If you eat 1% fewer calories than you burn every day you will die. You will also die if you eat 1% more calories than you burn every day. Is it possible, really, to suggest that the availability of calories was 100% of the daily requirement of our ancestors, and not 99%, or 101%? That is a level of accident that exceeds belief.

It is incredible to think this precise balance could be maintained by anything other than a closed loop of biological control. How would the wheat on a medieval farm know how much to grow each season? If it was off by 1% consistently, everyone would have died... unless they had a mechanism for satiation.

How do you think our microbial ancestors maintained internal salinity, through the limited availability of salt in the ancient ocean?

You will also die if you eat precisely the amount of calories you burn every day.

There exists something called a "feedback loop", something common in biology. You would probably find it interesting, you should look it up.

Basically, it means that if you try to chronically eat, say, 1% more calories than are burned, your body will try to burn more calories to compensate.

I'm not sure I grasp the rest of your comment, could you try again to explain? The wheat farm your ancestors worked did not provide the excess of cheap calories available to the present day American.

> unless they had a mechanism for satiation

It ends up being the opposite. Rather than the body having a satiation response, it controls the metabolism.

If you've ever fasted, you've experienced this. You just don't have the energy to do much other than sit around when you are hungry.

Ancient societies realized this, it's why they'd give out calorie dense meals to their farm labor. For a serf in England, harvest time was often met with a very calorie dense meal. For roman soldiers, they had a diet of meats and cheeses.

I'd also point out that you don't need to have exactly 100% daily calorie intake. You can go a week with just 99% and catch up with 101% the next week just fine.