Even regular exercise can't beat the damage done by this common daily habit that increases cancer risk, scientists warn

Modern lifestyles have made sitting a normal part of the day, whether it's while working at a desk, driving, watching television or scrolling on a phone. Although regular exercise is one of the best ways to stay healthy, experts have increasingly warned that long hours of uninterrupted sitting can still take a toll on the body. Now, a new study suggests that this everyday habit may even be linked to a higher risk of developing and dying from certain cancers, showing that staying active does not completely cancel out the effects of prolonged sitting.

The findings come from researchers at the University of Glasgow and were published in the journal PLOS Medicine. The study looked at how spending long stretches of time sitting without breaks may affect cancer risk over the long term.

Long periods of sitting were linked to higher cancer risk

For the study, researchers analysed data from 91,292 adults enrolled in the UK Biobank. Participants, aged between 37 and 73, had no previous history of cancer and wore wrist activity monitors continuously for seven days so researchers could accurately measure their daily movement and sedentary time.


Instead of looking only at the total amount of time people spent sitting, the team also examined how that time was accumulated. They defined prolonged sedentary behaviour as sitting for at least 30 minutes with almost no movement, while interrupted sedentary behaviour referred to sitting that was regularly broken up by physical activity.

The participants were followed for around 12 years, during which researchers tracked the development of several cancers, including breast, colorectal, pancreatic, kidney, liver and thyroid cancers.

The analysis found that every additional hour of prolonged sitting was associated with a 3% higher risk of developing cancer and a 9% higher risk of dying from cancer. Obesity-related cancers, including pancreatic and colorectal cancer, showed an even greater increase, with risk rising by around 5% for every extra hour of prolonged sitting.

Why breaking up sitting time matters

Researchers believe long periods of inactivity may contribute to chronic inflammation in the body, creating conditions that can damage DNA and increase the likelihood of cancer-related changes in cells. Prolonged sitting has also been linked to insulin resistance, which is associated with type 2 diabetes and has previously been connected to tumour growth.

However, the researchers emphasised that the study found an association, not proof that sitting directly causes cancer.

The study also highlighted that even small changes in daily habits could make a difference. Replacing 30 minutes of prolonged sitting with light activity, such as walking, was associated with an 18% lower risk of dying from cancer. Swapping that time for moderate activity, including brisk walking or cycling, was linked to an 8% reduction in cancer death risk. Meanwhile, replacing just five minutes of prolonged sitting with vigorous exercise, such as running or swimming, was associated with a lower overall cancer risk.

Movement throughout the day should not be ignored

The study authors said, "Our findings suggest that the health effects of sedentary behaviour may depend not only on total sedentary time, but also on whether that time is accumulated in prolonged bouts or interrupted by activity."

Lead author Dr. Frederick Ho of the University of Glasgow said, “What our data shows is that sitting for more than 30 minutes at a time is particularly linked to a higher risk of cancer. The good news is that breaking up your sitting time with something as simple as a short walk could be protective.”

He added, “Current health guidelines focus heavily on moderate or vigorous exercise, but our findings show that light movement should not be ignored. Moving forward, clinical trials will help us move beyond blanket advice and develop personalised strategies for breaking up sitting time.”

Experts who reviewed the findings also cautioned against interpreting the results as evidence that sitting itself directly causes cancer. Instead, they said the research reinforces an important health message: meeting daily exercise goals is beneficial, but regularly getting up and moving throughout the day may also play an important role in lowering long-term health risks.