A new study funded by World Cancer Research Fund has found that activity throughout the day, with peaks in the morning and late afternoon, correlated with an 11% reduced risk of developing colorectal (also known as bowel) cancer, compared with other patterns of exercise studied.
This study used accelerometer data (which measures movement) to analyse daily activity. It used a statistical method that examines all of the data and finds common patterns, and how those patterns might be related to the risk of colorectal cancer.
Researchers from Regensburg University utilised data from the UK Biobank, which had contacted 86,252 randomly selected individuals (56% of them women), asking them to wear accelerometers to track their movement over 1 week and following them for 5 years to monitor the development of colorectal cancer. When studying the data, researchers identified a 2-peak pattern of daily physical activity associated with reduced colorectal cancer risk.
The researchers identified 4 different patterns of physical activity throughout the day:
- Continuous day-long activity
- Activity later in the day
- Early and late-day activity
- Activity in the middle of the day and during the night
The 3rd pattern, where people were active both in the early and late parts of the day, was associated with an 11% lower risk of colorectal cancer, compared with 6% for day-long activity and no change for middle of the day and the night. Data from activity later in the day only was inconclusive. These findings held true even when considering factors such as smoking, shift work and other variables that could affect a person’s cancer risk.
Impact on sedentary lifestyles
In addition, the researchers found that a day-long activity pattern most effectively reduced colorectal cancer risk among individuals who were more sedentary. This may be because the effect of physical activity becomes more obvious when contrasted with a previously more inactive lifestyle, meaning that those who are fit and healthy are already at a reduced level of cancer risk. These findings show how beneficial physical activity can be, especially in those who are more sedentary.
Dr Helen Croker, Assistant Director of Research and Policy at World Cancer Research Fund, said:
“Being physically active is one of our Cancer Prevention Recommendations, and we know that this cuts cancer risk. These intriguing new findings offer potential for developing more specific recommendations, including patterns and timing of physical activity, for reducing cancer risk. This shows the vital importance of World Cancer Research Fund continuing to support research that expands our knowledge to inform cancer prevention going forwards.”
Prof Michael Leitzmann, Chair of the Department of Epidemiology and Preventive Medicine at the University of Regensburg, Germany, who was the lead investigator in the study, said:
“Our study highlights that not only is physical activity important for reducing colorectal cancer risk, but the timing of peak activity throughout the day could play a crucial role. By identifying specific times – early morning and late day – when physical activity is most beneficial, our findings open new avenues for targeted prevention strategies. If confirmed by future research, this could provide a simple yet impactful way for individuals to further reduce their cancer risk through the timing of their exercise.”
Read the paper
Stein, M.J., Baurecht, H., Bohmann, P. et al. Diurnal timing of physical activity and risk of colorectal cancer in the UK Biobank. BMC Med 22, 399 (2024).
About the UK Biobank
The UK Biobank is a large, population-based prospective study, established to allow detailed investigations of the genetic and non-genetic determinants of the diseases of middle and old age. It has 500,000 UK participants between the ages of 40–69.
About the University of Regensburg
The University of Regensburg is a nationally and internationally renowned comprehensive university with an excellent research spectrum, an attractive range of courses and a high sense of social responsibility. The UR stands for diversity, openness to the world and shaping the future. Its research strength is demonstrated by 6 Collaborative Research Centers funded by the German Research Foundation (DFG) and 9 grants from the European Research Council.
In 2017, the Institute for East and Southeast European Studies (IOS), an affiliated institute of the UR, was the first institution in Regensburg to be accepted into the renowned Leibniz Association, followed in 2022 by the Leibniz Institute for Immunotherapy, which emerged from the Regensburg Center for Interventional Immunology. In May 2024, the Regensburg Center for Ultrafast Nanoscopy opened at the university, where the ultra-fast quantum movements of atoms and molecules are researched using innovative, high-resolution slow-motion cameras. In spring 2022, the Science Council recommended funding for the Center for Immunomedicine in Transplantation and Oncology at the UR, a center for basic research in immunomedicine.
