October is Breast Cancer Awareness month. You wear pink, self-check, and get your annual mammogram, but none of these actions actually protect your breasts.

We know there are foods to protect against cancer... but what about not eating? Early research suggests that intermittent fasting (sometimes referred to as interval fasting, or IF), a cycle between periods of eating and fasting, might help  and possibly even prevent it from coming back if you’ve already been treated. The jury is still out on the effectiveness of IF, but it's an interesting subject for further study.

However, we want to start by saying that caution is advised: please talk with your doctor or nutritionist to determine if intermittent fasting is safe for you.

If you have safety concerns, a Gennev menopause-certified gynecologist can give you a trusted opinion, and determine if fasting is right for you. Book an appointment with a doctor here.

The facts on fasting and cancer

Fasting, abstaining from food, is nothing new for many of us.

Maybe you’ve fasted for religious reasons. Whether you’re Muslim, Catholic, Jewish, Buddhist, Hindu, or another faith, most religions embrace fasting as a way to spiritually cleanse and purify.

Or perhaps you’ve fasted for a medical procedure, like that colonoscopy you’ve been putting off.

We’ve written about intermittent fasting during menopause on the Gennev blog before, and it may be easier than you think—without the stress of holidays or gut-clearing laxatives.

Why is breast cancer a big concern for menopausal women?

According to the National Institute of Health, 1 in 8 U.S. women will be diagnosed with a form of breast cancer at some point in their lives. Breast cancer in women represents 15.2% of all new cancer diagnoses, period.

Aging increases cancer risk overall. Your likelihood of breast cancer goes up sharply in your early 40s and into menopause, with peak risk during your 60s and 70s. Black women see even higher breast cancer occurrences than white women once they enter their late 50s.


Can intermittent fasting for cancer prevention work?

More research needs to be done to determine if fasting works to reduce risk, but at this point, it appears it may have to do with blood sugar and circadian rhythm.

Researchers followed the eating habits of more than 2400 women with early-stage invasive breast cancer over a 12-year period; the study did not include women with diabetes.

Women who fasted for fewer than 13 hours each night were 36% more likely to have their cancer return than the women who fasted more than 13 hours, though mortality rates remained the same for both groups.

The longer the women fasted overnight, the more benefits they saw.

Regardless of the duration of fast, eating after 8 p.m. was associated with a significant increase in BMI and inflammation, both risk factors for cancer.

For many women, fasting decreases the overall calories consumed, which improves weight and inflammation.

However, even people who do not decrease calorie consumption through fasting see a difference in glucose metabolism: fasting causes an increase in insulin sensitivity.

Insulin is tied to breast health.

The drop in estrogen in our bodies during menopause leads to a decrease in insulin effectiveness.

When you eat, your digestive tract breaks down carbohydrates into sugar (glucose) and releases it into your blood.

Your cells need insulin, a hormone produced in the pancreas, to bring in glucose from the bloodstream to use as energy. Whatever glucose isn’t used is stored as fat.

Between meals, insulin levels drop and your body releases sugar stored in fat cells as energy. When fasting, your body is able to sustain low levels of insulin and blood sugar long enough to burn fat.

If your insulin isn’t working the way it should, your cells can’t bring in glucose, so this glucose turns into fat or stays in your bloodstream. For example, people with type 2 diabetes can make insulin, but their bodies can’t utilize it properly.

Women who have been diagnosed with type 2 diabetes have a 23% higher incidence of breast cancer compared to women without diabetes, and scientists are starting to understand why: there may be a link between breast cancer and hyperglycemia (high blood sugar) and insulin resistance (ineffective use of insulin).

Intermittent fasting may help you get around the increase in insulin resistance (and thus increased blood sugar) that comes with aging to protect your breasts.

Nighttime fasting synchronizes also with our body’s natural circadian rhythm, our 24-hour internal clock.

Night shift workers may have an increased incidence of breast cancer because their activities are out of sync with their circadian rhythm. If you’ve ever worked nights, you know how difficult it can be to eat or go to work when your body is sending signals for sleep.

Nighttime eating has long been associated with obesity and diabetes, and it may be about more than just insulin: eating late at night can give you insomnia or disrupt your sleep, too.

Did you know there’s a link between quality of sleep and breast cancer?

By avoiding food after 8 p.m. you send your body the right signals.

Fasting starves cancer cells.

Finally, fasting ramps up our body into protection mode, which may have benefits for women undergoing chemotherapy for breast cancer. Even better, scientists theorize that fasting does not have the same protective impact on cancer cells, which makes them more vulnerable to treatment.

