US restaurant portions are
huge. If you eat like that every day, it will kill you. I think one reason is that the ingredients are cheap relative to other costs including labor. It used to be rationalized by saying that a restaurant meal was supposed to be a rare indulgence, but I don't think that's true any more for a large swath of the population.
Anecdote: I had two long meetings at work last week, that crossed over the lunch hour, so they brought in lunch. Each was from a "fast casual" or "fast food" sandwich shop. There was like 1/2 inch slab of processed meat on each sandwich. I would typically put one thin slice of the same meat on a sandwich that I make for the lunch that I bring to work. I discreetly removed most of the meat and threw it away. I know some people who will take a delivered meal like that, cut it in half, and save the second half for the next day.
Another anecdote: There was an article about a town in Texas that was losing its last restaurant, and the author wondered how people would eat.
Of course to maintain a higher body weight, you need to eat more.