That’s one of the questions Peter Attia MD explores in Outlive: The Science and Art of Longevity.
The answer is a technical one: Peak aerobic cardiorespiratory fitness, measured in terms of VO2 max.
So what exactly is VO2 max? It is the maximum rate at which we can utilize oxygen. The more oxygen our bodies are able to use, the higher our VO2 max.
And how is VO2 max measured? “While a person is exercising at essentially their upper limit of effort,” Peter writes. And then he adds: “If you’ve ever had this test done, you will know just how unpleasant it is.”
Because, eventually, we reach a place where we just can’t produce any more energy via oxygen-dependent pathways.
At that point, we “are forced to switch over to less efficient, less sustainable ways of producing power,” Peter writes. “The amount of oxygen that I am using at this level of effort represents my VO2 max.”
Shortly after reaching that point, we “fail,” which means we can no longer keep running up the hill at that pace.
The higher our VO2 max, the more oxygen we can use, and the faster we can ride or run. Or do whatever it is we want to do.
2: Our VO2 max is a good gauge of our overall physical capability. “It tells us what we can do,” Peter notes, “and what we cannot do.”
Two things stand out when we look at data that charts low, average, and high VO2 max levels by age:
“First,” he writes, “there’s a huge gap in fitness between the top and bottom 5 percent of each age group (the upper vs. lower lines).
“Second, it’s striking how steeply VO2 max declines with age, and how this decline corresponds to diminished functional capacity. The lower it goes, the less you can do.”
An average thirty-five-year-old male with a VO2 max in the mid-30s can typically run a mile at a ten-minute mile pace.
So how does this compare with a typical male at age seventy? Only the most fit 5 percent of people will still be able to do this.
There are similar results for other activities: “An average forty-five- to fifty-year-old will be able to climb stairs briskly (VO2 max = 32), Peter notes, “but at seventy-five, such a feat demands that a person be in the top tier of their age group.
“Activities that are easy when we are young or middle-aged become difficult if not impossible as we get older. This explains why so many people are miserable in their Marginal Decade. They simply can’t do much of anything.”
3: An elite endurance athlete often scores in the high 60s and above. However, “this number is not just relevant to athletes,” Peter notes.
“It turns out to be highly correlated with longevity,” he explains. “A 2018 study in JAMA that followed more than 120,000 people found that higher VO2 max (measured via a treadmill test) was associated with lower mortality across the board.
“The fittest people,” he explains, “had the lowest mortality rates—by a surprising margin.”
A typical male, age forty-five, will have a VO2 max of around 40 ml/kg/min. An out-of-shape person in their thirties or forties might score only in the high 20s on a VO2 max test, says Mike Joyner, an exercise physiologist and researcher at the Mayo Clinic.
What does this level of fitness translate to? “They simply won’t be able to run up that hill at all,” Peter observes.
“Consider this,” he writes: “A person who smokes has a 40 percent greater risk of all-cause mortality (that is, risk of dying at any moment) than someone who does not smoke, representing a hazard ratio or (HR) of 1.40.
“This study found that someone of below-average VO2 max for their age and sex (that is, between the 25th and 50th percentiles) is at double the risk of all-cause mortality compared to someone in the top quartile (75th to 97.6 percentiles).”
That’s right: not being fit is more likely to kill us than smoking.
“That’s only the beginning,” Peter notes. “Someone in the bottom quartile of VO2 max for their age group (i.e., the least fit 25 percent) is nearly four times likelier to die than someone in the top quartile—and five times likelier to die than a person with elite-level (top 2.3 percent) VO2 max. That’s stunning.”
But we don’t have to be an elite athlete to benefit: “Even just climbing from the bottom 25 percent into the 25th to 50th percentile ( e.g., least fit to below average),” he writes, “means you have cut your risk of death nearly in half, according to the this study.”
In 2022, the American College of Cardiology published a much larger study examining data from 750,000 US veterans ages thirty to ninety-five.
“This was a completely different population that encompassed both sexes and all races,” Peter notes, “yet the researchers found a nearly identical result: someone in the least fit 20 percent has a 4.09 times greater risk of dying than a person in the top 2 percent of their age and sex category.
“Even someone of moderate fitness (40th to 60th percentile) is still at more than double the risk of all-cause mortality than the fittest group, this study found.”
The JAMA study researchers conclude: “Extremely high aerobic fitness was associated with the greatest survival. . . Cardiorespiratory fitness is inversely associated with long-term mortality with no observed upper limit of benefit.”
No. Observed. Upper. Limit. Of. Benefit.
The really good news? VO2 max can be increased via training.
More tomorrow!
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Reflection: How’s my overall level of fitness? Does the data on longevity excite or concern me?
Action: Discuss with a friend or colleague.