I was public about it - but not in a telling everyone about it. But, I posted a weight loss blog on FB, so if they are friends on FB, they see the links daily to my blog. I didn't tell anyone else, but after awhile it became quite obvious.
At first I didn't tell anyone (I didn't really see a reason to)...but uh...48 pounds in it's kind of hard to hide it anymore. I've pretty much had to start being public about it and I don't really mind answering questions if people have them. However, at the same time I don't really think I should have to answer any questions if I dont' want to.
My experience was similar to sontaikle. I didn't go out of my way to talk about it when I started, but after a while people started noticing and I would tell them that yes, I was working at losing weight. But I still don't go into much detail unless they specifically ask. Interestingly, the person at work who asked the most questions is very thin and fit and is extremely careful with what she eats to stay that way. The second most questions came from someone who has been working at losing weight but who will freely admit she has not been as diligent at it, although she was not nearly as big to start with so even at 50 lbs gone, I still have a bit more to lose than she does.
I didn't tell people just because I didn't want the "food police" around. I got so tired of people giving unsolicited advice (like just run after every meal). Besides, I like surprising people!
I tell the people for whom it's relevant - people I eat with. That includes my family, a couple best friends, my boyfriend, and his family. Also the guy at Starbucks, because he asked why I wanted a tall skinny. Answer: because I want to BE a tall skinny! ^.^