Cats (both housecats and big cats) lie around all day, walk a bit, and engage in short, brief runs to attack prey.

Exercise is BS - it's a way to blame sloth for poor diet.

The causality is exactly the other way around - if your diet is poor you will be tired and "lazy", if your diet is good you will have energy to burn.

As to proper diet, I believe paleolithic man had little seasonal food and ate mostly meat. One piece of evidence of this is that where native people do eat plants, the people are highly adapted to local plants and often have complex preparations to de-toxify them. On the other hand we can eat meat more or less however we want.