This is the central life-extension claim of the macrobiotic programme. In the English edition it is the move from “vital consumption inseparable consequence of vital operation” to the “retardation of vital consumption” and the “possibility of prolonging life.” The claim is classified as untested because no controlled human outcome study of the regimen’s effect on lifespan was ever conducted; the evidence Hufeland offered was the posited vital-force mechanism, physiological reasoning, and longevity anecdote (chiefly the spare diet of Luigi Cornaro). That evidence is insufficient to attribute any lifespan effect to the regimen, and it is labelled insufficient here. Two qualifications are recorded for accuracy. First, the mechanism on which the claim rests (husbanding a finite vital force) is separately refuted (see vital-force-determines-lifespan). Second, several of the hygienic components the regimen prescribes (moderation, sleep, physical activity, clean air) overlap with measures that later preventive medicine has associated with health, but those measures do not act by conserving a vital quantity, and that later overlap is not a confirmation of the claim as Hufeland framed it.