World Cancer Research Fund regularly reviews all the latest evidence on certain risk factors and cancers as part of our Global Cancer Update Programme.
In autumn 2022, we published our review of evidence on how a woman’s risk of dying after a breast cancer diagnosis is affected by her weight, diet and physical activity.
Many people living with and beyond a cancer diagnosis are interested in the latest research, so we’re sharing the results here. However, the evidence we found, although important, was limited. Evidence can be limited in many ways, such as:
We have complete confidence in the rigour of our review of breast cancer mortality studies, but since the evidence we found was limited, we weren’t able to make formal recommendations. However, it’s likely that following the healthy living guidelines coming out of this work will benefit women after a breast cancer diagnosis.
Where we do have advice from our collaboration with the NIHR Cancer and Nutrition Collaboration and the BDA Oncology Specialist Group, we link to that advice.
If you have any questions about this research, please email firstname.lastname@example.org and we’ll be happy to help.
We commissioned a systematic review – examining all the published research on a particular subject – of studies up to 31 October 2021.
The review found some limited evidence that eating food that contains soy reduced a woman’s risk of death and the risk of breast cancer recurring.
The studies measured the amount of soy in women’s diets then estimated the amount of isoflavones and/or soy protein, using questionnaires given to patients. The studies didn’t distinguish between different soy food; the focus was on the overall amount in the diet.
The review also found some limited evidence that dietary fibre reduced a woman’s risk of death.
The review also found some limited evidence that women with healthy eating patterns had a reduced risk of death. In these studies, the eating patterns were low in fat and high in fibre, fruit and vegetables, and followed World Cancer Research Fund’s Cancer Prevention Recommendations.
The review found some limited evidence that doing more physical activity lowered a woman’s risk of death and the risk of breast cancer recurring.
The studies reviewed wasn’t able to didn’t look in detail at how much physical activity women with breast cancer should do – we need more evidence on what type and amount of activity, such as frequency, duration and intensity. In the absence of these details, women living with and beyond breast cancer should aim to follow national guidelines for physical activity, under the guidance of their healthcare team.
The review found strong evidence that having a higher body weight after a breast cancer diagnosis increases a woman’s risk of dying.
It’s not yet clear why a higher body weight has this affect. Possible explanations of this link relate to differences in the following between women living with obesity compared with those who have a lower BMI:
All these factors are thought to interact in a way that increases the risk of breast cancer developing and may also be associated with poorer outcomes after a diagnosis. Obesity may also alter disease characteristics, so that those living with obesity develop breast cancer that is less treatable and more likely to spread. Further studies exploring the mechanisms that underpin the links between weight and breast cancer outcomes are much needed.
With recent improvements in cancer screening, diagnosis and treatment, women with breast cancer are living longer than before. Analysing the latest evidence helps us to understand how risk factors affect a woman’s long-term health after a breast cancer diagnosis and provide evidence to governments wanting to reduce the burden of cancer.
The findings strengthen the case for women with breast cancer, supported by their healthcare team, to make positive behaviour changes. This could include eating a healthier diet and being more physically active, both of which play a role in maintaining a healthy weight. Being a healthy weight also reduces the risk of other chronic diseases such as cardiovascular disease and diabetes.
Women living with and beyond breast cancer should always consult with their healthcare team before making any changes to their diet or physical activity routine.
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