Do American always eat this small

Please don't get me wrong, I am not trying to be insulting, I am just curious, Everytime I watch an America movie, I always see them eating very little food. I used to myself, is that all he or she is going to eat this morning? It's only on few occasions that I saw them eating plenty and it is usually as a family. It's just that.... I am a Nigerian and we are always eating enough. I mean... Something that will hold us for a long time. So, it is quit amusing when I always see them eating very little food and they will be okay for a long time. Is this how it is in real life? Or it is just Hollywood?
PS: Honestly these white dishes ALWAYS look awesome. Da the names are really good to say. I will try them one day. Thanks.