Regarding the "food pushers" tell them you are watching what you eat. If they insist a second time that you "have more," "try this," etc., tell them to quit sabotaging your efforts.
Said loudly enough, this will also get the attention of others and perhaps silently shame the food pusher to cease their efforts.
Or, just flat out tell the person "I told you no once, I shouldn't have to keep repeating myself. Stop pushing food on me."
It may be difficult to be direct, but people like that do not respond to subtlety or politeness.
It's about setting limits, for yourself and others.
Acceptance on someone else's terms is worse than rejection.