For thousands of years, people across the world have fasted for religious and spiritual reasons. Today, scientists are discovering that fasting, the practice of going without food for specific periods, may offer real health benefits, particularly when it comes to preventing cancer. This article explores the latest research on how fasting works in our bodies and why it might be a powerful tool against cancer.
Fasting in world faiths
Fasting is deeply woven into the spiritual fabric of many faiths. Muslims fast during the month of Ramadan as a religious obligation, abstaining from food and drink from dawn to sunset for 30 days. Many Muslims also voluntarily fast for six additional days in the following month of Shawwal, and some follow the practice of fasting every Monday and Thursday throughout the year.
Christians observe fasting during Lent, a 40-day period of prayer and reflection leading up to Easter, with Ash Wednesday and Good Friday being the primary fasting days. Orthodox Christians practice even more extensive fasting periods, including the Nativity Fast, Apostles Fast, and Dormition Fast, along with fasting every Wednesday and Friday.
In Judaism, Yom Kippur stands out as a 25-hour complete fast, considered the holiest day of the Jewish year. Jews also observe Tisha B’Av, commemorating the destruction of the Temple, along with several minor fasts, including the Fast of Esther, the Fast of Gedaliah, the 17th of Tammuz, and the 10th of Tevet, which run from sunrise to sunset.
Hindus practise Ekadashi fasting on the eleventh day of each lunar phase, approximately twice a month, as well as during major festivals like Maha Shivaratri, Navratri, and Karwa Chauth. Hindu fasting practices vary widely, ranging from strict water-free fasts to consuming only fruits, milk, or specific non-grain foods.
What makes this especially relevant today is that fasting comes in many forms beyond these religious practices. Some people practise intermittent fasting, which means eating only during certain hours each day. Others practice periodic fasting, which involves going without food for longer stretches. Whatever the approach, scientists are finding that when we fast, our bodies undergo remarkable changes that may help protect us from cancer. The ancient wisdom of fasting traditions is now being validated by modern science.
Changing your body’s fuel system
One of the most important ways fasting may prevent cancer is by changing the type of fuel your body uses. Normally, our cells run on sugar from the food we eat. But when we fast, our bodies switch to burning fat instead. This shift has a powerful effect on certain hormones and proteins in our blood.
Two key players here are insulin and a protein called insulin-like growth factor-1, or IGF-1. Both of these tell cells to grow and multiply. That is fine for healthy cells, but cancer cells also love these signals. They use them to grow faster. When we are overweight or eat too much, our insulin and IGF-1 levels stay high, which scientists have linked to an increased risk of breast, colon, and prostate cancer.1
When you fast, your insulin and IGF-1 levels drop. This creates an environment where normal, healthy cells become more resilient, but cancer cells, which are essentially addicted to constant fuel and growth signals, struggle to survive.2,3 Recent research published in 2025 confirms that fasting creates what scientists call differential stress resistance, a state where normal cells are protected while cancer cells become vulnerable.4,5
Activating your body’s cleanup crew
Your cells have a built-in cleaning system called autophagy, which literally means self-eating. This process breaks down and recycles damaged parts of cells, like old machinery getting hauled away from a factory. When autophagy does not work properly, damaged components pile up, and this can lead to DNA damage and eventually cancer.6
Fasting is one of the most powerful natural triggers of autophagy. When you fast, your body kicks this cleaning process into high gear, removing cellular debris that could otherwise contribute to cancer development.7,8 Multiple studies from 2024 and 2025 have shown that autophagy activated by fasting can help prevent the early stages of cancer by maintaining cellular quality control.9,10,11
A study published in 2025 in the International Journal of Molecular Sciences found that intermittent fasting significantly enhances autophagy in a way that specifically targets damaged cells while protecting healthy ones.12 Think of it as your body’s quality control system working overtime to catch problems before they become cancer.
Cooling down chronic inflammation
Chronic inflammation is like a fire smouldering in your body that never quite goes out. While short-term inflammation helps fight infections and heal injuries, long-term inflammation creates an environment where cancer can thrive. It is like providing cancer cells with a welcoming neighbourhood to set up shop and grow.13
Research shows that fasting can significantly reduce inflammation throughout the body. One study found that people who practised intermittent fasting had much lower levels of inflammatory chemicals in their blood.14 More recent research from 2025 confirms that fasting shifts the immune system toward a more anti-inflammatory state.15,16 By dampening this chronic inflammation, fasting essentially removes one of cancer’s key allies. It is taking away the fuel for the fire that helps cancer cells survive and spread.
