Does the Most Famous 'VO2 Max Study' Actually Measure VO2 Max?
Does the Most Famous VO2 Max Study Actually Measure VO2 Max?
If you follow the health and longevity space, you’ve probably seen Peter Attia’s name in the news lately, and not for his research. Following the DOJ’s release of the Epstein files in January, Attia’s name appeared in over 1,700 documents showing a friendly correspondence with Jeffrey Epstein over several years. He’s since issued a public apology, describing the emails as “embarrassing, tasteless, and indefensible,” and has faced significant professional fallout as a result.
I get why people are questioning his judgment. The scrutiny is both warranted and self-inflicted.
But what I've noticed is people using this as a reason to throw out everything he's ever said about health and longevity, and that's where I'd push back. Not to defend the man, but to defend the science. A study's validity doesn't depend on who promotes it. So let's actually look at this one on its own merits.
The Study Everyone Quotes
If you’ve read Outlive or listened to Attia’s podcast, you’ve heard him reference Mandsager et al. (2018), published in JAMA Network Open. It’s also a study I’ve been sharing for years through my Living Proof Challenge — a free challenge that thousands of people complete each year — because the findings are that compelling.
The study is massive: over 122,000 patients, examining the relationship between cardiorespiratory fitness and all-cause mortality. What it found is striking. Higher fitness is associated with dramatically lower risk of death, with a clear dose-response relationship across the entire fitness spectrum. And crucially, the benefit doesn’t plateau at the top. Being in the “Elite” fitness category (top 2.5%) was associated with meaningfully better outcomes than simply being “High” fit. There’s no ceiling here. The fitter you are, the better.
Some critics have pushed back, not on that conclusion, but on a technical point worth addressing.
The METs vs. VO2 Max Distinction
Here’s the thing: Mandsager didn’t actually measure VO2 max. The study estimated exercise capacity in METs (metabolic equivalents of task) derived from a treadmill test. There was no metabolic cart, no direct measurement of oxygen consumption. One MET is roughly 3.5 mL of oxygen per kilogram of body weight per minute, so METs and VO2 max are mathematically related and highly correlated, but they’re not identical.
So when Attia and others describe this as a “VO2 max study,” that’s technically imprecise. Treadmill-estimated METs carry measurement error, and the conversion equations don’t hold equally for everyone.
Is this a fair criticism? Yes, if you’re being scrupulously precise.
Does it change the fundamental message? Not really. METs and VO2 max are measuring the same underlying physiological system: how effectively your heart, lungs, and muscles deliver and use oxygen. They correlate at around r = 0.85 to 0.90 in most populations. The finding that people with greater aerobic capacity live longer, with a steep penalty for being unfit, is not undermined by the fact that METs were used instead of a directly measured VO2 max. Being technically right about the measurement tool while dismissing the core message isn’t the win the critics seem to think it is.
The Criticisms That Actually Matter
If you want to find legitimate limitations in how this research is presented, I’d point you in two directions.
First: accessibility.
Attia’s practical framework around VO2 max is expensive. A proper lab-based VO2 max test runs anywhere from $150 to $400 depending on where you are. Add coaching, lactate testing, power meters, structured training blocks, and you’re looking at a longevity approach that realistically applies to a fairly narrow slice of the population.
What I’ve never heard Attia discuss, and this genuinely surprises me, is the fact that free, well-validated alternatives have existed for decades. You don’t need a sports performance lab to get a meaningful estimate of your cardiorespiratory fitness.
The Rockport Walking Test. A flat 1-mile course, a watch, and a way to measure your heart rate at the end. Walk as fast as you can, plug your numbers into a simple equation, and you have a reasonable VO2 max estimate. Completely free.
The Cooper 12-Minute Run Test. Developed by Dr. Kenneth Cooper in the 1960s for the U.S. military. Run as far as you can in 12 minutes, measure the distance, and look up your score on a reference table. Decades of validation data exist across age groups and populations.
