Answers are generally never simple. But there are some simple answers. Like the answer to "Do I look Fat?".
The answer : "No" or better "Of course NOT!"
Unless the "asker" is visually challenged, the asker knows the answer is Yes. The asker asks your help, only to float in denial land, and you are not expected to make them crash land to reality, with Your Yes, unless you wanted to be hated, forever.
If you find this tough to accept or understand; well, we don't tell, first kill the chicken, when asked for a chicken recipe, or Boss I want to wring your neck for waiting till evening to give me this job or I want to marry you to be my unpaid maid. Its not about thoughts, its about How You make them Feel. And thats why I am NOT saying "You are a Sick Sadist, who confuses being truthful with being factually correct. Don't you have any mercy within you??"
We are humans! Our best invention is Lying..If you are still uncomfortable with a No and tempted by Yes, Wait, there are other options :
1.The fabric has shrunk? or The tailor has messed it up again? or Salesperson gave you wrong size..or the Labels say XL but the dress looks Medium. (Always blame someone - The Cricket Analyst style)
2. Wear Well Fitted, Vertical Designs with a V neck and smaller prints. And please throw away those high waisted pants with tapering legs. You would look a lot thinner. (Fashionesta style)
3. Hmmm Of course Not! Look in the mirror! (It looks cloudy but it won't rain - Meteorologist style)
4. What matters is not how you Look, but how you Feel! How do you Feel? Surely Great! (TV Guru style)
5. Oh I dropped my lenses again! or Something wrong with my ears..What did you say? (Bollywood Slapstick comedy style)
6. Did you know what Sharukh did...? (Distraction is Best - Breaking News style)
7. Lets discuss it later..(The Judicial style)
8. You look Sexy! (Sex sells colas and cars and cement - The Ad industry style)
9. Lets ask @!$% and %$^% also (Lets appoint a Committee's equivalent in the Political style)
10. Do You think I look Fat? (Let me get even with you for making me feel guilty about lying - Spousal style)
11.You make me feel like a Beauty Pageant Judge! (The Successful Employee style)
12.I asked the same question 3 months back but now I don't ask. You know why? I joined $##@$, ate $#@$^#. And now you can Earn Money, Eat whatever you Want and Never Worry about being Fat..(The "friendly MLMer" style)
13. Why? (Questioning the Obvious, Philosopher style)
14. I was just being sarcastic when I tweeted you look fat. (Shashi Tharoor style)
15. No dear, have a Cookie. (Nobel Committee style)
PS : Please refrain from being Factually Correct. Since Saying "You look Fat" can be hazardous to Your Health..(And if someone murdered you for being "truthful", who would read my blogs?).