Fletcher held that his regimen restored youthful vigour, the framing captured in the subtitle of his 1913 book, “How I Became Young at Sixty.” The supporting evidence was his own case and a set of gymnasium tests at Yale, where at fifty-eight he was reported to perform feats of strength and endurance with unusual ease. It is classified as testimonial: the demonstration centred on a single self-selected subject, the promoter himself. It is recorded as unreplicated because the tests were uncontrolled exhibitions rather than a controlled study, and no controlled replication established that the regimen confers extraordinary vigour or slows ageing. Chittenden’s 1904 work, which observed Fletcher among its subjects, demonstrated that fitness was compatible with a low protein intake; it did not demonstrate that mastication makes an old man young.