Encyclopedia entry

VO2 max

VO2 max is the maximum rate at which the body can consume oxygen during exhaustive exercise, measured in millilitres of oxygen per kilogram of body weight per minute (ml/kg/min). It is the single best predictor of all-cause mortality after adjusting for other cardiovascular risk factors. The headline number on every UK longevity clinic baseline assessment.

How VO2 max is measured

• Gold standard (metabolic cart): ramped exercise on a treadmill or bike with a mouthpiece measuring expired air. Genuine VO2 max requires reaching volitional exhaustion at a respiratory exchange ratio greater than 1.10.
• Submaximal estimate: Cooper test, Rockport walk test, or smartwatch estimate. Useful but approximate.
• Lab-grade clinics: Hooke, Echelon Health, Reliant Healthcare and similar UK longevity providers offer metabolic-cart testing as standard.

Typical values

Sedentary adult: 25 to 35 ml/kg/min. Recreationally active: 35 to 45 ml/kg/min. Athletic: 45 to 60 ml/kg/min. Elite endurance: 60 to 80+ ml/kg/min. Values decline approximately 10 percent per decade after age 30 unless actively trained. Age-adjusted percentiles are the most useful comparison for individuals.

Why VO2 max is the headline mortality predictor

Multiple cohort studies (most notably the 2018 JAMA Network Open analysis of 122,007 patients) show VO2 max predicts all-cause mortality with hazard ratios stronger than smoking, hypertension, or type 2 diabetes. Moving from the lowest 25 percent percentile to the second-lowest 25 percent is associated with a 50 percent reduction in mortality risk; the move from second-lowest to highest is a further 50 percent reduction. The marginal value of fitness improvement is highest at the low end.

What GLP-1 weight loss does to VO2 max

VO2 max is expressed per kilogram of body weight. Weight loss alone improves the value mechanically (same oxygen consumption, lower denominator). The absolute oxygen-uptake capacity (ml/min) does not automatically improve and may decline with lean-mass loss if no training is added. The combination of GLP-1 plus structured cardiovascular training is the protocol that improves both relative and absolute VO2 max.

Related: DXA · muscle preservation · longevity hub.