Disclaimer: I do not claim to speak for the people of Iran, because: a) I am not Iranian, and I don't know them all. I am speaking from snippets of my own experience, much like the blind men and the elephant. So, here's one snippet.
The Concept of Taarof - There is no word that corresponds to this in English, so a translation might be: the belief of a host that a guest is just being polite and really wants every piece of food in your house, and therefore one must browbeat him until he eats enough to make him sick, and the effort of the guest to avoid being trouble and eat as little as possible, whether or not he is hungry. Well, actually I think taarof means more of the latter - the guest's trying to avoid taking it, but the two play sort of a symbiotic ritual together. This can also apply to other situations where someone is trying to be helpful to another and the other person is trying to avoid being helped, but it reaches its apex in the realm of social eating.
When you visit an Iranian family, they will immediately begin preparing tea and dessert plates of seasonal fruit to serve you, and may also serve regional sweets and nut/seed mixtures. You will politely accept the plates and then proceed to ignore them. They will urge you to eat, and you will take a few grapes to appease them, but it doesn't. They will pare a pear and offer it to you, and you can't really let it go to waste now once it's cut, can you? And then, you really must try these peaches....they are very good.....and then I made this special cake today just for you....
There are certain people who are very good on the host end and others that are very good at avoiding the eating part. For example, there may be a khaleh-jan (means "dear maternal aunt") who makes sure that you have eaten at least one of each kind of fruit in the house and each pastry, and if you don't want tea, she will make sure that someone brings you a sharbat (an -ade, made with fruit syrup and water, or with pureed fruit such as melons), and even though you have something in your mouth every second you are in her house, she is sure you are far too thin, and must have more, and take some home in case you get hungry in the 15 minute car ride home. And then she has to give all the young people some money, and even if you're 55, you're still young in her eyes.
The ones on the guest side that are successful in avoiding eating just seem to have that force of will to politely take a bite and then offer things to others and strongly decline things for themselves. Or they are quick at filling their plate so no one can put something else in it. For example, if they are eating a meal at someone's house, then they eat all the yogurt in the small bowl by their plate, and as soon as they finish the plate with their main meal, they put the bowl on top of it, and make sure chicken bones fill any other available area of the plate and bowl. Otherwise the host will be sure to put another huge kafgir (large flat serving "spoon") full of rice on the plate, because the guest obviously is wasting away and needs more.
An Iranian who arrives in the US and is not aware that Americans do not know how to taarof, may come away hungry the first few times they visit an American family, because the American will offer food, the Iranian will politely decline, the American will say, "Are you sure?", the Iranian will say they do not want any, and then that will be the end of it, to the great astonishment of the Iranian, who will not know what to do if they are not harrassed into eating.
What happens if you eat everything thats offered to you? will you never be invited again? i need to check this point, but so far im super looking forward to my first invite to an Iranian house.