As their blood sugar levels drop very low they feel hungry, fatigued or jittery. Of course I routinely see folks that have inherited a Mixed or Hunter-gatherer metabolism that consume caffeinated drinks. The difference here is that they usually drink them shortly before, during or shortly after eating. They simply cannot tolerate several cups without food as can their Agriculturist counterparts. Your eating patterns also give an indication of inherited metabolism.
Agriculturists can have a small breakfast and then go without any food until late in the afternoon.
Of course they may have several cups of coffee or other caffeinated drinks to help sustain them along the way. In many cases Agriculturists report feeling better with the less they eat. They might also find themselves in the same situation within 3 hours after lunch and then again just before bedtime. If Hunter-gatherers don t eat breakfast they may find that they can go without food well into the morning hours. If they forgo eating breakfast no insulin is released and blood sugar levels will remain relatively stable.