I see myself fasting on a Sunday when I sometimes drive 10 to 15 hours behind the wheel of a taxi even if it only burns 135 calories/hour... I don't think I can stay focused enough if my stomach is crying out for food. ..My brain will automatically send me signals of distress....
it's normal! Living organisms have biological (and cultural) rhythms that constantly inform us. You will certainly have noticed that when you miss a meal at a fixed time, shortly after you are no longer "hungry" or even when you are upset.
It is therefore not a distress signal, but a cultural reflex. But on the other hand, food makes you as addicted as drugs because it lacks the memorized pleasure hormones.
The human being is like an automobile (sector you know well) you cannot repair a vehicle while it is running and half a day may not be enough for a repair. You have to check, control, the various elements that are wrong and find the right repairs and / or changes to make.
"We make science with facts, like making a house with stones: but an accumulation of facts is no more a science than a pile of stones is a house" Henri Poincaré