Most of the mortality benefit of exercise arrives below the 150-minute guideline

The World Health Organization recommends that adults do 150 to 300 minutes of moderate-intensity activity a week, or 75 to 150 minutes of vigorous-intensity activity, or an equivalent mix [s2]. The dose-response evidence underneath that number shows the largest differences in risk occurring below it — between doing nothing and reaching about half the recommendation — with progressively smaller and less certain differences as the dose rises above it [s1].

That is the point most often lost when the guideline is repeated. It is a target, not a threshold. Nothing in the evidence suggests that benefit switches on at 150 minutes.

What the guideline says

The 2020 WHO guidelines, published in full in the British Journal of Sports Medicine, cover children, adolescents, adults, older adults, and for the first time include specific recommendations for pregnant and postpartum women and for people living with chronic conditions or disability [s2]. For adults, the aerobic recommendation is 150–300 minutes of moderate-intensity or 75–150 minutes of vigorous-intensity activity per week, or a combination [s2]. For children and adolescents, an average of 60 minutes a day of moderate-to-vigorous activity across the week [s2]. Regular muscle-strengthening activity is recommended for all age groups [s2].

The guidelines also recommend reducing sedentary behaviour across all age groups — while stating explicitly that the evidence was insufficient to quantify a sedentary threshold [s2]. Their headline messages are that some physical activity is better than none, and that more is better for optimal outcomes [s2].

The curve behind the number

A 2023 dose-response meta-analysis assembled 196 articles covering 94 cohorts and more than 30 million participants [s1]. The evidence base was largest for all-cause mortality — 50 separate results, 163,415,543 person-years and 811,616 deaths — followed by cardiovascular disease incidence (37 results, 28,884,209 person-years, 74,757 events) and cancer incidence (31 results, 35,500,867 person-years, 185,870 events) [s1].

Activity was expressed in marginal MET-hours per week, where 8.75 mMET-hours corresponds to the recommended 150 minutes of moderate-to-vigorous activity [s1]. Differences in risk were greatest between 0 and 8.75 mMET-hours per week, with smaller marginal differences from there up to 17.5 mMET-hours per week — double the recommendation — beyond which additional differences were small and uncertain [s1].

At 8.75 mMET-hours per week, the relative risk was 0.69 (95% CI 0.65 to 0.73) for all-cause mortality and 0.71 (0.66 to 0.77) for cardiovascular mortality, with a weaker association for cancer mortality at 0.85 (0.81 to 0.89) [s1]. The authors estimated that if every insufficiently active person had reached 8.75 mMET-hours per week, 15.7% (13.1 to 18.2) of premature deaths would have been averted [s1].

The accelerometer data point the same way, more steeply

Self-reported activity is a poor measure, and the cohorts above mostly rely on it. A harmonised meta-analysis published in the BMJ in 2019 restricted itself to studies using accelerometers, pooling individual-level data from eight studies covering 36,383 participants of mean age 62.6, of whom 72.8% were women, with a median 5.8 years of follow-up and 2,149 deaths [s3].

Compared with the least active quarter, hazard ratios for death were 0.48 (95% CI 0.43 to 0.54) in the second quarter, 0.34 (0.26 to 0.45) in the third and 0.27 (0.23 to 0.32) in the most active [s3]. Crucially, intensity mattered less than the guideline language implies. For light physical activity alone the corresponding hazard ratios were 0.60, 0.44 and 0.38; for moderate-to-vigorous activity, 0.64, 0.55 and 0.52 [s3]. Any activity, regardless of intensity, was associated with lower mortality, in a non-linear dose-response [s3].

The same analysis found sedentary time associated with rising risk across quarters: hazard ratios of 1.28 (1.09 to 1.51), 1.71 (1.36 to 2.15) and 2.63 (1.94 to 3.56) compared with the least sedentary [s3].

The limits

All of this is observational. People who move more are different from people who move less in ways that adjustment cannot fully handle, and reverse causation is a genuine problem in this literature: early illness reduces activity before it is diagnosed, which inflates the apparent benefit of being active. The accelerometer analysis has a further limitation — a mean age of 62.6 and a mostly female sample [s3], which is not the general adult population.

The effect sizes should therefore be read as upper bounds on what a causal effect might be, not as estimates of one. What is more robust is the shape: steep at the bottom, flattening in the middle, uncertain at the top. That shape is consistent across self-report and device measurement, across outcomes, and across the two analyses described here.

For a reader, the practical implication of the shape is not that the guideline is wrong. It is that the distance between zero and something is where the evidence is strongest, and the distance between the guideline and twice the guideline is where it is weakest. The guidelines themselves say as much: some is better than none [s2].

This article is informational and is not medical advice. Anyone with a cardiovascular or musculoskeletal condition should discuss activity changes with a clinician.

Sources

• Non-occupational physical activity and risk of cardiovascular disease, cancer and mortality outcomes: a dose-response meta-analysis of large prospective studies — British Journal of Sports Medicine, 2023-02-28
• World Health Organization 2020 guidelines on physical activity and sedentary behaviour — British Journal of Sports Medicine, 2020-11-25
• Dose-response associations between accelerometry measured physical activity and sedentary time and all cause mortality: systematic review and harmonised meta-analysis — BMJ, 2019-08-21