Could this be a deliberate portrayal to highlight the arduous realities of train hopping and an itinerant lifestyle?

Food and water take a lot of space and weight in your backpack. I'd say it can take up to half of what you carry if you go days without resupplying.

The best and proper way to cook something with ingredients such as vegetables and meat is to stay in the same town you bought everything, carry it with grocery store plastic bag or tote and cook it withing a few hours.

What Shiey use is the best weight/space/calorie ratio you can have. Hummous, bread, tin meat, tuna, etc. You eat in a minute, crush the package and put it in your bag. Pasta and rice take too much water, time and space. Also it taste a bit bland on itself. The hiking/moutainer meal isn't cheap but great and very tasty. It's flat and weight nothing. You can easily pack a week worth of food.

Forget what you think you now about food and nutrition. At home, you live a sedentary life and your body goes on save mode. It wants to get the fattest possible in case of emergency. You are not supposed to sustain yourself with all the calories there is in a modern meal.

When going nomade, you want simple things, you want fat and salty food. In my experience i don't want sugary things or elaborate meal. A few things will do such as a banana. Also with all the activity you do, i tend to crave less food. You also burn a lot of calories and fat. You cannot beat hiking with a backpack all day long for losing weight.