Macfadden marketed physical culture as a route to rejuvenation and a longer, more vigorous life. The historian James Stark records that Macfadden promoted a vegetarian diet and periodic fasting as a means of achieving rejuvenation, and that he recast the argument around the new science of vitamins in the early 1920s (Stark 2018). It is classified as testimonial: the supporting evidence was Macfadden’s own physique and longevity narrative and the testimony of followers, not a controlled study with a measured ageing or mortality endpoint. It is recorded as unreplicated because no controlled outcome study established that the regimen slows ageing or extends lifespan. The rejuvenation framing is the life-extension core of the case; the surrogate that does hold (improved fitness from exercise and moderate diet) is recorded separately and does not establish the rejuvenation claim.