How about Roman and Byzantine (Costantinople) cities, where bread was distributed for free each day to every one in the city?
And both Rome and Byzantium suffered large population declines during some of their history.
Other counter-examples include medieval Europe, where average life expectancy was 60+ and they worked less hours than present-day Americans.
Production of products back then wasn't too advanced. Many of the slaves had the experience and skills to contribute to a specific value chain of these empires. Using bread as an example, in their culture the slaves had experience baking and farming. The only difference is they aregoing to do it for free and the stuff they produce will go to their rulers. Any problems with that, you can get murdered.
http://en.wikipedia.org/wiki/Life_expectancy#Life_expectancy...
For example, these rich cities frequently had to defend themselves against the poor and hungry. Being sacked was a common occurrence. It's a recent convenience (over the past few hundred years) that cities aren't surrounded by walls.