Being active and breast cancer.

Does exercising reduce my breast cancer risk?

Yes, being active can reduce your risk of breast cancer by around 20%. It’s thought that exercise lowers the level of certain hormones and reduces inflammation. This can help lower the likelihood of breast cancer developing and progressing.

To reduce your risk, the World Health Organisation recommends at least 150 minutes of moderate, or 75 minutes of vigorous, physical activity weekly. It also recommends doing muscle-strengthening exercises at least twice a week. 

Key facts about exercise and breast cancer risk.

• Being active helps you maintain a healthy weight. This is especially important if you are a woman who has reached menopause or if you are male, as excess body fat increases breast cancer risk. 
• The largest risk reduction is seen in pre-menopausal women who do vigorous exercise. One large UK study found that very active women had a 23% lower risk of pre-menopausal breast cancer and a 17% lower risk of post-menopausal breast cancer.
• Even moderate activity makes a difference. A study found that as little as an hour of walking per week improved survival in women with breast cancer, with the greatest benefits found in women who walked for 3-5 hours per week.   
• Physical activity also reduces breast cancer risk in men and those with a family history or genetic predisposition to breast cancer, such as BRCA mutation carriers. 
• A study of women with a family history of breast cancer found that they had a 20% lower risk if they were physically active compared to inactive women at increased genetic risk.   

How does exercise reduce your breast cancer risk?

There are several ways that physical activity can reduce breast cancer risk, including:  

Reducing the levels of circulating sex hormones:  

High levels of sex hormones, especially oestrogen (and other proteins that help it function), are associated with an increased risk of breast cancer. 

Post-menopausal women who are overweight have higher levels of oestrogen. Following menopause, the main source of oestrogen becomes fat cells. Excessive fat can increase oestrogen levels, increasing breast cancer risk. Increasing the amount you exercise can help reduce the amount of body fat a person has.  

Changing the levels of hormones and growth factors that help your body break down and use food:  

Being active and having less body fat helps to control levels of metabolic hormones in your body, including insulin and the growth factor IGF-1 (small proteins that help cells grow). High levels of certain growth factors can cause cells to grow out of control, which may lead to cancer.

Staying active improves how your body uses insulin, which helps control blood sugar. This reduces the risk of insulin resistance, a condition that results in high blood sugar and high insulin levels. This condition is linked to a higher risk of breast cancer and other diseases like type 2 diabetes.

Reduces inflammation and improves your immunity: 

In both men and women, obesity, weight gain and being inactive lead to a persistent state of inflammation; this means that your immune system can be active when it shouldn’t be. Physical activity reduces inflammatory-causing factors in your body and increases anti-inflammatory factors.

Does exercise prevent breast cancer recurrence and increase survival?

Physical activity after a breast cancer diagnosis lowers the risk of recurrence by 20-30% and the mortality risk in diagnosed patients by 30-40%. 

One review that compared women diagnosed with breast cancer doing the least physical activity to those doing the most found that physically active women had a 40% lower risk of breast cancer mortality and a 42% lower risk of mortality from any cause. 

Start your prevention journey today.

Building exercise into your daily routine doesn't have to be hard. Here are four easy ways to get more active:

• Walk more. Take the stairs, park farther away, or get off the bus a stop early.
• Use chores as a workout. Do squats while you wait for water to boil or have a dance party while you clean.
• "Deskercise" at work. Stand up and stretch every hour, or do leg extensions and glute squeezes while you sit.
• Do mini-workouts at home. Use commercial breaks to do squats or jumping jacks, or follow a short workout video online. 
• Short on time - try “The Scientific 7 Minute Workout.” 

Remember, these small steps can make a big difference. Which one will you try first?

Further reading

For more information, read our Physical Activity and Breast Cancer science review.

Last review: Aug-23 | Next review: Aug-26.