Again, it hasn't been definitively proven that intermittent fasting is effective, so especially if you're undergoing treatment, check with your doctor before changing your diet.

Ways to fast

More research still needs to be done on the long-term benefits of fasting but following a healthy intermittent fasting schedule won’t hurt you.

While there are all sorts of trendy fasts out there for weight loss, doctors at UCSF recommend two methods for cancer prevention.

Eat during a specific window. Known as restricted nighttime feeding, 16:8 fasting, or the Leangains protocol, limiting your food intake to a specific 8- to 12-hour window during the day and fasting overnight is the most approachable type of intermittent fast for most people. Aim for at least 13 hours of fasting.

This can be as easy as eating dinner before 8 p.m. and skipping breakfast. You’re allowed to drink black coffee, tea, water, and other non-caloric beverages during the fasting period.

Alternate day fasting. This is exactly what it sounds like: you eat normally every other day and fast on the alternate. Most sources recommend consuming around 25% of your usual calories on the fasting day. The drawback: eating every other day is unsustainable long-term for most of us.

Tips for intermittent fasting cancer prevention

No matter which fasting plan you explore, the following tips can help keep you satiated—and sane:

  • Stay hydrated. Be sure to drink plenty of water; our bodies sometimes interpret thirst as hunger, and dehydration is, in general, bad for you.
  • Eat healthy, high-fiber, high-protein foods. These foods fill you up and give you the nutrients you need to sustain energy and health.
  • Avoid watching TV. If you’re hungry or thinking about food, that burger advertisement on the nightly news is going to hit you a lot harder.
  • Try tea or black coffee for energy dips. The caffeine will give you an extra boost of energy and mental clarity.
  • Keep up your exercise routine. If you’re fasting with weight loss as a secondary benefit, maintaining your exercise routine can safeguard against losses in muscle mass and bone density. If you’re practicing alternate day fasting, you might find that you prefer working out on your fast day; save your allotted daily calories for after the gym.
  • Stay busy. While it may seem counter-intuitive to commit to meetings or activities while hungry, you might just welcome the distraction.

Who shouldn’t fast

Intermittent fasting is not for everyone, and if you fall into one of the following groups, you should avoid fasting or approach it with caution and medical oversight.

  • Women with diabetes. Skipping meals or cutting calories is risky for women who already have issues regulating blood sugar.
  • Women with a history of eating disorders, like binge eating, anorexia, or bulimia. This may come as a surprise to those of us who thought we left disordered eating in our 20s: up to 13% of women experience an eating disorder in midlife. Any shift in your diet may trigger an unhealthy relationship with food.
  • Women who take medications for heart disease or blood pressure. Intermittent fasting may lead to dangerous electrolyte abnormalities.

Other things to do for breast health in midlife

More research still needs to be done on the benefits of intermittent fasting, but these breast best practices (say that ten times fast) will always help.

  • Although there are a lot of mammogram myths out there, they are the best way to detect breast cancer early. If breast cancer is caught early, it can be cured. Yes, we know that mammograms are no fun, but compared to cancer, they’re nothing to be afraid of. Seriously. Get a yearly mammogram once you hit 40.
  • Breast self-exams. Self-checks for lumps are not a substitute for a mammogram, as they don’t catch small growths, but we still encourage people with breasts to ‘practice breast self-awareness.’
  • Avoid alcohol. Aim for fewer than three drinks per week or teetotal altogether.
  • Get enough sleep. As we mentioned previously in this post, poor sleep hygiene may be linked to breast cancer.
  • Exercise and eat right. A recent study published by the American Association for Cancer Research suggests that the combination of exercise and preventing weight gain can slow tumor growth, prevent metastasis, and improve overall survival. The American Institute of Cancer Research recommends a diet high in vegetables, fruit, and grains and low in sugar. A plant-based diet full of anti-inflammatory foods, low glycemic starches, and healthy fats is even better.

Have you tried intermittent fasting? We want to hear from you! Share your experience or tips in the comments below or join the conversation in the Gennev community forums.


Helen Pitlick

A seasoned communicator with a master's degree in digital media to back it all up, Helen Pitlick loves to create content that helps women feel more confident at all stages of their lives. When she's not in front of her laptop, Helen enjoys pottery, pretending to play soccer, and hanging out with her dog.



Shannon Perry

October 23, 2019
Director of Programming & Media

Medically Reviewed By

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