I get grief all the time, and I can understand why as I'm not big - I'm only 9st 8lb now (erm, 134lb I think?), dress size 12 (think that's American size 8?) but I want to lose a stone to take me back down to 120lb, where I felt happiest and all my clothes are in this size. I'm only 5ft 4in so not tall, and my current body fat% is 27%, which is too high for my frame. But I always get people telling me I don't need to lose anything - tonight at my slimming class a woman who I don't know said to me "Why are YOU on a diet? You're not even fat!" with a real scowl on her face
I think taking control of your body and making a positive change frightens people to death. It makes them think about their own bodies and things they'd like to change and makes them feel inadequate. If you've always been the bigger person, it makes them look good. If you are now becoming slimmer than them, they will then become the bigger person, which probably terrifies them! They also won't like the fact you are getting more attention etc. It's just fear and envy most of the time.
I also find it hilarious that people look at you like you're crazy when you eat "weird" foods when you're eating healthily - even though people don't think twice about shoving processed McDonalds down their necks? It seems to be the norm to eat anything that comes in a packet, but if you eat anything in its natural state you get stared at and comments made, then everyone looks at you and you get really self-conscious...sigh