Physical Activity and Cancer Prevention: What Research Suggests

The Evidence for Physical Activity

Research consistently indicates that regular physical activity is associated with a reduced risk of several cancer types. The World Cancer Research Fund (WCRF) identifies physical activity as having strong evidence for reducing the risk of colorectal cancer, breast cancer (post-menopausal), and endometrial cancer. Emerging research suggests it may also play a protective role in other cancers, including lung and liver cancer.

According to a major analysis published in JAMA Internal Medicine, which examined data from over 1.4 million participants, higher levels of leisure-time physical activity were associated with lower risks of 13 different cancer types. The risk reductions ranged from 10% to 42% depending on the cancer type.

The mechanisms by which physical activity may reduce cancer risk are multiple. Exercise helps regulate hormones such as oestrogen and insulin, reduces chronic inflammation, supports immune function, aids in maintaining a healthy weight, and improves gut transit time — all of which may influence cancer development.

How Much Activity Is Recommended

The HSE’s National Guidelines on Physical Activity for Ireland recommend that adults engage in at least 150 minutes of moderate-intensity activity per week, or 75 minutes of vigorous-intensity activity, or an equivalent combination of both. This aligns with recommendations from the WHO and the WCRF.

Moderate-intensity activities include brisk walking, cycling on flat ground, swimming, gardening, and dancing. During moderate activity, you should be able to talk but not sing. For cancer risk reduction specifically, the WCRF suggests that even activity beyond the minimum 150 minutes provides additional benefit — the more active you are, the greater the potential protection.

Vigorous-intensity activities include running, fast cycling, competitive sports, and aerobic classes. During vigorous activity, you would find it difficult to carry on a conversation.

The guidelines also recommend that adults minimise the time they spend being sedentary. Prolonged sitting has been independently associated with increased cancer risk, particularly colorectal and endometrial cancers, regardless of exercise levels. Breaking up long periods of sitting with short movement breaks — even standing and stretching — may help mitigate this risk.

Starting and Maintaining an Exercise Routine

The most effective exercise programme is one you can maintain consistently over time. For those who are currently inactive, the HSE recommends starting gradually and building up. Even small increases in activity provide health benefits. Walking is an excellent starting point — it requires no equipment, can be done almost anywhere in Ireland, and is suitable for most fitness levels.

Practical suggestions for increasing activity:

• Take a 30-minute brisk walk five days per week to meet the minimum recommendation
• Use stairs instead of lifts when practical
• Walk or cycle for short journeys rather than driving
• Join a local walking group, parkrun, or sports club — County Clare has numerous options along the Wild Atlantic Way and the Burren
• Set realistic goals and increase duration or intensity gradually over weeks
• Include variety to prevent boredom: combine walking with swimming, cycling, or a fitness class

For those who have been diagnosed with cancer or are undergoing treatment, physical activity during and after treatment may still be beneficial. Research suggests that exercise during cancer treatment can improve fatigue, mood, and quality of life. However, activity levels should be discussed with your oncology team and adapted to your individual circumstances.

The Role of Strength Training

The HSE guidelines also recommend muscle-strengthening activities on at least two days per week. These include bodyweight exercises, resistance band exercises, weight training, and activities such as yoga or Pilates that challenge muscular strength and endurance.

Strength training supports healthy body composition by maintaining lean muscle mass, which is metabolically active and helps regulate blood sugar and hormone levels. It is also particularly important for bone health, balance, and fall prevention as we age.

You do not need a gym membership to perform strength training. Bodyweight exercises such as squats, lunges, push-ups, and planks can be done at home. For those interested in practising at home, yoga equipment and accessories can provide helpful support for building a consistent routine.

Reducing Sedentary Behaviour

Beyond structured exercise, reducing the total amount of time spent sitting is increasingly recognised as important for health. Research published in The Lancet suggests that 60-75 minutes of moderate-intensity activity per day may be needed to offset the increased risk associated with sitting for 8 or more hours daily.

Practical steps to reduce sedentary time include using a standing desk or standing periodically during work, taking phone calls while walking, walking during lunch breaks, and setting reminders to move every 30-60 minutes during the working day.

Our guide on stress management explores additional lifestyle factors that complement physical activity in supporting overall health.

Key Takeaways

• Regular physical activity is associated with reduced risk of at least 13 cancer types, with strong evidence for colorectal, breast, and endometrial cancers
• The HSE recommends at least 150 minutes of moderate-intensity activity per week, with additional benefits from more activity
• Any increase in activity is beneficial — starting with walking and building up gradually is an effective approach
• Prolonged sitting is independently associated with increased cancer risk, even among people who exercise regularly
• Strength training on at least two days per week supports healthy body composition and overall health

Frequently Asked Questions

Can exercise reduce cancer risk if I am overweight?

Yes. Research indicates that physical activity provides cancer risk reduction benefits independent of weight status. While maintaining a healthy weight is itself protective, being active at any weight is better than being inactive. The combination of regular physical activity and a balanced diet is the most effective approach to both weight management and cancer risk reduction.

Is any type of exercise better than others for cancer prevention?

The evidence does not strongly favour one type of exercise over another for cancer prevention. Both aerobic activities (walking, swimming, cycling) and strength training appear to be beneficial. The most important factor is regularity and consistency. Choose activities you enjoy and can sustain long-term.

Should I exercise if I am currently receiving cancer treatment?

Research increasingly supports the benefits of physical activity during cancer treatment, including reduced fatigue and improved quality of life. However, the type and intensity of activity should be tailored to your individual situation. Always discuss exercise plans with your oncology team before starting or modifying an exercise programme during treatment.