If walking is good for one's health, the postman would be immortal.

A whale swims all day, eats only fish, drinks lots of water but it is fat!

A rabbit runs and hops all day long but lives only, at best, for 15 years.
In comparison, a turtle doesn't run. It does nothing literally yet can live for 200 years.

So why do people want to exercise?
Just eat and sleep well. And be a happy person!