I think it depends what you mean by citizens, Joe. There were slaves and masters, shopkeepers, tradesmen, nobles, prostitutes, soldiers, etc., etc. - and they had to make a living. If you only count people who had no need to work - the well-off - then that's a different matter. From watching Mary Beard's UK TV programmes on Rome (she's a university professor specialising in the topic), it seems that the well-off had cooks and would probably eat at home.

Rome, it appears, was absolutely stuffed with street food and eating places - fast food everywhere - where anyone could pay for a meal or a snack. A bit like a Bangkok street market!

It's possible that your tour guide was exaggerating slightly.