http://index.hu/mindekozben/poszt/2017/03/28/russell_crowe/

Recent research on Gladiator tombs in present day Turkey indicate that the fighters may have been on vegetarian diets, that likely consisted of grains and beans that would increase their body sizes around their abdomens. This essentially added a layer of body fat and muscle to protect their internal organs when stabbed or sliced. Some murals depict gladiators with literal barrel-like chests. 
http://www.imdb.com/title/tt1442449/trivia?item=tr1420950