I don't tell people I'm not close to (i.e. coworkers who aren't also personal friends) because it's really none of their business and I've gotten enough judgment from other people about my weight and eating-- I'm not interested in more. Now that I'm a year and 4 months out, I feel like it's too late even if I wanted to tell-- some people might feel "betrayed" even if they legitimately have no right to feel that way. I don't really regret being cautious, but I do feel like I'm in a corner where it would cause problems now for me to "come out" to acquaintances who have been very complimentary about my losses. I suppose if someone came right out and asked I would definitely tell the truth, but so far that hasn't happened.
People who haven't struggled with true obesity (and even some who have) are still very ignorant about what it takes to successfully lose and KEEP OFF excess weight. The research is very clear that dieting in the traditional way does not create long-term weight loss, and in fact, stimulates long-term weight gain, but "common sense" says it's so easy to lose weight- just don't eat as much and exercise! I think it is going to be a difficult thing to change opinions about bariatric surgery, but it will happen someday. In the meantime, you have to do what is right for you. This is YOUR LIFE.