I don't know if this will make you feel better, but as a longtime fan of Miss Manners, I never, ever comment on another person's weight for several reasons. First of all, I think it's rude to even suggest that I notice another person's weight. Commenting on a loss means I've been paying attention to their weight (and how will they feel if they gain the weight back?) and other people's bodies are none of my business. Second, people lose weight for all kinds of reasons, including grief and disease. My mother got a lot of compliments after my father's sudden death, and it was disturbing and hurtful to keep getting told how great she looked when her world had fallen apart. You could have lost ten pounds because you found out your husband was cheating on you. You're using the word "colleague" here, so it doesn't seem like you're referring to close friends.
To your point, I don't comment on people's weight, either, unless they are actively talking about it themselves. I know how sensitive a topic it can be for lots of people both thin and heavy. It's just been so much the focus of my last six weeks, that I guess I was wanting SOME kind of validation. According to Dr Lisle...we are wired to want it...in fact, we seek and need it. And to say that we don't, according to what he said in the interview I listened to today, "is pure BS".
I know this is going off topic, but it was a big part of that interview and wildly fascinating. Dr. Lisle spoke extensively about how we get our motivation and esteem--different from self-esteem from the validation we get from others in our lives.
A large measure of a woman's self-esteem comes through her weight. Not because of societal expectation necessarily. His take was really eye-opening. It had to do with getting positive feedback from potential mates. But he made a strong point with this, whether male or female, that we need to pay attention to the inner validating voices...the self-esteem mechanism to strengthen our resolve, especially in the beginning stages.
It was a fascinating talk. The link is somewhere earlier in this thread. Or, it's on you tube...It's Chef AJ interviewing Dr. Doug Lisle.