Is VO2max overrated? Fitness, body fat and longevity

VO2max has become a favourite number in the longevity world, promoted by podcasters, wearable makers and doctors alike. That popularity has triggered a backlash: is a single number really that important, or is it partly a proxy for being lean, young and healthy? Both sides have a point. Here is a balanced look at the evidence.

The case for VO2max

The evidence that cardiorespiratory fitness predicts survival is large and consistent.

• Mandsager et al. (2018) followed 122,007 patients after a treadmill test at Cleveland Clinic. Risk of death fell steadily with each step up in fitness, the least fit had roughly five times the risk of the elite group, and there was no upper limit of benefit.
• Kodama et al. (2009) pooled 33 studies and found that each 1-MET (3.5 ml/kg/min) higher fitness was linked to about 13% lower risk of death from any cause.
• Weeldreyer et al. (2025), a meta-analysis in the British Journal of Sports Medicine of 20 studies and 398,716 observations, found that fit people with overweight or obesity had no statistically significant increase in all-cause or cardiovascular mortality compared with fit people of normal weight. Unfit people, at any BMI, had roughly two to three times the risk.

That last finding updates the older fit-but-fat research and suggests fitness blunts much of the mortality risk linked to a high BMI.

The case that it is overrated

It is observational

None of these studies can prove that raising your VO2max will extend your life. Fit people differ in genes, income, diet and undiagnosed illness. Low fitness can be a result of disease, not only a cause. See VO2max and longevity for how researchers handle this.

Part of it is genetic

In the HERITAGE Family Study (Bouchard et al., 1999), the response to the same training programme varied widely and clustered in families. Some people gain a lot from training; others gain little. More in VO2max trainability.

It is partly a body-composition score

VO2max is usually divided by total body weight. Fat consumes little oxygen during exercise, so extra fat lowers the number even if your heart and muscles are unchanged. Imboden et al. (2020) studied 2,905 adults who had a lab exercise test and a body-fat measurement. Fitness expressed per kilogram of fat-free mass was linked to all-cause, cardiovascular and cancer mortality, and predicted all-cause mortality better than fitness per kilogram of body weight. In other words, part of what "VO2max per kilogram" captures is simply leanness. See VO2max and body weight.

Other things predict survival too

Higher muscle strength is also linked to lower mortality: a meta-analysis of data from about 2 million adults found this association (García-Hermoso et al., 2018). So is daily movement: a meta-analysis of 15 cohorts found that more daily steps were associated with progressively lower risk of death, levelling off at a moderate step count that depended on age (Paluch et al., 2022).

What VO2max actually reflects

Factor	How it affects VO2max	Can you change it?
Genes	Sets baseline and trainability	No
Age	Declines over the decades	No, but training slows the drop
Training and activity	Raises it within weeks	Yes
Body fat	Lowers the per-kg value	Yes
Muscle mass	More muscle can use more oxygen	Yes
Heart, lung and blood health	Disease lowers it	Partly

VO2max is best seen as a summary marker: it bundles heart function, blood, muscle, body composition, activity habits and underlying health into one number. That is exactly why it predicts outcomes so well — and why it should not be treated as the only target. See what limits VO2max for the physiology.

So, is it overrated?

Not as a marker. It remains one of the strongest single predictors of mortality, and unlike genes or age, the modifiable parts respond quickly to training. It is overrated if it becomes the only goal: chasing a higher watch estimate while ignoring strength, sleep, diet, blood pressure or smoking misses most of the picture. Watch estimates also carry error; see how accurate watch VO2max is.

What to do

1. Measure it, then compare it fairly. Use the VO2max calculator and the norms by age and sex, and check your fitness age.
2. Aim to leave the bottom group. The biggest risk differences are between unfit and moderately fit.
3. Train strength twice a week as well as aerobic fitness.
4. Move every day — steps count.
5. Track body composition and health markers, not only VO2max. Browse more studies on our research page.

If you have a health condition or have been inactive, talk to your doctor before starting vigorous exercise.

Sources

• Weeldreyer NR, et al. Cardiorespiratory fitness, body mass index and mortality: a systematic review and meta-analysis. Br J Sports Med, 2025.
• Mandsager K, et al. Association of cardiorespiratory fitness with long-term mortality among adults undergoing exercise treadmill testing. JAMA Netw Open, 2018.
• Kodama S, et al. Cardiorespiratory fitness as a quantitative predictor of all-cause mortality and cardiovascular events in healthy men and women: a meta-analysis. JAMA, 2009.
• Imboden MT, et al. Cardiorespiratory fitness normalized to fat-free mass and mortality risk. Med Sci Sports Exerc, 2020.
• Bouchard C, et al. Familial aggregation of VO2max response to exercise training: results from the HERITAGE Family Study. J Appl Physiol, 1999.
• García-Hermoso A, et al. Muscular strength as a predictor of all-cause mortality in an apparently healthy population: a systematic review and meta-analysis of data from approximately 2 million men and women. Arch Phys Med Rehabil, 2018.
• Paluch AE, et al. Daily steps and all-cause mortality: a meta-analysis of 15 international cohorts. Lancet Public Health, 2022.