Does Intermittent Fasting Prevents Cancer Recurrence?

Intermittent fasting (IF) has garnered significant attention in recent years. Numerous studies have demonstrated its efficacy and safety in weight loss. Additionally, IF has shown promise in improving metabolic and neurological conditions. But can intermittent fasting play a role in combating breast cancer? Is there sufficient data to incorporate this dietary approach into survivorship programs for breast cancer patients? Let’s explore the evidence.
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‍Historical Perspective on Fasting
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‍Fasting has been practiced for centuries, with its healing properties documented since ancient Greece. Hippocrates recommended fasting for certain diseases and infections, while philosophers like Plato and Aristotle, as early as 800 BCE, employed fasting to enhance cognition and mental clarity. In the 15th century, Paracelsus, regarded as one of the fathers of modern medicine, stated, “Fasting is the greatest remedy—the physician within.”By the mid-1800s, physician E.H. Dewey emphasized in The True Science of Living that many diseases originated from excessive eating. He is considered the inventor of the “ No Breakfast Plan”.  Upton Sinclair further popularized fasting in the early 20th century with the book The Fasting Cure, asserting that fasting could treat ailments such as cancer, tuberculosis, asthma, syphilis, and the common cold. More recently, fasting gained attention when Angus Barbieri fasted for 382 days in the 1960s, losing 125 kg. 
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‍Scientific Interest and Research Trends
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‍Over the past decade, scientific interest in fasting, particularly intermittent fasting, has surged. A bibliometric analysis indicates that from 2000 to 2016, research on intermittent fasting grew steadily, averaging 25 publications annually. Between 2017 and 2020, this figure rose sharply to 167 publications per year, reflecting intensified research activity.
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‍Mechanisms Linking IF and CancerInsulin and Insulin-like Growth Factor-1 (IGF-1)
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‍Insulin and IGF-1 are anabolic hormones that promote cell growth and energy storage. When we eat, insulin and IGF-1 levels rise, stimulating cell proliferation, preventing cell death(apoptosis), and promoting the formation of new blood vessels via vascular endothelial growth factor (VEGF). Cancer cells exploit these pathways to sustain uncontrolled growth, evade apoptosis, and enhance vascularization. This process enables cancer cells to thrive on glucose while benefiting from aging immune cells that fail to suppress malignancies effectively.
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‍Weight Loss and Hormonal Regulation
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‍Intermittent fasting-induced weight loss can lower the production of sex hormones such as estrogen and testosterone, which can play a major role in breast cancer pathogenesis. Approximately 70% of breast cancers are estrogen-driven, while some hormone receptor-negative cancers are fueled by testosterone. IF does not directly decrease these hormones but reduces adipose tissue, decreasing the conversion of androgen hormones to estrogen, and lowering the overall hormone levels. This conversion process is called aromatization.
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‍Reduction of Oxidative DNA Damage
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‍Chronic inflammation contributes to cellular damage and cancer development. IF has been shown to reduce systemic inflammation, lower pro-inflammatory markers, and mitigate DNA damage, all of which may contribute to cancer prevention and improve overall health.

‍Clinical Evidence Supporting IF in Breast Cancer Patients
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‍Current data suggest that IF may enhance the efficacy of conventional breast cancer treatments. Studies indicate that patients undergoing chemotherapy who fast around treatment days experience fewer side effects. Fasting-mimicking diets (FMDs) have also demonstrated an ability to enhance breast cancer cells' sensitivity to chemotherapy. However, these studies were conducted in multiple institutions with small sample sizes (<200 patients), warranting further large-scale trials.A systematic review screened 468 articles, with 10 studies included in the final analysis. The findings indicated that 14-hour daily intermittent fasting improved fatigue, enhanced the tolerability of systemic therapy, and may facilitate DNA repair.The Women’s Healthy Eating and Living (WHEL) Study provided compelling evidence regarding IF’s potential impact on breast cancer recurrence. This study included 2,413 women with early-stage breast cancer. Those who fasted for less than 13 hours per night had a 36% higher risk of breast cancer recurrence compared to those who fasted longer. While overall survival rates remained the same, longer fasting periods were associated with improved sleep quality, supporting the notion that late-night eating disrupts circadian rhythms and metabolic regulation, potentially increasing cancer risk.
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‍Practical Implementation of Intermittent Fasting
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‍Although intermittent fasting offers potential health benefits, its widespread adoption in clinical settings requires further investigation. IF optimizes metabolism, enhances anti-aging cellular mechanisms, and improves chronic inflammatory processes. However, prolonged fasting can lead to electrolyte imbalances, muscle loss, and increased stress hormones such as cortisol, which may counteract its benefits.Adherence is also a key consideration. Individuals with physically demanding jobs or cognitively intensive work may struggle with prolonged fasting periods.
A practical approach involves starting with one to two days of intermittent fasting per week. The WHEL study suggests that a 13-hour fasting window reduces breast cancer recurrence. So you fast 13-14 hours and can eat within a 10-11 hour window.  If well-tolerated, patients may gradually increase fasting frequency over time.

Conclusion
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‍Intermittent fasting is a promising adjunct to a healthy lifestyle. While more robust data is needed before implementing IF as a standard protocol for all breast cancer patients, existing evidence supports its role in metabolic optimization, inflammation reduction, and cancer prevention. IF should be considered alongside other lifestyle modifications, such as a Mediterranean diet rich in fruits, vegetables, olive oil,  lean proteins, regular exercise, and psychological stress management.By incorporating IF as part of a holistic approach to health, individuals may experience improved focus, mental clarity, and overall well-being.
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