13. Jared Leto - Chapter 27 (2007)
Previously playing the heroin chic trimness of Harry Goldfarb, Jared Leto packed on the pounds for his portrayal of human filth Mark David Chapman in the 2007 film Chapter 27. Reporting to have sustained a diet which was high in ice cream mixed with olive oil and soy sauce (disgusting), Leto gained 60 pounds to portray the famed assassin. After filming wrapped, Leto immediately dropped the weight back off, looking like his normal self again shortly after. Leto himself claims that he lost 20 pounds within a week after quitting the disgusting diet he'd been on.