"I think if it's done in the context of shopping with a friend, and that friend asks the question when trying on something, then it's doing her a service to tell the truth.
On the other hand, in some cases, I guess you could consider that the clothing isn't what makes her look fat, it's her excess body fat, so saying "no, of course not" isn't really a lie, but a different interpretation of the question. ;-)"
I agree with everything you've said, Kathryn. If I go shopping with someone, I'm definitely going to say things like "they're both nice, but the blue looks better on you than the green". In fact, when I'm shopping by myself, I'll always give other women unsolicited opinions, and they give them to me as well. I've never had my feelings hurt, and I don't think I've ever hurt anyone's feelings, and yet I think we're all being honest and it's SOOO useful.
If anyone ever asks me "does this make me look fat?", I'll just say "I don't know about that, but that one doesn't look as good on you as the first one you tried on", and mean it.
As you said below, you can be honest, avoid telling lies, and still avoid hurting people at the same time, and unless someone says to me "Do you think I'm as pretty as Rachel Weisz?" (and who would ever say that???) they need not be afraid of my answer.
Nancy