For one of my classes this trimester, we had to do research on a topic of our choosing based on a fictitious case report we would write. However, I based this assignment and case on my own mother and seeing as it not only is close to my heart, but of particular interest to me, I thought it worthwhile sharing for those who may be similarly interested. I wanted to investigate intermittent fasting as a method of either preventing, or as an adjunctive therapy to treating breast cancer. I hope you find this read informative and take away some knowledge of value. While this may be a longer read than typical, it shows how evidence based our school’s curriculum is in a continued effort to further our profession.
I. Premise
Intermittent fasting is an eating pattern which cycles between periods of eating and periods of fasting. There are multiple time-based methods and variations, the most popular being the 16/8 method, where you fast for 16 hours of the day and eat in an 8-hour window (e.g. 12pm-8pm). Intermittent fasting has a central focus on when you eat, rather than what you eat, making it a desirable dietary habit for those who seek weight loss but often face challenges with healthy food choices and dietary habits. However, there are many reported benefits other than simply weightloss.
Due to the nature of eating in a time window, many people do report weight loss both from reduced caloric intake, but also from the metabolic state of ketosis prolonged fasting puts you in and encourages the body to use stored fast as energy rather than simply glucose and dietary sugars. This has been shown to increase insulin sensitivity, which in turn also reduces the risk for type 2 Diabetes Mellitus. Intermittent fasting has also been shown to increase brain-derived neurotrophic factor (BDNF), which supports brain function and mood, as well as potentially acting as a neuroprotective agent against diseases like Alzheimer’s and Parkinson’s.
One of the most potentially beneficial effects of intermittent fasting, however, is its ability to trigger autophagy, the cellular process by which the human body rids itself of damaged or dysfunctional cells as well as well as regenerating new ones, which is especially important when understood from the perspective of cancer prevention and even treatment.
Breast cancer is an increasingly common diagnosis, with 1 in 8 women in the US being diagnosed with it in her lifetime. In 2025, an estimated 316,950 women and 2,800 men will be diagnosed with invasive breast cancer, and an additional 59,080 new cases of non-invasive (in situ) breast cancer will be diagnosed (NBCF, 2025). The traditional treatment for breast cancer is chemotherapy, which is a combination of pharmaceuticals that can be given prior to, in adjunct to, or post operation. These drugs are extremely powerful and effective at reducing DNA synthesis and reducing cell mutations, but are often non-specific, wreaking destruction on not only damaged cells and DNA, but also healthy cells as well. This, alongside nasty side effects including, nausea, vomiting, loss of appetite, weight loss, hair loss and others, is a large reason why many patients are looking for alternatives for cancer treatment.
Intermittent fasting is being investigated for its use in adjunct with chemotherapy to treat cancer and prevent future reoccurrence due to the autophagic effects.
II. Case
Amy is a 57-year-old Caucasian female who initially presented to her plastic surgeon with the desire to get breast implants. As a preoperational precaution, her doctor has her go for a mammogram. After initial testing, there was an anomaly which led to the conduction of a biopsy to determine the nature of “lump.” Amy was diagnosed with astage 0 Ductal Carcinoma In Situ (DCIS). This was explained to her as “pre-cancerous” but did need to be addressed. She was then sent for a full-body MRI to check for any metastasis as well as genetic testing for the BRCA gene.
Both the MRI and genetic tests came back negative. She was given two main options: a lumpectomy with local radiation and potentially chemotherapy, or a double mastectomy. While she like the idea of a localized approach, the use of radiation would prevent her from getting the breast augmentation she had initially presented for, whereas the double mastectomy not only eliminated future risk of breast cancer, but could also be done alongside reconstruction.
She is strongly against the use of chemotherapy, and hesitant with the localized radiation, but also very scared of reoccurrence if she doesn’t get the double mastectomy and wanted to see if there were any alternative and more “natural” approaches to reducing future breast cancer risks.
III. Background Information
Breast cancer is a disease in which there is abnormal and unregulated cell growth in the breast tissue, which can occur in both men and women, although it is far more common in women. Breast cancer is classified by its location, stage, hormone receptor status and genetic markers, which all play a role in deciding the best treatment option. There are six main classifications of breast cancer:
- Ductal Carcinoma in Situ (DCIS) – Non-invasive; confined to ducts.
- Invasive Ductal Carcinoma (IDC) – Most common type; cancer spreads beyond ducts.
