Is Intermittent Fasting Worth the Weight?

Obesity and being overweight are the cause of a number of major health concerns including 13 types of cancer, including breast cancer. As a result, many seek out methods to help with weight management in an effort to reduce risk. Most recently, intermittent fasting (IF) has taken the spotlight as a method to help achieve this goal.

Unlike most diet plans IF does not focus as much on which foods you eat but rather when you choose to eat them. While there are a variety of IF methods possible, all are based on the idea of altering the time between fasting and eating. Some of the methods focus on reducing the period of time you eat in waking hours while others may focus on minimizing intake on alternate days. Intermittent fasting may be a way to reduce weight by creating a caloric deficit. However, in the short term, any approach used to reduce daily caloric intake can achieve this. In turn, maintaining a healthy body weight is associated with a reduced risk of a variety of health related issues including breast cancer.

Can intermittent fasting help fight against breast cancer?

Overweight and obesity can lead to insulin resistance which may be associated with increased risk for breast cancer in post-menopausal women. With this in mind, normalizing IF as a more standardized form of weight management may have potential in helping to reduce risk on a larger scale. Studies show some promise but much more extensive testing is needed to conclusively show this to be an effective measure.

In one study, researchers found one form of IF, focusing on limiting hours of intake as opposed to calories, may be associated with improved insulin sensitivity and decreased breast cancer risk. Though results were promising, it is important to note that this was conducted in a lab setting with mice (preclinical research). Long-term studies are necessary to determine if the same benefits are even possible in humans.

Prolonging nightly fasting has also been shown to be a potential strategy to reduce breast cancer . Researchers found that among an early-stage breast cancer population, those who fasted less than 13 hours per night were 36% more likely to have breast cancer recurrence compared to those that fasted more. It is important to note that information for this study was taken from participant diet recall making results dependent on the accuracy of what was reported. More testing is required to confirm this.

Early stage research in humans has also suggested that time-restricted eating may improve the effectiveness of certain cancer treatments by activating immune response in the body. These results were taken from a small study involving participants with different types of cancer (including breast cancer) following a very restrictive form of eating. Though there may be potential, more research on a larger scale is needed.

Is this type of eating right for everyone?

It is always a good idea to consult your medical provider before starting any diet. This is particularly true for those undergoing cancer treatment as the most the important thing is maintaining good nutrition. Periodic fasting is not appropriate for everyone, including:

  • People who are pregnant or breastfeeding
  • Those with Type 1 diabetes requiring insulin
  • Individuals who take medication with food
  • Anyone with disordered eating habits

The best diet plan is the one that works for you and can be sustained over time. IF may be an alternative way to jumpstart your weight loss journey. Focusing on a diet rich in whole foods such as fruits, vegetables, whole grains, and lean proteins are integral to our overall health and well-being.


1. Islami F, Goding Sauer A, Miller KD, et al. Proportion and number of cancer cases and deaths attributable to potentially modifiable in the United States. CA Cancer J Clin. 2018;68:31-54.

2. Van den Brandt PA, Ziegler RG, Wang M, et al. Body size and weight change over adulthood and risk of breast cancer by menopausal and receptor status: a pooled analysis of 20 prospective cohort studies. Eur J Epidemiol. 36(1):37-55, 2021.

3. De Cabo R and Mattson MP. Effects of intermittent fasting on health, aging, and disease. New England Journal of Medicine. 2019;381(26):2541-2551. doi: 10.1056/NEJMra1905136. Animal studies

4. Yoshida J, Eguchi E, Nagaoka K, Ito T, Ogino K. Association of night eating habits with metabolic syndrome and its components: a longitudinal study. BMC Public Health. 2018 Dec 11;18(1):1366. doi: 10.1186/s12889-018-6262-3. PMID: 30537972; PMCID: PMC6288903

5. Welton S, Minty R, O’Driscoll T, Willms H, Poirier D, Madden S, Kelly L. Intermittent fasting and weight loss: Systematic review. Can Fam Physician. 2020 Feb;66(2):117-125. PMID: 32060194; PMCID: PMC7021351.

6. Pan, K, Chlebowski, RT, Mortimer, JE, Gunther, MJ, Rohan, T, Vitolins, MZ, Adams-Campbell, LL, Ho, GYF, Cheng, T-YD, Nelson, RA. Insulin resistance and breast cancer and mortality in postmenopausal women in the Women’s Health Initiative. Cancer. 2020: 126: 3638- 3647.

7. Das, M., Ellies, L.G., Kumar, D. et al. Time-restricted feeding normalizes hyperinsulinemia to inhibit breast cancer in obese postmenopausal mouse models. Nat Commun 12, 565 (2021).

8. Marinac CR, Nelson SH, Breen CI, Hartman SJ, Natarajan L, Pierce JP, Flatt SW, Sears DD, Patterson RE. Prolonged Nightly Fasting and Breast Cancer . JAMA Oncol. 2016 Aug 1;2(8):1049-55. doi: 10.1001/jamaoncol.2016.0164. PMID: 27032109; PMCID: PMC4982776.

9. Vernieri, C., Fucà, G., Ligorio, F. et al; Fasting-Mimicking Diet Is Safe and Reshapes Metabolism and AntitumorImmunity in Patients with Cancer. Cancer Discov 1 January 2022; 12 (1): 90–107.