Each step up in fitness is linked to about 13 percent lower risk of dying

A cardiorespiratory fitness test can predict how long someone is likely to live better than several of the risk factors doctors already track. Each single-MET improvement in that fitness level — roughly the aerobic gain from moving from an easy walk to a brisk one — has been linked to about a 13% lower risk of dying from any cause.

That figure comes from research spanning more than four million observations across dozens of cohorts, produced by different research teams working from different data more than a decade apart, with strikingly similar results each time.

A Single Number From Two Decades of Data

The 13% figure traces to a 2009 meta-analysis in JAMA led by Satoshi Kodama, which pooled studies of healthy men and women and calculated that all-cause mortality and cardiovascular disease risk decreased 13% and 15%, respectively, per 1-MET increase in cardiorespiratory fitness. A MET, short for metabolic equivalent of task, measures oxygen consumption relative to sitting quietly; one MET equals 3.5 millilitres of oxygen per kilogram of body weight per minute, and a 1-MET gain is roughly the aerobic improvement many adults can achieve through a few months of regular aerobic exercise.

The same body of research found the pattern was not limited to otherwise healthy adults. In a larger group of patients undergoing cardiac rehabilitation, each 1-MET gain corresponded to a 13% mortality reduction among those who started with high baseline fitness, above roughly 8 METs, and a 30% reduction among those who started with low baseline fitness, below roughly 5 METs — meaning the same unit of improvement mattered most for the people who had the least fitness to begin with.

Confirmed Again With 3.8 Million More Observations

Fifteen years later, a far larger analysis reached nearly the same conclusion. A 2024 systematic review and meta-analysis led by Ben Singh, of the Alliance for Research in Exercise, Nutrition and Activity at the University of South Australia, pooled 42 studies representing 35 cohorts and 3,813,484 observations and found that each 1-MET increase in fitness was tied to a 14% lower risk of all-cause mortality and a 16% lower risk of cardiovascular death.

The analysis covered 362,771 all-cause deaths and 56,471 cardiovascular deaths across the pooled cohorts, and the association held regardless of whether fitness was measured directly through a maximal treadmill test, estimated from a shorter submaximal exercise test, or calculated from a non-exercise algorithm using age, sex and other factors. Singh’s team said that consistency matters practically, since it means fitness screening does not require the specialized lab equipment a maximal treadmill test demands to still produce a useful, comparable estimate.

Why Doctors Call Fitness a Vital Sign

The consistency across two generations of research is part of why the American Heart Association, in a 2016 scientific statement led by Robert Ross, argued that cardiorespiratory fitness should be assessed in clinical practice alongside vital signs like blood pressure and heart rate. The statement, co-authored by cardiovascular researcher Ross Arena, concluded that low fitness carries a higher risk of cardiovascular disease, all-cause mortality and several cancers, and can be a stronger predictor of death than smoking, high blood pressure or elevated cholesterol.

Arena has separately argued for framing “movement as a vital sign” even more broadly, proposing that clinicians ask patients about daily step counts and sedentary time alongside structured exercise, on the reasoning that each 1-MET improvement, particularly in the 5-to-10-MET range where most adults fall, delivers something in the range of a 10% to 30% reduction in premature mortality risk depending on where someone starts.

Fitness is not the only movement measure tied to mortality in this line of research. The same editorial that reported Kodama’s figures also points to adjacent metrics: each additional 1,000 daily steps has separately been linked to a 6% reduction in all-cause mortality, while sitting more than 10 hours a day has been linked to a 65% higher risk of death from any cause compared with sitting fewer than 4 hours. Cardiorespiratory fitness carries the strongest and most consistent association of the group, but the pattern suggests fitness is one part of a broader movement picture rather than the only number worth tracking.

Turning a MET Into a Realistic Workout Plan

None of the research implies that only elite fitness levels matter. The Centers for Disease Control and Prevention recommends that adults get at least 150 minutes of moderate-intensity aerobic activity, or 75 minutes of vigorous activity, spread across the week — a target well within reach of the modest fitness gains the mortality studies describe, rather than the extreme training regimens elite endurance athletes pursue.

Any activity that sustains an elevated heart rate for an extended stretch — brisk walking, cycling, swimming or running — raises cardiorespiratory fitness over weeks of consistent practice, which is part of why the CDC frames its guidance in minutes of activity rather than in METs directly. The two measures move together, but a MET value still requires an exercise test, maximal or estimated, to quantify in an individual rather than assumed from activity minutes alone.

The relationship in both the 2009 and 2024 analyses is observational: cohort studies can show that higher fitness tracks with lower mortality across large populations, not that raising any one individual’s fitness by exactly one MET will extend that person’s life by a fixed amount. Even so, Kodama’s team and Singh’s team, working a decade and a half and an ocean apart from almost entirely different data, arrived at nearly the same number — an unusual level of agreement in population health research, and part of why cardiorespiratory fitness keeps being described as a vital sign rather than just another statistic.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

More from Morning Overview