I am in the same private little boat. I have only told my husband and my twin- even then I had to make it clear it was not negotiable, I was sharing the information for support and because it would be too much not to tell with this dynamic. I have no intention of offering the information to anyone else, though I don't know yet what I would say if asked. Time will tell.
For me, there is some shame in not being able to lose weight, but more than that I don't want to have to explain myself to people at my age. I had a trial run a while back while I was just "thinking" about it. At that time I spoke freely about it and sure enough - everyone becomes a dietitian and health guru. I had people telling me they will get me in shape. I was athletic when I was younger and have had my weight gain for almost 10 years (around 8-10 pounds a year) and most people just tell me I just have to do what I was doing before. It's just too much to explain to them how the weight gain happened. I lost a son, and then a couple years after my mom and sister to cancer, and during this time I lost control of exercise and weight management. Theres more to the story usually, and I really just want to move on with my life and avoid the lengthy retelling to everyone as I explain my personal health decision.
So for now, I will tell them the TRUTH... I have lost weight by drastically cutting my calories. Maybe after the fact, I will say something, but for now - TMI.