It was my understanding, from reading several threads on this sub, that muscles seen by Vikings and gladiators in TV and movies aren't historically accurate. Muscles like that come from modern weight lifting and nutrition.
But classical statues show really defined muscles that require diets better than what any of them had. Would have nobles been able to get that? Or is there another reason for this discrepancy?
Most men in ancient Rome and Greece had to go though military training, and that would indeed lead to the physiques you see in status, at least in some cases. Also, obesity was not nearly as common as it is today, since food was not so abundant and many people relied on manual labor on a daily basis.
Just as models in today's magazines and ads, sculptors would choose only the fittest to model for their sculptures. That body definition was a goal, rather than a norm.
It is safe to say that common people, especially older, didn't have perfect physiques; although on average they were probably fitter than many people today in western and rich countries. Yet, it is likely that a good number of young people, especially after military training, would have exhibited excellent bodies.