Sitting for more than 30 minutes at a time is linked to a higher risk of dying from cancer, while breaking up long sitting spells with light activity appeared to lower that risk, according to new data . But media reports of the study left many questions unanswered. Here's what you need to know.
What did this study actually find?
The main message is simple: it's not just how long you sit each day, but how you sit that seems to matter. People who stayed seated for long, uninterrupted stretches - 30 minutes or more at a time - had a higher risk of dying from cancer. By contrast, those who got up regularly, even just to stand or walk briefly, appeared to have a lower risk. In other words, two people might sit for the same total number of hours in a day, but the one who breaks it up more often may be better off.
Does this mean sitting causes cancer?
No, this study does not show that sitting causes cancer. It shows a link between long periods of uninterrupted sitting and a higher risk of dying from cancer, but that is not the same as proving one causes the other.
Studies like this observe people's habits and what happens to them over time, but they cannot fully account for every difference between individuals. Other factors - such as general health, diet or lifestyle - could also play a role in explaining the findings.
Could it be the other way round?
Yes, that's a real possibility. People who are already becoming unwell - even before they are diagnosed - may naturally start to sit more because they feel tired or less able to move around.
The researchers were aware of this and tried to reduce its impact. They excluded the first two years of data on the assumption that cancers diagnosed soon after the study began may already have been developing and influencing people's activity levels. That helps make the findings more reliable, but it doesn't completely rule out this explanation.
If I already exercise a few times a week, isn't that enough? And does getting up briefly really help?
Regular exercise is still very important, and nothing in this study changes that. But it highlights something slightly different: you can be active in short bursts - for example, going for a run or to the gym - and still spend long stretches of the rest of your day sitting.
This study suggests those long, unbroken periods of sitting may carry their own risks. The encouraging part is that the change needed is small. Getting up every 20 to 30 minutes and moving around briefly - even for a minute or two - may be enough to make a difference. It's less about doing more intense exercise and more about avoiding being still for too long.
The study says risk could be up to 20% lower - is that a big deal?
That figure can sound dramatic, but it needs a bit of context. It refers to a relative difference rather than the overall, real-world risk. For instance, if the chance of dying from cancer over a certain time period is about five in 100 people, a 20% reduction would lower that to around four in 100. So while the percentage sounds large, the actual change for any one person is relatively modest.
That said, when you look at whole populations, even small shifts like this can still add up to a meaningful impact overall.
Who was studied, and does it apply to everyone?
The study used data from the UK Biobank , a large and very useful research resource. However, the people who take part tend to be somewhat healthier and more affluent than the general population. That means the results may not apply equally to everyone.
Younger people, for example, generally have a much lower risk of cancer to begin with. People with disabilities or long-term illnesses may not be able to move around as easily. And those in physically active jobs are unlikely to be affected in the same way. Even so, the overall message - that long periods of inactivity are probably not ideal - is likely to be broadly relevant.
What were the study's main limitations?
This is a well-conducted study, but it has some important limits, as do all studies. It cannot prove cause and effect, only an association.
There may be other differences between people who sit more and those who sit less that help explain the results. The measurements of activity were taken over a relatively short period, which may not reflect people's long-term habits.
The study also looks at cancer deaths overall, rather than specific types of cancer, which may behave very differently.
Finally, although the researchers tried to account for people who were already becoming unwell, this cannot be completely ruled out. Taken together, the findings are suggestive rather than definitive. However, this study is in keeping with others on the same subject that show similar findings.
What's the one practical thing to do?
The main message is: try not to sit for long, unbroken stretches. A good rule of thumb is to stand up and move around for a minute or two every 20 to 30 minutes. That could be as simple as walking to make a drink, taking a short break from your desk, or standing during a phone call. It's an easy habit to build, and there's little downside to it.
Importantly, this isn't about replacing regular exercise or making drastic changes to your routine. It's about adding small, frequent moments of movement into the day. Over time, these small interruptions to sitting may help support overall health. The evidence is still evolving, but this is a practical, low-effort step that fits well with broader advice to stay active and avoid sitting for long periods.
Justin Stebbing does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
