Most of my social life revolves around eating. This is something I cannot change due to timing, office arrangements, and the culture I'm surrounded by. I also cannot subtract myself from social situations, lest I become a lone wolf. And not that I'd like to - in general, I appreciate interacting with friends and coworkers. However, everybody around me seems to have a predilection for sugary or greasy stuff. For me, it is hard to refuse the food, but my stomach doesn't quite like it (Disclamer: I am not trying to lose weight, but I think these is the best place to ask about how to create this type of habits.) Long story short: I get diarrhea and cramps. Not every time, but lets say 1 out of 3. The symptoms go away if I suspend those food.

(Someone suggested me to be a "contextual vegan" - approach social situations like I was vegan (I'm not), and that way I'd have an excuse to refuse unhealthy food. But this is not a solution. Vegan doesn't necessarily equal healthy. There is plenty of greasy, sugary, and hyper-processed vegan food. As a matter of fact, there are several vegans in my office, and to not leave them out, all the cakes we eat arealready vegan, which doesn't necessarily translate in less sugar.)

TL;Dr: How can I avoid eating junk food while everybody around me are eating it?