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Breast Cancer Risk Factors You Can Change
A risk factor is anything that increases your chance of getting a disease, such as breast cancer. But having a risk factor, or even many, does not mean that you will get the disease.
Certain breast cancer risk factors are things you can change, such as diet and physical activity. Other risk factors involve personal or medical decisions, such as pregnancy or taking medicines that contain hormones.
Having excess body weight (overweight or obesity)
Having excess body weight (overweight or obesity) after menopause increases breast cancer risk.
Before menopause, a woman's ovaries make most of the estrogen in the body. Only a small amount of estrogen is made by fat tissue. After menopause, the ovaries stop making estrogen. Most estrogen then comes from fat tissue. Having more fat tissue after menopause can raise estrogen levels and increase the chance of getting breast cancer.
People who have excess body weight also tend to have higher blood insulin levels. Higher insulin levels have been linked to some cancers, including breast cancer.
Still, the link between weight and breast cancer risk is complex. For example:
- The risk of breast cancer after menopause is higher for women who gained weight after menopause.
- If you have excess body weight (overweight or obesity) before menopause, the risk is lower.
The reasons for this aren’t exactly clear.
Weight might also have different effects on different types of breast cancer. For example:
- Having excess body weight after menopause is more strongly linked with a higher risk of hormone receptor-positive breast cancer.
- Some research suggests that having excess body weight before menopause may increase your risk of the less common triple-negative breast cancer.
Avoiding weight gain with age may lower the risk of breast cancer. Losing even a small amount of weight in adulthood may lower the risk of breast cancer in people with excess body weight as they age. The American Cancer Society recommends staying at a healthy weight throughout your life. One way to do this is to balance what you eat and drink with physical activity.
Physical activity
Increasing physical activity levels can reduce the risk of breast cancer. It is not exactly clear how physical activity might reduce breast cancer risk. It might be because physical activity affects inflammation and hormone levels.
The American Cancer Society recommends that adults get 150 to 300 minutes of moderate-intensity activity or 75 to 150 minutes of vigorous-intensity activity each week. Or you can get a combination of these. Doing 300 minutes of activity or more is ideal.
Alcohol use
Drinking alcohol increases the risk of breast cancer. It also increases the risk of other types of cancer such as cancers of the head and neck and cancer in the digestive system.
The risk increases the more alcohol you drink. For example, drinking 2 alcoholic beverages a day increases breast cancer risk more than drinking 1 alcoholic beverage a day.
No amount of alcohol is completely safe. It’s best not to drink alcohol. If you choose to drink, women should have no more than 1 a day.
Smoking tobacco
Smoking tobacco increases the risk of many different types of cancer. The link between smoking and breast cancer has been difficult to study, because many people who smoke also drink alcohol, which increases breast cancer risk. Some studies suggest that smoking alone may also increase the risk of breast cancer.
See Health Risks of Smoking Tobacco to learn more about how smoking can affect your health.
Pregnancy
There are 2 pregnancy-related situations that slightly increase the risk of breast cancer:
- Never being pregnant
- Having a first pregnancy at age 35 or later
Women in these situations have a slightly higher breast cancer risk overall when compared to women who had their first child in their 20s. Women who have had many pregnancies or first became pregnant at a young age have lower risk for breast cancer.
Still, the effect of pregnancy and childbearing on breast cancer risk is complex. For example, the risk of breast cancer is higher for the first few years after having a child. Then risk lessens over time. The cause of this is unknown, but it is thought this might be due to hormonal effects on the breast tissue during pregnancy and after birth.
Breastfeeding
Most studies suggest that breastfeeding may slightly lower breast cancer risk, especially if it continues for a year or more. But this has been hard to study in countries like the United States where breastfeeding for this long is uncommon.
A possible explanation for this effect is that breastfeeding can delay the return of the menstrual cycle after pregnancy. This reduces a woman’s total number of lifetime menstrual cycles. This is the same as starting menstrual periods at a later age or going through early menopause.
