Disclaimer: The information in this article is general in nature and is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your doctor or other qualified health professional before starting any exercise programme or with any questions you may have regarding a medical condition.
Researchers estimated that low physical activity was linked to 6,361 Australian cancer cases diagnosed in 2015. That was 4.8% of all cases that year. The figure comes from a modelling study, not a count of people whose cancers were proved to result from inactivity. It shows why activity matters for prevention at a population level, while no activity plan can remove an individual's cancer risk.
How was the estimate made?
The researchers combined Australian activity data from 2004–05, cancer diagnoses from 2015 and published estimates of how activity relates to cancer risk. They assumed a ten-year gap between the activity measure and the diagnoses. Their model covered 13 cancer sites, rather than the three considered in an earlier estimate.
Of the 6,361 estimated cases, 4,904 came from seven cancer sites where the evidence for activity was rated strong. The other six sites had weaker or more uncertain evidence. The model therefore gives an estimate under stated assumptions, not a direct observation of which person would have avoided cancer.
Did the number of inactivity-linked cancers triple?
An earlier Australian estimate counted 1,814 cases in 2010 across three cancer sites. This study examined 13 sites and used a different diagnosis year. The larger estimate is mainly a broader calculation; it does not show that an individual's risk tripled between 2010 and 2015. Comparing the two headlines without their methods would give the wrong impression.
What does the other number mean?
The study also modelled a modest shift in activity. If every Australian adult had moved up one of the study's activity categories in 2004–05, it estimated 2,564 fewer cancer cases in 2015. That is a comparison with an imagined population, not a promise that a short daily walk would prevent a set number of cancers.
Cancer Council identifies strong evidence for physical activity and lower risk of bowel, post-menopausal breast and endometrial cancers. Other cancer sites have different levels of evidence. The study's overall estimate should not be read as the same risk reduction for every cancer.
How can someone act on this?
Australia's current adult guidance recommends moderate or vigorous activity for at least 30 minutes on most days, strength activity twice a week, and less prolonged sitting. It also recommends several hours of light activity each day.
These recommendations describe different kinds of movement, which can fit into an ordinary week:
- Light movement: Break up long sitting periods with short walks or active tasks. This is worthwhile, but it is not the same intensity as a brisk walk.
- Moderate or vigorous activity: Try a brisk walk, class or game that suits your ability on most days. Build towards the current guidance rather than assuming the study tested one perfect dose.
- Strength work: Add suitable resistance activity on two days a week, as the adult guidance recommends.
When you want a session near home, KeepActive's group finder lets you compare activities and locations. Check the organiser's current details before attending. If you are living with cancer or receiving treatment, ask your care team about activity suited to your situation; this prevention study did not test cancer treatment.
