Question

If we miss our breakfast, we feel tired and exhausted why

Answer 1

The required energy is not provided to the brain and other vital body parts this induces fatigue to the muscular component and failure of not getting the energy for long periods of time might lead to starvation, malnutrition and death. So, to avoid all these incidents one has to gather and live for food, water, nutrients, vitamins, etc. for survival cause and to save the humanity from further irreplaceable damage. This is the prime reason for the state of affairs leading to a dispute for natural resources, we don't get that much resource for the daily living making us resurface everyone we see a food or a breakfast or dinner or lunch in the table. If we by chance skip your or our breakfast you are, unquestionably, gaining weight, slowing down your metabolism, have higher blood pressure than the normal due to stress and high cortisol levels, the hormone tryptophan or the opener to happiness will severely go down making you irritable and anti-social if not having a brunch or a mid-day meal, etc. for your advantage and the benefit in this vast world full of competitions.

Answer 2

i think its becoz we sleep for 8 hours so this creates a huge time gap between our intake of food which makes us hungry due to this we are also advised to eat heavy breakfast.
hope it helps