I'm looking it thus way... Humans throughout our history ate local seasonal food. They moved a lot and they eat just right or too little and you would not see one fat person in a village. In the old days, only kings were these fat creatures sitting on their throne not doing much.
Nowdays we all can became kings quite easily.
We ate fruits in the season to build up fat before winter. Nowadays, the season never ends.
On top of that, we're manufacturing foods made from sugar and oil with very little protein, and sugar drinks replaced water.
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.
