Comment by cthalupa

> which strikes me as pretty ample unless they're also adding a bunch of physical activity.

It seems likely we've evolved to reduce energy expenditure in other ways when we regularly induce physical activity, too. Walk 20,000 steps or spend a couple of hours on the treadmill? Your body finds ways to reduce your energy expenditure elsewhere.

https://pmc.ncbi.nlm.nih.gov/articles/PMC4803033/