That's just a personal observation, one I learned as a kid and never forgot, though didn't always follow it as an adult. I've found that eating light improves the concentration. The best is when the stomach is empty but there's plenty of necessary energy available in the previous meals being digested in the intestine, i.e. the catabolic state.
Physiologically it makes sense, when in the anabolic state (after a full meal) the body has to concentrate fully on digesting. The liver goes into anabolic mode, the blood goes to the center, etc. The body has to put off repair until the catabolic because the anabolic takes so much energy and focus.
Physiologically it makes sense, when in the anabolic state (after a full meal) the body has to concentrate fully on digesting. The liver goes into anabolic mode, the blood goes to the center, etc. The body has to put off repair until the catabolic because the anabolic takes so much energy and focus.