I made friends with 3 other mums at baby-yoga and we all went for coffee afterwards. In the queue, I recommended the cakes from this particular coffee shop and they all laughed and said they couldn't eat cake as they were trying to lose baby-weight. One added that she is diabetic. They ordered skinny-lattes/flat whites and I ordered a frescato thing with cream and a slice of chocolate cake, without thinking anything of it. I'm underweight and find it hard to gain any, so I always get cake and high-calorie drinks.
They all watched me eat it and kept making slightly sarcastic comments (eg must be nice to be able to eat cake, that cake looks amazing etc) and I started to feel like I'd commited a faux-pass 
Was I insensitive? Should I have just ordered a drink? Please be honest, as this is likely to be a weekly thing and I don't want to upset anyone.
If you were on a diet, would it upset you if a friend ate cake in front of you?