The Beep Test (20m Progressive Shuttle Run). Used in schools, military programmes, and sports academies globally because it requires almost nothing and can be done anywhere. An audio track plays progressively faster pacing tones; you run between two lines 20 metres apart until you can’t keep up. And it’s not just convenient, it’s genuinely accurate. A 1988 study by Ramsbottom, Brewer, and Williams published in the British Journal of Sports Medicine directly measured VO2 max in 74 volunteers and found a correlation of r = 0.92 with shuttle run performance. That’s an exceptionally strong correlation, stronger than many clinical tools used in practice every day. A free test you can do in a park is giving you information that closely tracks what a lab would tell you.
Now, someone could try to estimate their own METs based on their weekly activity, and there’s nothing wrong with that as a starting point. But here’s the problem: it’s very easy to overestimate how much you actually do and how hard you actually work. We’re all guilty of it. A field test removes that bias entirely. When you’re running the beep test or the Cooper run, your body sets the limit. You simply cannot perform beyond your actual cardiorespiratory capacity. The test finds your ceiling for you, whether you like the answer or not.
Low cardiorespiratory fitness is disproportionately prevalent in lower-income populations, the very people least likely to have access to a sports performance lab. If the message is “VO2 max may be the most powerful longevity predictor we have” but the practical guidance assumes you can afford premium testing and elite coaching, you risk making the whole conversation feel irrelevant to the people who need it most. That’s worth naming.
Second, and this is the one I find more interesting: the study’s own methodological limitations.
The Mandsager paper is observational, not interventional. It shows association, not causation. That’s a standard and important caveat. But there’s a more specific issue that doesn’t get discussed enough: in the multivariate analysis, the authors did not adjust for key cardiometabolic risk factors including diet quality and alcohol consumption.
Why does that matter? Because people who exercise more tend to eat better and drink less alcohol. These behaviours cluster together. So when we observe that fitter people live longer, we can’t cleanly separate the effect of fitness itself from the effect of the healthier lifestyle that tends to accompany it. Some portion of the survival benefit attributed to cardiorespiratory fitness may actually be driven, at least in part, by dietary patterns and alcohol intake that the analysis never accounted for.
This doesn’t invalidate the finding. Cardiorespiratory fitness is almost certainly genuinely protective, and the consistency of the dose-response relationship across a dataset of 122,000 people is hard to dismiss. But it does mean we should hold the effect size with some humility.
And here’s where I think it’s worth raising an eyebrow. Peter Attia has been one of the most vocal critics of observational nutritional epidemiology, frequently and rightly pointing out that studies showing associations between diet and health outcomes fail to adequately control for confounders, suffer from measurement error, and can’t establish causation. Those are fair criticisms. But applying that same rigorous lens to a study he relies on heavily would require acknowledging that Mandsager has some of the same limitations. The confounding variables that make dietary observational data messy, things like lifestyle clustering, unmeasured behaviours, and residual confounding, apply here too. You can’t hold nutrition research to a high methodological bar and then wave away the same issues when they appear in research that supports your other positions. That’s a double standard, and it’s worth pointing out.
The Bottom Line
Let me be clear about what I’m not doing here: I’m not defending Peter Attia’s conduct or his judgment in his personal life. Those are fair targets for scrutiny.
What I am defending is the use of this research to encourage people to move more and build their aerobic fitness. Because that message is well-supported, it’s important, and it doesn’t belong to any one person. The Mandsager study, despite its limitations, is part of a large and consistent body of evidence showing that cardiorespiratory fitness is one of the most powerful predictors of how long you live. Throwing that out because of who’s been citing it would be a genuine public health loss.
Does the study measure METs rather than VO2 max? Yes, and technically that matters, though not enough to change the core conclusion. Does it have real methodological limitations that deserve acknowledgment? Absolutely, especially the failure to adjust for diet and alcohol, which is a significant oversight in any study making claims about lifestyle and longevity. Should the conversation about VO2 max include free testing options accessible to everyone, not just people who can afford a performance lab? Without question.
The science here is strong enough to stand on its own. It doesn’t need a perfect messenger. And the takeaway, that your aerobic fitness matters enormously, and that you can assess it today for free, is one worth getting into as many hands as possible.
Want to learn how to estimate your VO2 max for free and understand what your score means for your long-term health? Check out the Living Proof Challenge.