For most what you eat matters a lot. A high protein / fat diet gives a huge amount of energy. A high carb diet makes you hungry very fast and then a huge drop in energy. If I eat a small light breakfast of a bagle and cream cheese, or a banana I am more hungry, and have less energy than if I ate nothing at all. When I eat bacon, eggs, sausage, cheese for breakfast. I have a ton of energy all day. Lately, with WFH I have been skipping breakfast, and eating "breakfast" during lunch, but that same food. I have lately been doing a 20 hours daily fast, eating in a 4 hour window, and a 1 day a week fast. And I have so much energy and almost never hungry, and I think keeping low carb is a big part of that.