- Invasive Lobular Carcinoma (ILC) – Begins in lobules; can spread.
- Triple-Negative Breast Cancer (TNBC) – Lacks ER, PR and HER2 receptors; more aggressive.
- HER2-Postive Breast Cancer – Overexpresses HER2 protein; grows quickly but responds well to targeted therapy.
- Hormone Receptor Positive (ER/PR+) – Driven by estrogen or progesterone; often treatable with hormone therapy.
Typical signs and symptoms vary highly depending on the classification and progression of the cancer. Early-stage breast cancers often don’t have noticeable symptoms, reinforcing the critical nature of regular screenings like mammograms, but when present may include a lump in the breast or axilla (most common symptoms), change in breast size or shape, skin changes on the breast including dimpling known as peau d’orange, nipple changes like inversion or discharge, or simply pain.
Treatment Options
Surgery:
Lumpectomy- removes tumor and a small margin of surrounding tissue; breast is preserved.
Mastectomy- removes the entire breast; may be followed by reconstruction.
Lymph Node Removal- Sentinel lymph node biopsy or axillary lymph node dissection to check for spread.
Chemotherapy:
Goal is to kill growing cancer cells systemically; used either before surgery to shrink tumor or after surgery to destroy any remaining cancer cells. More commonly used for aggressive forms like TNBC or when the cancer has metastasized.
Radiation Therapy:
Destroys cancer cells in a targeted area using high-energy rays; often used after lumpectomy or mastectomy if lymph node involvement was detected.
Hormonal (Endocrine) Therapy: Blocks hormones that fuel ER-positive or PR-positive cancers.
Immunotherapy: Used specific drugs like Atezolizumab or Pembrolizumab with chemo to help the body’s immune system recognize and fight the cancer.
A Personal Choice
Breast cancer and its treatment is highly personalized and must be comanaged with a multidisciplinary team including oncologists, surgeons, radiation specialists and potentially even chiropractors and nutritionists in order to manage both the disease process and the side effects that come along with treatment.
Using intermittent fasting as a dietary intervention to stimulate autophagy may be a valuable adjunctive therapy in order to not only help fight a current cancer but reduce risk of future reoccurrence. Autophagy reduces the risk of DNA damage that can lead to cancer through clearing of mutated proteins and damaged organelles, reducing inflammation, and making cells more vulnerable to chemotherapy or radiation.
IV: Summary of Research
A total of three (3) study reviews were performed in an effort to provide a comprehensive overview of research applicable to PICO question criteria:
Study 1: Intermittent Fasting in Breast Cancer: A Systematic Review and Critical Update of Available Studies. Hierarchy of Study: Systematic Review.
Summary: This study is a systematic review of clinical research published between December of 2010 and October of 2022. The focus was younger women (all aged 27-28) with various stages of breast cancer as well as classifications including , II (HER2-/+), III (HER2-/+), IV, LUMINAL-A, LUMINAL-B (HER2-/+), and aimed to assess intermittent fasting’s (IF) effects on chemotherapy-related quality of life (QoL) toxicity, tumor response, recurrence, endocrine factors, and adverse events. After screening 468 articles, the researchers selected 10 human studies which they assessed using the Mixed Method Appraisal Tool (MMAT).
Results/Conclusions: The authors first found that IF was generally safe during chemotherapy. The markers of DNA and leukocyte damage was reduced in fasting groups, suggesting lower cytotoxicity. Additionally, the participants reports decreases in fatigue, nausea, and headaches, although this data is based on low-quality data. There were improved glycemic markers including lower serum glucose, insulin, and IGF-1 levels. Last, there was no clear evidence that IF influenced chemotherapy effectiveness, tumor shrinkage, or the rate of recurrence.
Discussion/Impression: This research is promising in terms of health markers and potential signs of DNA damage but is only relevant if my patient were to undergo chemotherapy. It does report that IF showed no clear or definitive evidence of influencing rate of recurrence, which was of particular interest to my patient. However, should my patient decide with her managing doctors to undergo chemotherapy, this source could be sound information to base an IF based diet for the purpose of reducing side effects of glycemic markers.
Study 2: Intermittent Fasting in the Prevention and Treatment of Cancer.
Hierarchy of Study: Review Article.