Rebooting your immune system
Your immune system is your body’s defence force against cancer. It includes special cells called T-cells and natural killer cells that patrol your body looking for damaged or abnormal cells to destroy. When this system works well, it catches cancer cells early and eliminates them before they become a problem.
Here is where fasting gets really interesting: research shows it can actually reboot your immune system. A pivotal 2014 study showed that during fasting, old and damaged immune cells essentially get retired. When you start eating again, your body produces fresh, healthy immune cells to replace them.17
Even more exciting is recent research from Memorial Sloan Kettering Cancer Centre; scientists found that fasting trains natural killer cells to use fat as fuel instead of sugar. This is crucial because tumours contain a lot of fat, creating a hostile environment for most immune cells. But fasted natural killer cells, having learned to burn fat, can actually survive and function better in this environment, making them more effective cancer fighters.18
What recent studies in people show
While most of the detailed research has been done in laboratory animals, we are now seeing promising results in human studies too. In 2020, a major study looked at women who had been treated for breast cancer. They found that women who fasted for 13 or more hours each night, a simple form of time-restricted eating, had a 36 per cent lower risk of their cancer coming back compared to women who fasted less.19 This is a significant finding because it suggests that something as simple as not eating late at night could make a real difference.
More recent research from 2024 through 2025 continues to support these findings. A comprehensive systematic review published in Nutrition Reviews in 2025 analysed multiple studies and found that time-restricted eating produces beneficial metabolic changes even without significant weight loss, suggesting the timing of eating matters independent of calorie reduction.20
Studies of people who fast for cultural or religious reasons, such as during Ramadan, have also shown favourable changes in cancer-related markers in the blood, including reduced inflammation and oxidative stress.21,22 A 2025 study found that intermittent fasting can even change gut bacteria in ways that reduce cancer risk, particularly for colorectal cancer.23
The bottom line
The scientific evidence on fasting and cancer prevention is growing stronger every year. Fasting appears to work through multiple pathways simultaneously. It lowers hormones and growth factors that cancer cells depend on. It activates cellular cleanup mechanisms that remove damaged components. It reduces chronic inflammation that helps cancer grow. And it rejuvenates the immune system’s cancer-fighting abilities.
While we still need more long-term studies in humans to establish specific guidelines, the current evidence is compelling. Fasting is not a fad or miracle cure. It is a scientifically grounded approach that leverages your body’s natural protective mechanisms.24
In the month of Ramadan, it is worth appreciating that this ancient spiritual practice may offer profound health benefits. The convergence of faith and science reminds us that sometimes our traditional practices align beautifully with what modern research is discovering.
Looking ahead, personalised fasting programmes, tailored to individual genetics and health status, may become an important part of cancer prevention strategies. They offer a powerful, low-cost tool alongside traditional advice about diet and exercise.25
Endnotes
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2. de Cabo, R., & Mattson, M. P. (2019). Effects of Intermittent Fasting on Health, Aging, and Disease. The New England journal of medicine, 381(26), 2541–2551.
3. Faris, MoezAlIslam Ezzat; Alkawamleh, Dania Husam; Madkour, Mohamed Ibrahim. Unraveling the impact of intermittent fasting in cancer prevention, mitigation, and treatment: A narrative review. Journal of Nutritional Oncology 10(2):p 29-39
4. Fatima, G., Mehdi, A. A., Fedacko, J., Hadi, N., Magomedova, A., & Mehdi, A. (2025). Fasting as Cancer Treatment: Myth or Breakthrough in Oncology. Cureus, 17(3), e81395.
5. Blaževitš, O., Di Tano, M., & Longo, V. D. (2023). Fasting and fasting mimicking diets in cancer prevention and therapy. Trends in cancer, 9(3), 212–222.