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Breast cancer is now the most common cancer in the world. We asked our researcher to explain how physical activity plays a key role in reducing breast cancer risk.
Evidence suggests that inactivity and sitting down too much increase a woman’s risk of breast cancer, and that exercise after a breast cancer diagnosis lowers a woman’s risk of dying from cancer. How close are we to knowing how strong these links are?
Brigid Lynch: I think we are now at a point where we can say that physical inactivity causes breast cancer. The evidence is consistent and robust, and we can triangulate evidence from:
- observational studies
- Mendelian randomisation [a research method that uses genetic variants associated with risk factors of interest to examine causal effects]
- systematic reviews [a structured analysis of all the literature on a particular topic]
The evidence isn’t as clear for sedentary behaviour, as there are far fewer studies on this topic.
There is also less robust evidence for exercise after a breast cancer diagnosis. The research on this topic comes from observational studies, which are subject to considerable selection bias [arising from errors in choosing the individuals or groups to take part in a study], measurement error, and reverse causation [attributing a cause from a consequence]. So we need additional, carefully-designed studies on these latter two topics.
> More on physical activity and breast cancer survivors
What’s going on in a woman’s body when she does or doesn’t exercise? It may seem strange that exercise, which we assume is to do with muscle/bone/respiratory/cardiological health, can have such an impact on a small group of cells in a woman’s breast.
BL: We recently concluded a study funded by Wereld Kanker Onderzoek Fonds [the Dutch part of the World Cancer Research Fund International network]. In this project we systematically reviewed and meta-analysed the mechanistic [biological] evidence linking physical inactivity to breast cancer risk, focusing on 3 potential biological pathways:
- sex steroid hormones
- insulin/insulin-like growth factor (IGF) signalling [IGF is a protein that can promote cell division and inhibit cell death, which can lead to tumour development]
- inflammation
We found clear evidence that sex steroid hormones increase the risk of breast cancer, and that physical activity reduces the circulating levels of sex steroid hormones.
Although physical activity had an effect on insulin/IGF signalling and inflammation, there was minimal evidence that these pathways played a role in breast cancer risk. We weren’t able to rule out insulin/IGF signalling and inflammation as being important because there were not many high-quality, low risk of bias studies on these topics.
In summary, there is a clear biological pathway from physical activity to reduced breast cancer risk via sex hormones, particularly oestrogens and androgens. And as physical activity is important for so much more than cancer prevention, it’s critical to build this into your everyday routine!
When we talk about physical activity, are we talking about running and going to the gym? Or is it simply sitting down less?
BL: The studies that have focused on physical activity are nearly all talking about moderate to vigorous intensity activity, so this means activities that raise your heart rate and make it harder to talk while exercising. Moderate physical activity could be a brisk walk or a bike ride to the shops; vigorous physical activity uses higher levels of energy and includes running, fast swimming and aerobics.
We know that many girls exercise less in their teenage years. In light of your research on the connections between breast cancer and activity, how concerning is this?
BL: We know that people who maintain their exercise levels through childhood and adolescence into adulthood are more likely to remain active. It’s concerning that so many girls reduce their physical activity during teenage years, but there are many good programmes that are aimed to help reverse this trend.
After speaking to Prof Lynch, we asked Dr Ioana Vlad from World Cancer Research Fund International’s Policy and Public Affairs team to share examples of countries encouraging women and girls to exercise more.
- Every Body Active is a lottery-funded programme in Northern Ireland that aims to increase participation in sport among traditionally underrepresented groups, including women and girls aged 14–25.
- Universo Mujer II is a project in Spain that aims to promote and increase female participation in all areas of sport.
- Tuttingoal is a scheme by the Italian Football Federation, in collaboration with the Ministry of Education, University and Research, to encourage participation in football by school-age children, with children setting themselves up as sports clubs and building teams of 5 boys and 5 girls.
- Terre de Jeux 2024 aims put more sport in the daily life of inhabitants in France and its oversea territories.
These examples are from our MOVING database of global policies designed to promote physical activity.