Summary: This study is a comprehensive narrative review of preclinical and clinical evidence on intermittent fasting (IF) and cancer prevention/treatment. This source addressed various IF regiments including time-restricted feeding (TRF), prolonged fasting (>24 hours) and fasting-mimicking diets (FMDs). It highlighted the mechanistic pathways (e.g. autophagy, reduced insulin/IGF-1, decreased inflammation) and evaluates both animal and human trials. In the early-phase human clinical trials, researchers measured chemotherapy side effects, DNA damage markers in white blood cells, tumor repones rates, metabolic markers (glucose, insulin, IGF-1), and patient-reported outcomes (quality of life, hunger, adherence).
Results/Conclusions: Results and conclusion are mixed as IF may reduce chemo toxicity and improve metabolic health, but no significant proof of tumor or survival benefits have been shown. The authors concluded IF should not yet be recommended during active cancer treatment outside of clinical trials, but may be considered safe for overweight/obese adults seeking weight management.
Discussion/Impression: This study, like the previous, indicates IF is a great potential option for managing the side effects of chemotherapy, but does not present any new or relevant information in respect to IF having significant impact on patient outcomes in terms of tumor growth or recurrence of cancer. They also were not a proponent of non-clinical trial usage compared to the first study which considered IF a generally safe practice with many positive benefits.
Hierarchy of Study: Systematic Review.
Summary: This study included a total of 10 studies, examining the effects of IF on treatment toxicities, patient symptoms quality of life, and metabolic parameters. The study classified toxicities as hematologic, gastrointestinal, therapy-related adverse events, quality of life symptoms as fatigue, nausea and general well-being, biological markers including DNA damage and immune changes, and metabolic effects including blood sugar and body composition.
Results/Conclusions: The IF regimens were generally well tolerated and reported to be safe for cancer patients. There were reduced fatigue and GI side effects, and soe studies also observed fewer hematologic toxicities like neutropenia. There was also improved quality of life symptoms reported such as improvements in energy and well-being, and even a reduction in off-target DNA damage in fasting patients undergoing chemo. Lastly, there was improvements in glucose control and better fat-to-lean mass ratio. While also preliminary, these results are promising for both the usage of IF for improved quality of life and reduction of side effects whilst undergoing cancer treatments like chemotherapy, as well as for the metabolic benefits.
Discussion/Impression: This study also reported improved quality of life reports in addition to better management of side effects and metabolic control.
All the of these studies showed that IF was generally regarded as a safe adjunctive therapy for patients undergoing active treatment for cancer. The largest benefits seemed to come from a reduction in negative side effects which are normally associated with traditional cancer treatment protocols like chemotherapy. There was also an improvement in metabolic markers like insulin sensitivity, fasting blood glucose, and IGF-1. However, there was no measurable or statistically significant results showing that IF had any effect on outcomes of patients suffering from cancer or breast cancer, with regards to survival or recurrence. Although this is discouraging, it is clear this research is still in its early phases and needs many more long term and rigorous controlled studies to adequately determine if there is an improvement in outcome for patients who stick with an IF diet.
References/Resources
Anemoulis M, Vlastos A, Kachtsidis V, Karras SN. Intermittent Fasting in Breast Cancer: A Systematic Review and Critical Update of Available Studies. Nutrients. 2023;15(3):532. Published 2023 Jan 19. doi:10.3390/nu15030532 https://pubmed.ncbi.nlm.nih.gov/36771239/
Breast cancer facts & stats 2024 – incidence, age, survival, & more. National Breast Cancer Foundation. (2025, June 12).
Clifton KK, Ma CX, Fontana L, Peterson LL. Intermittent fasting in the prevention and treatment of cancer. CA Cancer J Clin. 2021;71(6):527-546. doi:10.3322/caac.21694
Li Sucholeiki R, Propst CL, Hong DS, George GC. Intermittent fasting and its impact on toxicities, symptoms and quality of life in patients on active cancer treatment. Cancer Treat Rev. 2024;126:102725. doi:10.1016/j.ctrv.2024.102725
Marinac, C. R., Nelson, S. H., Breen, C. I., Hartman, S. J., Natarajan, L., Pierce, J. P., Flatt, S. W., Sears, D. D., & Patterson, R. E. (2016). Prolonged Nightly Fasting and Breast Cancer Prognosis. JAMA oncology, 2(8), 1049–1055. https://doi.org/10.1001/jamaoncol.2016.0164
Tiwari, S., Sapkota, N., & Han, Z. (2022). Effect of fasting on cancer: A narrative review of scientific evidence. Cancer Science, 113(10), 3291–3302. https://doi.org/10.1111/cas.15492
