What are some big signs of bulimia in a fifty year old?

Age independent. Bulimia doesn't vary with age. It consists of ingesting excessive calories and "compensating" by getting rid of them (purging) through vomiting or laxitive use. Occasional binge eating is not bulimia. Recurrent binge eating without prugring does occur too; it is one form of morbid obesity.
Secrecy. Bulimia is an eating disorder mostly characterized by "secrecy" it is sometimes the result of "failed" anorexia.The patient is shamed by the inability to control intake of food due to extreme hunger in bulimia the mechanism that usually is present that regulates hunger is absent.- no longer perceived by the patient. The patient feels "incomplete" and "worthless" not being able to "control" self.