I've had the misfortune of knowing multiple people whom I think of as "food pushers" or "food shovelers." These are folks who want other people to eat more and more and more.
They're not to be confused with people who inadvertently push food once in a while. I think some of those are honestly ignorant about varieties of normal food consumption. Consider a man on a date who's surprised that she "didn't eat very much" when in fact she ate a perfectly normal amount of food for a woman, or someone who offers a huge spread for lunch because her family ate dinner at noon, or a cultural difference where one person feels required to offer as long as the other accepts (while the other feels required to accept whatever the other offers, leading to mutual misery). The common thread is that at least one party truly doesn't know the norms of the other, so that they can differ without either being wrong.
Honest ignorance of others' norms will clear up with time, but some people never seem to get it cleared up. Indeed, some people plainly just don't care. I believe these people have some sort of problem.
They monitor you at dinner gatherings, demanding that you eat double helpings of every dish. When you have finished eating, they bellow repeated offers to hand you more food, any food, as long as you eat more. If you decline a second brownie they will offer it six more times, then ignore all your refusals to hand you the brownie plate with a knowing smile. They may even scoop food directly onto your plate, ignoring the fact that this is a gross violation of personal space. They aren't necessarily prodigious eaters themselves, but they are bound and determined that their target will consume huge quantities of food.
They drive me nuts.
I've long wondered about people who worry about how to explain that they no longer drink or no longer drink heavily. Why do they think that others will even notice? Don't they know how to decline? Why don't they just say that they're fine, thanks, and get on with the business at hand? Don't they know the common convention of saying that they're "fine" or "okay" to indicate that no further offers are needed?
As I've heard more stories from people using the Sinclair Method, I've come to understand that there really are people out there who closely monitor other people's alcohol consumption and press them -- sometimes quite hard -- to overdrink. I don't know if these people are alcohol addicts seeking company or are in the grip of some very strange notions about hosting or are just crazy. Alcohol shoveling makes no more sense to me than does food shoveling, but apparently it exists.
How to handle it? I know of no way to get these people to stop; the best we can do is to just manage the situation without being forced into overconsumption by them. Essentially, this means declining all verbal offers and ignoring forced food/drink completely. If someone offers you a beer twelve times, you decline twelve times. If he then holds a glass of beer out to you, you ignore the proffered glass and speak of something else. If he grabs your water cup, dumps out the water, and fills the cup with beer, you ignore the beer and get yourself a new cup of water.
There is no point in trying to reform these people. If you decline three times and then refuse to decline a fourth because the shoveler is being rude, your silence will be taken as consent and you'll end up with item X. If you give a reason, even an inarguable one like "I'm full," they will find a way to argue. Even if you get completely fed up and dump the unwanted item into the sink while repeating that you don't want it, they'll just hand you another portion along with some absurd reason why you should consume it.
These people are infuriating, but fortunately they're not very common. Most civilized human beings will accept "no, thanks" as answer either upon first hearing or after you've assured them that "I'm fine, thanks." The shovelers are . . . odd.
Even if you're facing a contingent of several of them, so that they seem to normalize each other, remember -- they're the ones with the problem, not you. You're not weird or rude for declining. They're weird and rude for insisting so forcefully.