The practice of throwing up after a meal is actually older than Hollywood and photographic airbrushing techniques, although Julius Caesar's attached psychological issues may have varied slightly from those of young women today. From accounts such as Cicero's, which explained how Caesar escaped an assassination attempt by vomiting after dinner in his bedroom instead of in the bathroom where his assassins expected him, it seems this sort of practice was common enough in Rome that no one batted an eye. Then again, so was watching a prisoner and a bear fight to the death for fun.
Now, people keep quoting "fun facts" about how ancient Romans threw up so much that they had special rooms to do it in, called "vomitoriums." Not so. While they did vomit a lot, and they did have rooms called vomitoriums, they were actually unrelated. Vomitoriums were just hallways in large stadiums where people exited all at once (so they "vomited" people out onto the streets when the event was over). Although, if they had just come out from watching a bear tear a man's arms off, they might have actually vomited in the vomitorium, but that would just be coincidence.
The idea is straightforward enough--to get rid of the food before you have time to digest it and turn it into fat. In the context of the Romans, they seemed to really enjoy eating and thought of it as a way to make room for more. They were type-A, impatient people who had a continent to conquer and couldn't bother with waiting for it to go out the other end.
By now most people are aware of the health consequences of repeated vomiting. But, just for the record, it causes tooth decay, osteoporosis, heart problems, kidney problems, damage to the esophagus, and fainting from low blood pressure. You know how when you throw up, it sort of feels like you're dying? That's your body trying to tell you something. Despite that, people still do it and we call it bulimia.