Newer studies suggest that breastfeeding for any period of time may be protective against a certain type of breast cancer called hormone receptor-negative breast cancer. This type of cancer is more common in younger women. More studies are needed to understand this effect.
Hormone treatments
Hormone treatments, such as estrogen or progesterone, may be recommended by your care team to:
- Regulate menstrual cycles
- Treat symptoms like heavy bleeding
- Replace hormones that the body is no longer making in the case of premature ovarian insufficiency or menopause
- Be a part of gender-affirming care
These treatments can help support health or manage symptoms. However, hormone treatments may increase the risk of developing breast cancer in the future.
Some birth control methods use hormones. This might increase breast cancer risk during use and for a few years after stopping them.
Oral contraceptives: Some studies have found that women using oral contraceptives (birth control pills) have a slightly higher risk of breast cancer than women who have never used them. Once the pills are stopped, this risk seems to go back to normal within a few years.
Birth control shots: Some studies have suggested that getting long-acting progesterone shots (such as Depo-Provera) every 3 months for birth control might increase breast cancer risk. But not all studies have found this.
Birth control implants, intrauterine devices (IUDs), skin patches, vaginal rings: These forms of birth control also use hormones, which might affect breast cancer risk. Some studies have suggested a link between the use of hormone-releasing IUDs and breast cancer risk. But very few studies have looked at the use of birth control implants, patches, and rings and breast cancer risk.
Hormone replacement therapy (HRT) works by replacing the hormones your ovaries no longer make. It comes in different forms This treatment may be suggested for women experiencing moderate to severe symptoms of perimenopause and menopause, including hot flashes and changes in mood. These replacement hormones include estrogen and progesterone.
There are 2 main types of hormone therapy:
- Combined hormone therapy is prescribed for women who still have a uterus. It usually includes estrogen and progesterone. Progesterone is needed because estrogen alone can increase the risk of cancer of the uterus.
- Estrogen replacement therapy (ERT) is prescribed for women who no longer have a uterus (hysterectomy). In this case, estrogen alone can be used. You might also hear this called estrogen therapy (ET).
In the past, HRT carried a black box warning that included a higher risk of breast cancer. However, newer studies suggest this risk is much lower than previously thought. This black box warning was removed in 2025.
Still, the impact of hormones on the risk of breast cancer is complex. Many factors should be considered before starting HRT treatments. If you decide to use HRT, it should be in a way that matches your symptoms, personal and family health history, and personal goals.
Some people may choose to use the lowest effective dose for as short a time as possible. Others may choose to use hormone therapy for longer periods.
Things to think about when choosing HRT:
- How much do your menopause symptoms bother you?
- What is your personal risk of breast, endometrial, and ovarian cancer?
- Will hormone therapy change that risk?
- Do you have other serious health problems or risks that should be considered when talking about hormone therapy with your care team? (heart disease, stroke, serious blood clots or increased risk of these problems)
- What type and dose do your doctor recommend?
- What other medicines might help treat your menopausal symptoms instead?
A higher risk of breast cancer can be seen in women who use:
- HRT for a long time
- Certain types of HRT
- Higher doses of HRT
- HRT after the age of 60
However, in many women HRT can be used safely. But it is important to use HRT only after an evaluation with your healthcare team. And it is important to understand the risks and benefits of the treatment.
Talk with your care team about options to treat menopausal symptoms without hormones if you have concerns about HRT or HRT is not a good option for you.
To learn more, see Menopausal Hormone Therapy and Cancer Risk.
Transgender women on hormone therapy have a higher risk of breast cancer than cisgender men. But they have lower risk of breast cancer than cisgender women. This risk may be higher in long-term use or at higher doses.
Transgender men on testosterone therapy have a lower risk of breast cancer than cisgender women. But they have a higher risk than cisgender men.
More research is needed to understand the risks of the use of hormone therapy for gender-affirming care.
More resources
Learn more about risk factors for breast cancer.
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- References
Developed by the American Cancer Society medical and editorial content team with medical review and contribution by the American Society of Clinical Oncology (ASCO).
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Last Revised: June 11, 2026
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