If your diet is sufficiently arranged to contain as little carbs as possible, this disappears. I went from a heavy lunch person to forgetting to have lunch.

Does the amount of carbohydrates intake impact focus/concentration?

Carbs give you a sugar rush and then everything in the body goes into processing them, slowing everything else down.

You can easily test it, eat something like a subway sandwich. Record how you feel. Now take the exact same sub, but as a salad (no bun). You'll feel markedly different.

This all, of course, depends on a ton of individual factors like insulin resistance etc.

Your example seems to be about refined and simple carbs. Those do spike blood sugar. But a better diet would include more of complex carbs where the blood sugar doesn’t spike as badly as with a diet on processed and refined (fiber-less or low fiber) foods.

For me it noticeably did. Less carbs => better focus. Of course, anecdata, YMMV etc.

For me it required both dietary and psychological techniques to deal with feelings of hunger.

- During my morning fast if I'm hungry I'll mix two tablespoons of psyllium husk with water and drink it. Fiber helps you feel full and in this form doesn't break the fast https://www.ifbuddy.com/nutrition/does-fiber-break-a-fast/

- Psychologically I remind myself it's OK to feel hungry. I reframed feelings of hunger from a signal that I forgot to eat to a signal that in a few hours I'll need to eat, as if hunting and gathering will take a few hours so my body is telling me to start now :-)

Before anything else, one of the factors to consider is adequate hydration. Sometimes people confuse thirst as a signal of hunger for food, and then start snacking or binge eating.

Another big component of hydration is electrolytes, especially sodium. Particularly if you're eating lower carb, drinking coffee, doing some sort of fasting, and/or exercising. If you're doing any of those things, the RDA of sodium is likely nowhere near enough for you.