The human body left alone in original East African savannah sorta worked, hunters and gatherers don't suffer from metabolic disease much. (Though obviously they still succumb to injuries, infections and random disease such as appendicitis.)
The human body left alone in a modern supermarket world is way off its original evolutionary envelope. I am a descendant of 300 generations of agricultural people and I still struggle with processing of milk. Most of our commercially sold foods aren't 300, but 1-2 generations old. We just cannot be adapted to that.
> human body left alone in original East African savannah sorta worked, hunters and gatherers don't suffer from metabolic disease
One, we don't know that. But two, it's fair to assume they didn't because their constraint was starvation.
Look, metabolic disease makes sense from a preservation angle. It's a safe assumption, in the wild, that one will not suddenly come across permanent sources of excess calories. So if one assumes starvation is the enemy, and the body finds itself amidst excess calories, it must assume this is a finite resource to be competed for. Herego, stuff your face. Build fat cells. And under no circumstance shoud you give up a fat cell. No, reduce voluntary motion and--if necessary--cut basal metabolism to ensure we can get these calories into our bodies before someone else exhausts them.
For what it's worth, I'm on the other end of the spectrum. My body happily burns away fat stores. This is frankly great in the modern world! But if I get seriously sick (or thrust into a starvation environment), my odds of dying are high--it's why folks with a mid-twenties BMI have a longer life expectancy than those of us closer to twenty. Not techhnically underweight, and with plenty of muscle. But also with less of a buffer.
> human body left alone in a modern supermarket world is way off its original evolutionary envelope
It's arguable that the evolutionary envelope was leapt off around the development of agriculture and animal breeding. (We're still on patch Tuesday from c.a. 10,000 BCE on lactase.)
We have studied hunters and gatherers which survived into recent times and they indeed seem to be very metabolically healthy. "Starvation" is a strong word, but they certainly don't live in a world of plenty and tend to be lean.
What you are describing is so-called "thrifty gene hypothesis", it makes a lot of sense, but it hasn't been corroborated by actual genomic observations yet.
> What you are describing is so-called "thrifty gene hypothesis", it makes a lot of sense, but it hasn't been corroborated by actual genomic observations yet
The problem with thrifty genotype is hunter-gatherers seem to have had less caloric volatility (if we control for habitat quality) [1]. So to the degree such genes might have emerged, it would have had to have been selected for during migrations. That, in turn, requires it be a relatively human-specific adaptation, which frankly makes me sceptical.
The human body left alone in a modern supermarket world is way off its original evolutionary envelope. I am a descendant of 300 generations of agricultural people and I still struggle with processing of milk. Most of our commercially sold foods aren't 300, but 1-2 generations old. We just cannot be adapted to that.