After spending a week watching the Starz hit Spartacus, I was curious to find out if Gladiators were actually in incredibly ripped shape and what they ate if that were the case. It turns out that Gladiators were called Barley Men. They ate a primarily vegetarian diet that was in no way similiar to the normal free living inhabitants they entertained. They ate no animal protein but mostly barley and legumes for the purpose of gaining weight. A gladiator who was overweight was able to be cut and bleed more while being able to continue fighting. If a gladiator was lean and cut it would have cut into muscle and the chance of the gladiator being able to continue was greatly reduced. So in a recap, a vegetarian high grain, high legume diet was used to fatten them up!
To read into more detail the archeological article is located here