I have experienced this. I have a friend who lost a lot of weight in high school (70+ lbs) and had since gained it all back and more. Whenever we go out, she gets a salad, thinking she is being healthy, but clearly oblivious to the fact that Applebees salads have more than 700 calories. Then when she decides to get something unhealthy, she wants to force it on, me too knowing that I am not eating certain things anymore.
She'll say "come on, just eat it". It annoys me. I think people who do this feel badly that they, themselves aren't eating healthy so they want you to join them in their poor eating habits to make them feel better.

Even though I am at a healthy weight, and most of my friends/family know I am trying to shave off just a few more pounds, no one ever pushes food on me. Who knows? Maybe they think I could stand to lose the extra pounds. lol

My mom was a big food pusher, though. Not because she was trying to sabotage, but because she showed love through food. Wish I had recognized it when she was alive... I would have eaten more just for her. She felt rejected when I rejected her food.

But that's a personal ramble, lol. I think, with food pushers, there are all kinds of motivations behind them. Some don't want to see you succeed, because the only way they feel good about their own successes is when they see other people fail. Others are simply being jerks, because they like teasing and taunting. Some may be genuinely worried that you'll become too strict and end up with an ED. Others want to justify that people on a diet are "no fun." And some could simply just be trying to offer you "tasty food" because, well, they like food, too, and can't imagine anyone who doesn't.