When humans developed sophisticated agriculture-which allowed cities and empires-they became shorter-smaller-less healthy.
I Notice-you said despite having a belly stuffed with grain "I'll be about to pass out-my stomach can't keep up with energy expenditure"-
Some folks might take that as a hint that there diet wasn't quite "right"
In respect to our friends on the far side of the Pacific-
You have noticed- Vietnamese immigrants-their kids here in the USA- much much taller bigger than their grandparents-wonder why?? Animal protein and fat(and vitamins minerals that come with it)-less grain-
Same story in Japan-current young adults are GIANTS next to their grandparents-Animal protein-fat-less rice.
Our Pacific Friends-perfect example-thanks!