If one area of longevity research has unusually strong evidence, it is this one. Fitness and muscle mass predict outcomes better than any supplement.
Cardiorespiratory fitness, usually measured as VO2 max, is one of the strongest predictors of all-cause mortality in the epidemiological literature - stronger than smoking status in several large cohorts. Muscle mass and strength track closely behind it. That makes this the one corner of longevity where the evidence is robust enough that the honest advice is boring: build aerobic capacity, keep lifting, eat enough protein.
The guides below cover both halves. On the aerobic side: what VO2 max actually measures, why it declines with age, and how zone 2 training and intervals each contribute to raising it. On the muscle side: why sarcopenia begins decades before most people notice, why planned resistance training beats simply staying active, and how much protein the trials actually support after 40 - alongside the opposite case, protein restriction, which has real animal evidence and a much more complicated human picture.
Two free calculators sit in this topic as well, for fitness age and protein needs. They are estimates built from published formulas, not diagnostics. Every guide cites its sources and follows our editorial policy, and none of it replaces advice from a clinician or a qualified coach, particularly for anyone starting training after a long gap or with an existing condition.
Related topics: GLP-1 and metabolic drugs · Longevity supplements · Longevity science, basics and biological age
VO2 max predicts long-term mortality more strongly than cholesterol. What 122,000 patients and 20 million observations show — and how to raise it.
VO2 max is the fitness number most tied to how long you live — and you can train it. Here's how Zone 2 cardio and intervals work, and how fast it improves.
New research says structured exercise, not just staying busy, protects aging muscle. Here's how to prevent muscle loss with age, backed by real science.
After 40, muscle resists protein's anabolic signal just as many people eat less of it. What the research says on how much, when, and why lifting matters.
A July 2026 review of 350+ studies says less protein may slow aging. What the evidence actually shows — and the age where the advice flips.
Estimate your VO2max without a treadmill test and find your fitness age — the age your fitness really matches. Free, science-based, no sign-up required.
Free protein calculator: your daily target in grams from weight, age, activity and goal. Plus how much protein per kg, and why it rises with age.
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