The daily food of the Greeks consisted of bread or corn-porridge with a side-dish, e.g. olives, fresh vegetables, dried figs or cheese. The most important source of proteins was fish. Meat was eaten only occasionally, mostly at feasts after a sacrifice.
In order to perform properly, athletes had to take in enough proteins to make their muscles grow. Because athletes were mostly rich, they could afford more expensive food than others. Most athletes ate a lot of meat. The philosopher Pythagoras, who was probably himself a vegetarian, is told to be the first to advise this diet. Some famous athletes from Southern Italy, e.g. Milon, were Pythagoreans. From sweets, however, the athletes had to abstain.
Many intellectuals, e.g. Euripides, criticized the eating habits of athletes and depicted them as gluttons. There was a story that Milon and Theagenes ate a whole bull in a single day. The criticism mainly addresses athletes from the combat sports. Because there were no weight-categories, heavyweights had a clear advantage, as in Japanese sumo-wrestling. Runners on the other hand were not in the right shape for the contest if they ate too much. The criticism of athletes might be partly due to envy, because most Greeks did not have so much good food at their disposal.