6. Levine, B., & Kroemer, G. (2008). Autophagy in the pathogenesis of disease. Cell, 132(1), 27–42.
7. Liu, S., Yao, S., Yang, H., Liu, S., & Wang, Y. (2023). Autophagy: Regulator of cell death. Cell death & disease, 14(10), 648.
8. Antunes, F., Erustes, A. G., Costa, A. J., Nascimento, A. C., Bincoletto, C., Ureshino, R. P., Pereira, G. J. S., & Smaili, S. S. (2018). Autophagy and intermittent fasting: the connection for cancer therapy?. Clinics (Sao Paulo, Brazil), 73(suppl 1), e814s.
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10. Mao, Y., Xia, Z., Xia, W., & Jiang, P. (2024). Metabolic reprogramming, sensing, and cancer therapy. Cell reports, 43(12), 115064.
11. Mindikoglu, A. L., Abdulsada, M. M., Jain, A., Choi, J. M., Jalal, P. K., Devaraj, S., Mezzari, M. P., Petrosino, J. F., Opekun, A. R., & Jung, S. Y. (2020). Intermittent fasting from dawn to sunset for 30 consecutive days is associated with anticancer proteomic signature and upregulates key regulatory proteins of glucose and lipid metabolism, circadian clock, DNA repair, cytoskeleton remodeling, immune system and cognitive function in healthy subjects. Journal of proteomics, 217, 103645.
12. Wolska, W., Gutowska, I., Wszołek, A., & Żwierełło, W. (2025). The Role of Intermittent Fasting in the Activation of Autophagy Processes in the Context of Cancer Diseases. International journal of molecular sciences, 26(10), 4742.
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15. Khan, D., & Mishra, A. (2025). Intermittent Fasting- A Paradigm Shift In Cancer Prevention and Treatment: A Scoping Review. Indonesian Journal of Cancer, 19(2), 322 – 330.
16. Rahbar, A. R., Safavi, E., Rooholamini, M., Jaafari, F., Darvishi, S., & Rahbar, A. (2019). Effects of Intermittent Fasting during Ramadan on Insulin-like Growth Factor-1, Interleukin 2, and Lipid Profile in Healthy Muslims. International journal of preventive medicine, 10, 7.
17. Cheng, C. W., Adams, G. B., Perin, L., Wei, M., Zhou, X., Lam, B. S., Da Sacco, S., Mirisola, M., Quinn, D. I., Dorff, T. B., Kopchick, J. J., & Longo, V. D. (2014). Prolonged fasting reduces IGF-1/PKA to promote hematopoietic-stem-cell-based regeneration and reverse immunosuppression. Cell stem cell, 14(6), 810–823.
18. Delconte, R. B., Owyong, M., Santosa, E. K., Srpan, K., Sheppard, S., McGuire, T. J., Abbasi, A., Diaz-Salazar, C., Chun, J., Rogatsky, I., Hsu, K. C., Jordan, S., Merad, M., & Sun, J. C. (2024). Fasting reshapes tissue-specific niches to improve NK cell-mediated anti-tumor immunity. Immunity, 57(8), 1923–1938.e7.
19. 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.
20. Stringer, E. J., Cloke, R. W. G., Van der Meer, L., Murphy, R. A., Macpherson, N. A., & Lum, J. J. (2025). The Clinical Impact of Time-restricted Eating on Cancer: A Systematic Review. Nutrition reviews, 83(7), e1660–e1676.
21. Mindikoglu, A. L., Abdulsada, M. M., Jain, A., Choi, J. M., Jalal, P. K., Devaraj, S., Mezzari, M. P., Petrosino, J. F., Opekun, A. R., & Jung, S. Y. (2020). Intermittent fasting from dawn to sunset for 30 consecutive days is associated with anticancer proteomic signature and upregulates key regulatory proteins of glucose and lipid metabolism, circadian clock, DNA repair, cytoskeleton remodeling, immune system and cognitive function in healthy subjects. Journal of proteomics, 217, 103645.
22. Rahbar, A. R., Safavi, E., Rooholamini, M., Jaafari, F., Darvishi, S., & Rahbar, A. (2019). Effects of Intermittent Fasting during Ramadan on Insulin-like Growth Factor-1, Interleukin 2, and Lipid Profile in Healthy Muslims. International journal of preventive medicine, 10, 7.
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