Obviously, Domery was suffering from some sort of medical condition. The problem is that we aren’t sure what it was. It’s hard to diagnose someone who lived over two hundred years ago based on the sort of limited evidence we have for Domery’s condition, but some have suggested that he suffered from hyperthyroidism, a condition caused by the overproduction of thyroid hormone. The accounts of the doctors studying Domery might actually support this theory. After all, Domery sweat profusely, had trouble sleeping, and ate constantly but never seemed to gain weight, all symptoms of hyperthyroidism.
But there are also a number of problems with this theory. If Domery suffered from hyperthyroidism, then his story suggests that it was one of the extreme forms of the condition in history. There’s no modern case of hyperthyroidism doctors can point to where the patient went around eating grass, cats, and candles. In addition, Domery lacked many of the other symptoms of the condition like mood swings, anxiety, or a rapid heartbeat. This doesn’t disprove the theory that Domery was suffering from hyperthyroidism, but it does mean that if he was then it was a very strange case of the condition.
But there’s the possibility that Domery’s story was exaggerated. The only real sources available for his life come from the testimony of the soldiers and doctors in the prison where he was held. It’s possible that these stories were exaggerated or corrupted in retellings. It’s worth noting that Domery probably wasn’t even the man’s name. “Charles Domery” is distinctly English and would be a strange name for a Polish man to have. The fact that his name wasn’t recorded correctly means that other elements of his story may be embellished or mistranslated by the doctors as well.
But Domery almost certainly existed. The doctors examining him took careful notes of his habits and vital signs. It would be very unusual for two established medical professionals to completely invent the story and create meticulous notes to support it. And that means that Domery definitely had an abnormally large appetite. Why else would the doctors have been dispatched to examine him? If some parts of Domery’s story are exaggerated, then they probably came from the French soldiers who testified about his extreme behavior to his doctors. It’s easy to imagine some bitter French prisoners of war deciding to have some fun at the expense of their captors by telling them Domery used to eat grass.
If you discount the more fantastic elements of Domery’s story, the picture that emerges is closer to someone suffering from a normal medical condition that caused extreme hunger. Hyperthyroidism is a closer fit for this picture, and some have even proposed that the answer could be damage to Domery’s brain. Ultimately, Domery disappeared from the historical record after the visit from the doctors. So, we simply don’t know much more about him than they recorded. And that means that most likely, Domery and his legendary appetite will remain a mystery. But it’s certainly one that makes for a great story.