By maintaining a healthy weight throughout your life, you can reduce your risk of developing breast cancer after the menopause.

How likely am I to get breast cancer?

Breast cancer is the most common cancer in the UK. Overall, one in eight women develops the disease in their lifetime, but not everyone’s risk is the same.

Some people will have a higher or lower risk than others. Our chances of developing breast cancer depend on a combination of our genes and bodies, lifestyle and life choices and surrounding environment.

You cannot change some things that affect your risk, such as getting older. However there are other things you can change.

Maintaining a healthy weight throughout your life is one of the ways you can reduce your risk of getting breast cancer after the menopause.

Am I a healthy weight?

There are a few ways to check whether your weight is healthy. The most common way is by working out your Body Mass Index (BMI), using your weight and height. A healthy BMI is classified as between 18.5 to 24.9. If your BMI is less than 18.5, you may be underweight, and if your BMI is above 24.9, you may be overweight. If your BMI is over 30, you are obese. You can calculate your BMI on the NHS website

Although BMI is an easy and useful way for most people to assess whether their weight is healthy, BMI doesn’t work for everybody – it may not be an accurate way to assess weight for athletes, the elderly or pregnant women.

Your waist circumference can also be helpful for assessing your weight. For women, a waist circumference of up to 32 inches (88 cm) is considered healthy. A measurement of 32 to 35 inches (80cm to 88cm) is high, and a measurement of over 35 inches (88 cm) is very high.

Does my weight affect my risk of developing breast cancer?

By maintaining a healthy weight throughout your life, you can reduce your risk of developing breast cancer after the menopause (when your periods naturally stop). The effect of weight on breast cancer risk depends on whether or not you have been through the menopause, which is usually around the age of 50.

After the menopause:

Being overweight or obese after the menopause increases your risk of developing breast cancer.

In addition, putting on weight through adulthood increases your risk of developing breast cancer after the menopause. Importantly, the more weight you gain over the course of your adult life, the higher your breast cancer risk after the menopause.

Being obese when diagnosed with breast cancer can also increase the risk that your cancer will come back after treatment (recur) and reduce your chances of surviving the disease.

Before the menopause:

Being overweight or obese before the menopause may slightly reduce your risk of developing breast cancer, up to the point when you reach the menopause.

It’s important to note that breast cancer risk increases with age. The effect of weight on breast cancer risk is therefore of most importance after the menopause, when four out of five (80%) breast cancers occur.

Why does weight gain affect breast cancer risk?

The effect of weight on breast cancer risk is likely to be due to differences in the levels of the female sex hormones oestrogen and progesterone.

Although these natural hormones are important in the body, they can encourage some breast cancers to grow. For women who are overweight or obese after the menopause, the increased risk of breast cancer is likely to be due to a higher level of oestrogen in the body. After the menopause, the ovaries stop producing oestrogen, causing your monthly periods to stop. The body does continue to make some oestrogen at a much lower level than before, which is linked to the amount of body fat you have. The more fat tissue you have, the higher your levels of oestrogen are likely to be and this, in turn, increases your risk of breast cancer.

How much does my weight affect my risk?

The higher your BMI after the menopause the higher your risk of breast cancer will be. We can show this with the chart below. This shows how many women out of 100 will probably develop breast cancer after age 50, depending on their BMI.

For example:

  • In a group of 100 women with a BMI between 22.5 and 24.9 (the upper range of a healthy weight) about 8 or 9 will probably develop breast cancer after the age of 50.
  • In contrast, in 100 women with a BMI of 30 or more (which is obese), about 11 or 12 women will probably develop breast cancer.
  • Therefore, being obese leads to about 3 extra women out of every 100 developing breast cancer after the age of 50.

Breast cancer risk in women over 50 by body mass index (BMI)

Number of women out of 100 who will probably develop breast cancer gradually increases as BMI increases from <22.5 (7 out of 100) to >30 (11 or 12 out of 100)

Are there other benefits to maintaining a healthy weight?

Maintaining a healthy weight throughout your life reduces your risk of developing a variety of other health problems, including heart disease, stroke, type 2 diabetes, and several other types of cancer.

How can I keep my weight healthy?

Eating a balanced diet rich in fruit and vegetables, limiting sugary or fatty processed foods, eating and drinking the right amount (consuming only the calories your body needs), and being regularly physically active can help you to maintain a healthy weight.

We recommend that you speak with your doctor for advice on how to manage your weight and introduce good habits into your day-to-day life. You can also find information on the NHS Live Well website

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Information last reviewed: November 2013

Next review due: November 2016

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