Step into most doctors’ offices, and the scale is usually your first stop. Body mass index (BMI) — an estimate of your body-fat percentage based on weight and height — is used by many healthcare providers to gauge your health risks, even though it’s been critiqued as a shortsighted measure of overall health. (See “Beyond BMI: Why True Health Is About More Than What You Weigh” for more.)
A better marker of health is cardiorespiratory fitness, according to a 2024 British Journal of Sports Medicine meta-analysis.
The investigation involved 20 studies conducted since 1980. Combined, they include data on 398,716 people. Compared with previous research, the results came from a greater proportion of women (33 percent) and a more globally diverse sample.
“The takeaway message of our study is that, from a health perspective, the risks of being unfit are far worse than the risks associated with carrying extra weight,” says corresponding author and physiologist Siddhartha Angadi, PhD, a University of Virginia associate professor of kinesiology.
Healthcare’s reliance on BMI is representative of a public health strategy that is largely focused on weight loss, the review authors state.
Cardiorespiratory fitness, on the other hand, is the capacity of the cardiovascular and respiratory systems to supply oxygen to the muscles during exercise. When you work out, your heart beats faster to deliver the oxygen from your lungs to your muscles, explains Samantha McKinney, RD, who helps lead nutrition and LTH supplement education at Life Time. Your muscles use that oxygen to generate energy in the form of adenosine triphosphate, or ATP. This energy production is a sign of aerobic fitness and the ability to handle more activity and stress.
Cardiorespiratory fitness is measured by your VO2 max —
the maximum volume of oxygen that your body can use at any one time.
Cardiorespiratory fitness is measured by your VO2 max — the maximum volume of oxygen that your body can use at any one time. Though there are ways to estimate it, measuring VO2 max requires a more complex test than simply stepping onto a scale, which Angadi says is a key reason “BMI persists as the primary health indicator.”
Most notably, the meta-analysis found that cardiorespiratory fitness yielded significant benefits for participants’ health regardless of their BMI.
“Unfit individuals, whether they’re considered normal weight, overweight, or obese, had a two- to threefold greater risk of mortality compared to fit individuals across weight categories,” Angadi explains. “Importantly, once fitness status was accounted for, there were no increases in the risk of death in overweight and obese individuals.”
(For more on assessing your cardiorespiratory fitness and VO2 max, see “How to Increase Your VO2 Score.”)
This article originally appeared as “Rethinking Health Metrics” in the July/August 2025 issue of Experience Life.
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