A gourmand is someone obsessively and unhealthily devoted to eating good food and lots of it.
In Monty Python's film "The Meaning of Life," there is a character who literally explodes after eating just one more mint after a big meal. Well, that in a nutshell is a gourmand. Gourmand is not to be confused with gourmet. A gourmet is a connoisseur of good food who enjoys eating but doesn't do so to excess. A gourmet might find himself full in his favorite restaurant, but he would never explode. Both words are from the Medieval French term gourmant, meaning "glutton."