking you how I look in something, I want an honest answer. Yes, or no. Especially if what I’m wearing doesn’t look good! Tell me!
Am I the only woman who thinks like this?
Apparently. Well, you and a few others in this thread. I need to find me a nice down-to-Earth woman like yourself.
So…ahem, how YOU doin’?
There was a penis-size thread a while back in the Pit I think. (I don’t have time to go look for it right now.) Basically, what was said there was that no guy wants to hear that “yes, it’s small, but I *love *small dicks.” This is the same thing. Now guys aren’t usually going to ask a girl if she thinks his penis is too small (although one guy I was with did want affirmation that he wasn’t too small - he wasn’t, but he was insecure). But women do regularly ask the equivalent type of question and the answer - as was discussed in the penis thread - should ALWAYS be non-negative.
“Do I look fat?” The answer is NOT “Yes, but I like fat girls.” See above. The answer is “You look perfect to me” or “I love your figure.” You haven’t lied, but you haven’t insulted her either. I also like the “The pants/skirt/dress isn’t really complimentary to you… you have a wonderful figure and this other dress shows it off so much better” answer that other people have mentioned.
Most of the women I know would respond, “You didn’t answer my question.”
That’s when you distract her by buying her something shiny or sparkly. 
When I ask el hubbo if the pants I’m thinking of wearing to work are too tight, I expect an honest answer. I get one, too.
[aside]
There’s a Twix (I think) commerical with a woman asking her boyfriend/husband if the pants she’s wearing makes her ass look big. Her ass is SO frickin’ big. I think her butt is computer generated or they used a camera-angle trick of some sort because the rest of her body looks somewhat normal. My husband says, no, that’s really her ass.
Has anyone seen that commercial? I haven’t seen it in a couple of months, so it’s a little dated.
[/aside]
I agree with this. If you don’t want the answer, don’t ask!
No, Angua, dear friend, you are not the only woman who thinks like that. Himself has saved me from going out in a blouse that made my side area (bra lines and fat rolls) look like a pack of sausages. Bless him.
So, how YOU doin?
I always have trouble with the “does this make my butt look big” question. If I find a woman to have a shapely behind, I like clothes that make her rear look big. Accentuating the features I like is a good thing, in my eyes. If I answer that question by saying garment x looks utterly hot on her (whoever she might be), she almost always will press the issue and insist on knowing if it makes her butt look big. Well, yes. Yes it does. And I likes it.
I’ll confirm that. Physically, she was different then the women I normally find myself physically attracted to. Not ugly, not a body shape that I would otherwise find unattractive, but different. However, I pursued a relationship because we connected well intellectually, we shared a common mindset, and our brains seemed wired similarly. Yes, there was mutual attraction. Unfortunately, for me the physical attraction wasn’t as strong as I had hoped. However, I thought I’d give it some time, to see if the “chemistry” would kick in from my end. I really wanted it to.
Many of my female friends, and many people on the SDMB, have said that in pursuing a relationship, one should look beyond a person’s outer shell; and apply the “it’s what’s inside that counts” cliche to a prospective significant other. Well, I tried that, and I got burnt.
WhyNot phrased it well when she wrote:
AllGlittery said:
She pulled the “Do you think I hot?” question a couple of weeks into the budding relationship. I didn’t hold back on sincere, unsolicited complements. Still, I’m trying to overcome my “nice guy-dom,” and not smother a woman with complements that are more for my benefit than hers. I’ve been told that when a man offers too many complements, it makes him look needy and insincere. Based on personal experience, that’s true.
Dating. Another doper 
In the interest of full disclosure: I’m a woman. Now that that’s out of the way…
See, your phrasing is different; you ask how your butt looks in those pants - the man (or woman) of whom the question is being asked has all the adjectives in the world from which to choose. The question is not loaded; you really do seem to want an honest answer.
When a woman asks, “Do these pants make my ass look fat?”, she’s directing the person being asked as to how to answer the question. As zyada said before, “fat” is generally a negative adjective, therefore the “correct” answer is “no!”. There’s no question being asked, only a directive being given - “Pay me a compliment”.
As for why some women do this: It seems to me that they ask loaded questions due to their own insecurity, pure & simple. Tell me I’m pretty/hot/sexy/etc. As for why they’re insecure… Pick a reason, any reason.
Damn. And I just noticed that you’re on the other side of the pond from me. Oh well… 
Hey, it could be worse – I could be living a couple of hundred miles from you and dating.
The real moral of the story here is never accompany women going shopping.