In my own (somewhat humble) opinion, articles like these get the headline and angle completely wrong. It's backwards.

Animals' natural state, including humans', is lots of exercise. This is the default; it is what our bodies and brains are adapted to doing.[-]

A result like this demonstrates that a lack of exercise is harmful. Failure to exercise inhibits the brain from functioning properly as it is adapted to doing.

[-] "Nothing in biology makes sense except in light of evolution." -- Dobzhansky