Why VO₂ Max Matters More Than Your Weight

If someone asked you to name the single most important number for your health, chances are you’d think of your weight.

Or perhaps your BMI.

Maybe your body fat percentage. Although the chances of measuring this accurately at home are slim. 

For decades, we’ve been taught that these figures define our health, fitness and even our longevity. We celebrate weight loss, obsess over the number on the scales and quietly judge ourselves if it creeps up after a holiday.

But what if we’ve been focusing on the wrong metric?

Increasingly, researchers believe there’s another number that tells us far more about how healthy (and how long) we’re likely to live.

And that’s VO₂ max.

And unless you’re a runner, cyclist or HYROX enthusiast, there’s a good chance you’ve never paid much attention to it.

So, What Is VO₂ Max?

Put simply, VO₂ max measures how efficiently your body uses oxygen during exercise.

It’s the maximum amount of oxygen your body can take in, transport and use while you’re working at your hardest.

That might sound like something reserved for elite athletes wearing masks in sports science labs, but it’s actually one of the clearest indicators of your cardiovascular fitness.

Think of your body like a car.

Your muscles are the engine, but oxygen is the fuel that keeps everything running. The more efficiently your heart, lungs and muscles can deliver and use oxygen, the better your engine performs.

And unlike your weight, VO₂ max tells us something about what your body can do.

Cardiorespiratory fitness is consistently associated with a lower risk of heart disease, stroke, type 2 diabetes and premature death.

In fact, some researchers have argued that low cardiorespiratory fitness may be as significant a health risk as smoking, high blood pressure or diabetes.

That’s because VO₂ max reflects the health of multiple systems at once.

Your heart has to pump efficiently. Your lungs have to deliver oxygen effectively. Your blood has to transport it. Your muscles have to use it.

If any part of that chain isn’t working well, your VO₂ max tends to suffer.

Two people can weigh exactly the same and have dramatically different levels of fitness.

Equally, two people with the same BMI can have very different risks of developing chronic disease.

Someone who exercises regularly, has good cardiovascular fitness and a high VO₂ max often has better long-term health outcomes than someone who is lighter but physically inactive.

That’s not to say weight is irrelevant.

Carrying excess body fat can increase the risk of a range of health conditions.

But weight alone doesn’t tell you how healthy your heart is, how strong your lungs are or how efficiently your body functions.

We’re going to hit you with some bad news here. But stick with it - there’s good news after. So. Like muscle mass and bone density, VO₂ max gradually declines as we get older. The good news? Much of that decline isn’t inevitable.

Regular aerobic exercise can slow it significantly.

Research suggests that people who remain physically active throughout adulthood maintain substantially higher cardiorespiratory fitness than those who become sedentary.

In other words, while ageing is unavoidable, becoming dramatically less fit isn’t.

Can You Improve Your VO₂ Max?

Absolutely. And you don’t need to become a marathon runner to do it.

The biggest improvements tend to come from combining different types of training.

Steady Zone 2 cardio builds the aerobic base that allows your body to use oxygen more efficiently over longer periods.

Higher-intensity interval training challenges your cardiovascular system closer to its limits, encouraging further adaptations in your heart and muscles.

Strength training plays an important supporting role too, improving movement efficiency and helping you maintain the muscle needed to stay active as you age.

Perhaps most importantly, consistency beats intensity. An occasional all-out workout won’t transform your fitness, but months of regular movement will.

How to measure VO₂ max

Many modern fitness watches estimate VO₂ max based on your heart rate and exercise data.

They’re not as accurate as laboratory testing, but they can still be useful for tracking trends over time. So, rather than obsessing over the exact figure, think of it as another measure of progress.

If your VO₂ max is improving, your cardiovascular fitness is probably improving too.

We’ve spent years treating body weight as the ultimate marker of health. But your weight can’t tell you how strong your heart is. Or how efficiently your lungs deliver oxygen.

It can’t tell you whether you’ll be able to chase your grandchildren around the park, hike into your seventies or recover quickly after climbing a flight of stairs.

VO₂ max can.