How Much Exercise Is Enough?
Somebody told you 150 minutes a week. Maybe it was a poster in a doctor’s surgery, maybe an app. It is the most repeated number in fitness, and if you are starting from nothing it lands as a verdict rather than a target. Two and a half hours. Every week. Forever.
The honest answer is more interesting than the number, and more useful. It has three parts: the floor is far lower than you think, the ceiling is far higher than the guideline implies, and almost nobody tells you both at once.
The floor is lower than you have been told
A prospective study pooled the Norwegian HUNT and Tromsø cohorts and followed 87,340 adults for a median of 13.5 years. Participants were sorted by how much they moved, and the lowest active tier was defined generously. It explicitly included taking it easy without breaking into a sweat.
Against people who did nothing at all, that lowest tier was associated with 9% lower stroke risk and 11% lower mortality (Journal of the American Heart Association, doi 10.1161/JAHA.126.048812, August 2026). Moderate activity reached 19% and 18%. High activity reached 18% and 22%, which is to say the top tier did not beat the middle one on stroke.
This is observational, so it shows association rather than cause, and activity was self-reported, which people overstate. But the shape holds across a very large sample followed for a long time, and the shape is the point. The largest single step in that data is the one from nothing to something.
A second study makes the same case from a different angle. A two-cohort analysis combining the China Kadoorie Biobank and UK Biobank, 330,178 older adults in total, modelled what happens when sitting time is swapped for movement. Replacing 30 minutes a day of sitting with activity was associated with lower mortality at every intensity (Journal of Epidemiology and Community Health, doi 10.1136/jech-2025-225695, August 2026). In the Chinese cohort the benefit was comparable whether the movement was light or vigorous.
That framing is worth stealing for your own head. The guideline framing says you are failing until you reach 150 minutes. The substitution framing says the next half hour you spend not sitting is the win.
The ceiling is higher than the guideline implies
Here is the part most fitness writing leaves out, and leaving it out is how the category loses trust.
A UK Biobank analysis measured activity by device rather than by memory. Over 100,000 people wore wrist accelerometers, and the 17,088 who also took a cycle fitness test and started out with no heart disease were followed for 7.8 years. Meeting the 150-minute guideline was associated with an 8 to 9% reduction in cardiovascular risk. Getting past a 30% reduction took 560 to 610 minutes a week, roughly nine to ten hours. Only 12% of that group got there (British Journal of Sports Medicine, doi 10.1136/bjsports-2025-111351).
Two caveats belong with that number rather than in the small print. Of the 1,233 cardiovascular events recorded, 874 were atrial fibrillation, so the dose-response curve is mostly a statement about one condition rather than about heart attacks and strokes generally. And the study is observational.
Still, the direction is uncomfortable and worth sitting with. If your goal is maximal cardiovascular protection, 150 minutes is a starting line rather than a finish.
One more detail from the same paper is worth knowing, and it cuts both ways. Fitness barely changed the dose: the least fit needed about 370 minutes a week for a 20% reduction, the fittest about 340. That gap is smaller than most people expect. What it does not mean is that half an hour of extra walking closes the distance, because each fitness group was only ever compared with the inactive people at its own level. The least fit group was not an untrained beginner either. Fitness came from a short bike test, odd readings were dropped, and the authors think their volunteers were healthier and fitter than most people, so if you are frail or badly out of shape, treat these numbers as somebody else’s.
How to hold both numbers at once
Both things are true, and they are answers to different questions. Small amounts of movement are associated with real benefit, and where cardiovascular risk is the outcome, large amounts are associated with more. Stroke was the one place the Norwegian data stopped improving past the middle tier, so where the curve flattens depends on what you are measuring. The mistake is letting the second fact make the first one feel pointless.
Three things follow that you can use.
Compare against zero, not against ideal. On a week that has collapsed, the comparison that matters is a short walk versus the sofa, not a short walk versus the session you planned. The 330,178-person substitution analysis is the version of that with data behind it.
Stop treating the guideline as a pass mark. It is a public health average built for populations. You are one person with a specific week. What you can repeat beats what you can achieve once.
Pick the constraint you have. Work out which thing is actually stopping you, rather than assuming you just need to try harder. Not enough time, not enough energy, and not knowing what to do with the twenty minutes you have are three different obstacles, and each one needs a different fix. The no time, no energy, no motivation piece takes them one at a time.
What the rest of this series covers
The dose question splits into pieces, and each has its own evidence.
- The smallest amount that still shows up in the data: the minimum effective dose.
- Whether it matters how you split the week: one long session or three short ones.
- How much strength work, specifically: how much strength training a week is enough.
- Whether lifting and cardio need their own days: doing both in one session.
- How hard any of it needs to feel: the case for the middle setting.
- How long a stretch has to be to change anything: how long to hold a stretch.
None of them will give you a number that fits everybody. The useful version of this question was never “what is the correct dose”. It is “what is the smallest thing I will still be doing in six months”.
ZeroFit is built for the version of that question you have on a bad week. Two questions, one session, no plan to design. Get beta access.
ZeroFit content is educational and not medical advice. If you have an injury, a health condition, or you’re pregnant, check with a qualified professional before starting any new movement routine.