In the 1930s, White Castle owner Edgar Waldo "Billy" Ingram was obsessed with proving, for once and for all, that hamburgers were healthy. Ingram looked to science for proof, enlisting the help of Jesse McClendon, Ph.D. 

Dr. McClendon initiated The White Castle Project after finding a med student willing to eat nothing but tiny-ass hamburgers for 13 weeks straight. Bernard Flesche kept to the regimen, eating White Castle and drinking water for 91 days. After that triumphant last day, Flesche became an integral part of the chain's ad campaign, which was fixed around the claim that a person "could eat nothing but [White Castle] sandwiches and water, and fully develop all physical and mental faculties."

Flesche never willingly ate a burger again, and died at the age of 54 from heart problems.

[via Gothamist]