Often others who need to lose weight feel guilty or threatened when a friend, family member or co-worker decides to lose weight. There is safety in numbers and when one of you makes changes it can be intimidating to those around you.
You and your friend need to stick to your guns and support each other and ignore what the others are saying. It's hard to resist the food pushers but if you have buddy then it is a lot easier.
The way I deal with this kind of thing is with humour, make a joke about whatever is going on and laugh it off, eventually these people will realize they can't get to you and move on.
I used to have co-workers say "Salad again? Is that all you ever eat?" my reply was "Actually I do eat champagne and caviar at home but I thought that was too fancy for the office" and laughed it off, eventually they left me alone to eat in peace
Also if you tell people you have to eat better for health reasons(which is true as you are trying to adopt a healthier lifestyle) or "doctor's orders" they are less inclined to bug you