I’m talking about before we figured out we could grow vegetables and fruits. Early humans are often shown as being fit and in shape, yet our diet pretty much only consisted of meat. We were hunters. So why the hell were they so fit? I thought a healthy diet mattered more than just being active constantly?
Probably because meat was only a small fraction of their diet.
Most cavemen were foragers, they would also fish, and look for a lot of things that were edible. Wild fruits and berries, roots, primitive plants ancestors of the ones that are now cultivated, etc.
Meat meant hunting, and hunting was dangerous, long and difficult. After a while, they would move on once game got rarer.
So, no, meat was not their only source of food.