Is that likely? Per calorie, meat is more expensive, and people weren’t that rich, on average, at the time. Also https://en.wikipedia.org/wiki/Ancient_Roman_cuisine states: John E. Stambaugh writes that meat "was scarce except at sacrifices and the dinner parties of the rich."

Also, gladiators may have been loading carbs to gain a protective layer of fat. https://archive.archaeology.org/0811/abstracts/gladiator.htm...:

”Gladiators, it seems, were fat. Consuming a lot of simple carbohydrates, such as barley, and legumes, like beans, was designed for survival in the arena. Packing in the carbs also packed on the pounds. "Gladiators needed subcutaneous fat," Grossschmidt explains. "A fat cushion protects you from cut wounds and shields nerves and blood vessels in a fight." Not only would a lean gladiator have been dead meat, he would have made for a bad show. Surface wounds "look more spectacular," says Grossschmidt. "If I get wounded but just in the fatty layer, I can fight on," he adds. "It doesn't hurt much, and it looks great for the spectators."”