What is VO2max and how important is it for living longer?
A higher VO2max is strongly associated with a longer lifespan. Regular physical activity pays off for everyone, even if you currently train very little: even modest effort noticeably reduces the risk of premature death.
VO2max is the maximum amount of oxygen your body uses per minute during intense exercise, expressed per kilogram of body weight. It is the gold standard for cardiovascular and pulmonary fitness: the better your heart, lungs and muscles work together, the higher the score. In practice it is also expressed in METs, a simpler measure of exercise capacity.
The link with a longer life is one of the strongest in health science. A meta-analysis of 33 studies involving more than 100,000 participants found that each step up in fitness (1 MET) reduces the risk of death by an average of 13%. People with poor fitness have a 70% greater chance of dying prematurely than people with good fitness. That is a larger effect than for many other well-known risk factors.
The Copenhagen Male Study followed men for 46 years. Men with a high VO2max in middle age lived an average of 4.9 years longer than men with the lowest fitness levels. Every one-unit improvement was associated with 45 extra days of life. They also died from cancer less frequently, even after correcting for reverse causality.
One study does, however, put this picture into perspective. Research using genetic variants to test causality found no evidence that VO2max itself extends lifespan. VO2max is most likely a reflection of underlying factors such as body fat, muscle mass and physical activity behaviour. Genetically higher body fat demonstrably lowers VO2max in a causal way. Body fat and diabetes were, in that same study, independently and causally associated with a shorter lifespan.
The good news is that you do not need to be a top athlete to benefit. Even light physical activity, calibrated to what feels strenuous for you personally, noticeably reduces the risk of cardiovascular disease and premature death. This was shown in research involving women with an average age of 78.5 years. Even if you currently train very little, modest efforts already pay off.
Based on a meta-analysis (33 studies, more than 100,000 participants), the Copenhagen Male Study (46 years of follow-up), a study using genetic variants that found no causal effect of VO2max on lifespan, and an observational study in older women. All associations are observational, except for the genetic evidence, which in fact demonstrates no causal effect.