It is your choice and your body, you do not need to explain anything to anyone. But! Just always say on facebook "hitting the gym," or pictures of healthy food. Sign up for a 10k or sprint triathlon (even if you do not end up doing it) just tell people "Ya I am training for this sporting event and the weight is just falling off!" Just say I am on the KETO diet and only drink green tea. I told my co-workers which is true, that I am having surgery to fix my debilitating acid reflux that was causing my esophagus to develop pre-cancerous cells, and fix a hernia, so I just say everything without saying "gastric bypass," and I just mention that they are taking part of my stomach to help with the reflux.