How do you dodge an unwanted compliment?

I'm sure that some of you have the same problem I ran into last Friday. I was wearing the outfit above, and we had our work "Holiday Party" which is 1.5 hours at the end of the day with some snacky time foods. In line a coworker told me I looked "so nice" and just as I started to smile and say thank you, she followed it up with "I can tell you've been doing something that works." I know this woman meant to be complimentary, that there wasn't any bit of a passive aggressive dig in there, but still, I had to bite my tongue to rip her a new one for assuming that I wanted a compliment like that. A) I'm not, in fact doing anything to lose weight and I'm not losing weight. B) I find it rude to assume that people are trying to lose weight, because it implies that there is something wrong with their current body.

Weight is such a troubling issue for so many women (men, too) that even compliments can backfire on sensitive people. You might say to someone "You look so great having lost that weight" and they hear 'With that weight you looked hideous'. During the holidays, we'll all run into people we haven't seen in awhile. Instead of talking about someone's weight, why don't you just tell someone they look beautiful if that's what you mean? No qualifiers, no 'you look so beautiful today/in that dress/now that you're skinnier', just tell them they look beautiful. Because when you qualify someone's beauty, you're saying there are times that they don't look beautiful, and I know that you don't want to say that.

Fun 70's effect.

So how would I have dodged that compliment if I had time and I saw that woman for more than a second in a line? I would have said "Thanks, but I'm not losing weight. This sweater is just so pretty, isn't it!" (Which is true, and because of the way it hangs, it does give me a different shape than some of my clothes.) Because she meant well, and I didn't need to go into all of this with a passing business acquaintance. Several of the women in my department are dieting, and they might have liked that compliment. 

How do you address compliments that make you uncomfortable?