Longevity testing

VO2 Max: The #1 Longevity Marker You've Never Had Measured

You know your weight. You probably know your blood pressure and your cholesterol. You may even know your body fat percentage from a DEXA scan.

But if you asked most people for the single number that best predicts how long they'll live, almost none of them could give it to you. That number is your VO2 max, and the research behind it is some of the strongest in all of preventive medicine. This post covers what it is, why cardiologists now call it the most powerful predictor of all-cause mortality we have, what your number should be at your age, and how to measure and raise it.

What VO2 max actually is

VO2 max is the maximum amount of oxygen your body can take in, deliver, and use during hard exercise. It's expressed in milliliters of oxygen per kilogram of body weight per minute (mL/kg/min).

Think of it as the size of your engine. It reflects how well your lungs load oxygen, how much blood your heart can pump per beat, how dense your capillaries are, and how many mitochondria your muscles have to burn that oxygen for energy. Every one of those systems is a system that fails with age. VO2 max is the one number that summarizes them all.

The research: fitness beats every traditional risk factor

The study that changed how doctors talk about fitness came out of the Cleveland Clinic in 2018 and was published in JAMA Network Open. Researchers followed more than 122,000 patients who had completed a treadmill test and grouped them by fitness level.

• Low fitness carried a higher risk of death than smoking, diabetes, or coronary artery disease. Being unfit was a bigger risk factor than the conditions we spend billions trying to manage.
• Every step up in fitness lowered mortality. Moving from the bottom 25% of fitness to below-average fitness cut the risk of death roughly in half.
• There was no upper limit. The "elite" fitness group had the lowest mortality of all. The benefits didn't plateau at "good enough."

A 2022 study in the Journal of the American College of Cardiology looked at roughly 750,000 U.S. veterans and found the same pattern: the least-fit group had about four times the mortality risk of the most-fit group, and the relationship held across every age, race, and sex.

Why VO2 max beats body fat, cholesterol, and even smoking

Most risk factors tell you about one pathway to disease. LDL cholesterol tells you about plaque. HbA1c tells you about blood sugar. VO2 max tells you about your reserve capacity across all of them.

As you age, VO2 max declines roughly 10% per decade after 30, and faster after 60. At some point, the everyday tasks of living, climbing stairs, carrying groceries, getting up off the floor, start requiring a large fraction of your maximum capacity. When a task takes 80–90% of your VO2 max, it becomes exhausting, and eventually impossible.

Your VO2 max today determines when that day arrives. A 45-year-old with a VO2 max of 50 has decades of buffer. A 45-year-old with a VO2 max of 28 is already within striking distance of the threshold where independence starts to slip. That's why longevity physicians have made VO2 max the centerpiece of training for your last decade: building enough capacity now that you can still do what you love at 80 and 90.

What's a good VO2 max?

VO2 max norms depend on age and sex. Here are approximate values in mL/kg/min from population reference data:

Estimated vs. measured VO2 max

Your smartwatch gives you a VO2 max number. It's an estimate, derived from heart rate and pace on your runs, and it can be off by 10–15% or more, especially if you don't run, if you're on a beta blocker, or if your training isn't steady-state cardio.

A true VO2 max test is done with a metabolic cart. You wear a mask that measures every breath while you walk, run, or cycle through progressively harder stages until you reach your limit. It takes 10–15 minutes and gives you:

• Your actual VO2 max, measured, not modeled
• Your heart-rate training zones, based on your own physiology instead of a formula
• Your ventilatory thresholds, the points where your body shifts from primarily fat-burning to carbohydrate-burning, which is exactly what you need to train Zone 2 correctly
• Your fat-burning vs. carb-burning profile across intensities

If you're going to build a training plan around a number, it should be a real one.

How to improve your VO2 max

The good news: VO2 max is one of the most trainable markers in your body. Untrained people can improve it by 15–25% in a few months. Here's the protocol the research and the top longevity physicians agree on.

Build the base with Zone 2 (about 80% of your cardio time)

Zone 2 is the easy-conversational intensity, roughly the effort where you can talk in full sentences but wouldn't want to. Three to four sessions per week of 45–60 minutes builds mitochondrial density and capillary networks, which is the foundation VO2 max sits on. Cycling, incline walking, rowing, or jogging all work.

Add one or two VO2 max interval sessions per week

The most studied format is the "Norwegian 4×4": four minutes at a hard effort (about 90–95% of max heart rate), three minutes easy, repeated four times. It's uncomfortable, and it works. Start with 2×4 if you're new to it.

Lift weights

Muscle is where oxygen gets used. Resistance training two to three times per week improves the peripheral side of the VO2 max equation and protects the lean mass that a DEXA scan shows you're keeping (or losing). If you're on a GLP-1, this matters even more; see our guide on why a baseline and follow-up DEXA are non-negotiable on semaglutide or tirzepatide.

Re-test every 3–6 months

Measure, train, re-measure. You can't manage what you don't track, and seeing a real VO2 max number move is one of the most motivating things in fitness.

VO2 max and DEXA: the two numbers that matter most

We think of VO2 max and DEXA body composition as the two halves of a longevity assessment.

• DEXA tells you what you're made of: lean mass, fat mass, visceral fat, and bone density. It tells you whether you're carrying the muscle you'll need and losing the fat that's working against you.
• VO2 max tells you what that body can do: how much capacity your heart, lungs, and muscles have, and how much reserve you'll carry into your 60s, 70s, and 80s.

Together, they answer the two questions that matter for a long, capable life: Do you have the structure? and Do you have the engine? Learn more about what each test measures.

This article is for educational purposes and is not medical advice. Talk to your physician before starting a new exercise program, particularly if you have a history of heart disease. Sources: Mandsager K, et al., JAMA Network Open, 2018; Kokkinos P, et al., J Am Coll Cardiol, 2022; Ross R, et al., AHA Scientific Statement, Circulation, 2016.