Peter Attia

This includes cholesterol.

This includes BMI, smoking.

It even includes age, which just blows my mind.

So cardiorespiratory fitness, CRF, represents how efficiently your heart and lungs and blood vessels and muscles can work together to deliver and utilize oxygen.

So the more efficient that system is, the more physiologic reserve your body has.

And it's this reserve that allows you to tolerate stress.

This stress can come in the form of an infection, a surgery, or just, frankly, the day-to-day demands of living.

This has been most typically and most repeatedly measured using a test called VO2 max.

You've heard me talk about this of course, and it's become a very popular thing that people talk about.

It's the maximum rate at which the body can utilize oxygen, tested of course during maximal efforts which require exercise.

So this number is expressed in milliliters of oxygen per kilogram of body weight per minute.

But it can be estimated using something called METs, or metabolic equivalents, where one MET is equal to 3.5 milliliters per kilogram per minute of oxygen uptake or utilization.

So I would say that the reason that VO2max has become such a popular way to do this is because it is a standardized test.

That doesn't mean it's always done correctly.

And we've got plenty of examples of how this can be done incorrectly, which is why for our patients, we actually do the test.

We got tired of relying on other labs to do it.

But for the most part, a well-trained technician can do this consistently.

And that makes it easy to study.

And that's why in the literature, you're going to see so much discussion where it comes down to METs or VO2 max.

The two can be used interchangeably.