[SamPatt]

Quoting from his (Jim Fixx) wiki article:

In 1986 exercise physiologist Kenneth Cooper published an inventory of the risk factors that might have contributed to Fixx's death.[6] Granted access to his medical records and autopsy, and after interviewing his friends and family, Cooper concluded that Fixx was genetically predisposed—his father died of a heart attack at 43 after a previous one at 35,[7] and Fixx himself had a congenitally enlarged heart—and had an unhealthy life: Fixx was a heavy smoker before beginning running at age 36, had a stressful occupation, had undergone a second divorce, and gained weight up to 214 pounds (97 kg).[8] Medical opinion continues to uphold the link between moderate exercise and longevity.[9]