Fasting to support cancer treatment

Fasting is to abstain from food and drinks other than water for a period of time.

Personally, I am a fan of fasting lately with myself going through 3 rounds of 5:2 intermittent fasting a month ago. Despite the difficulty of having to abstain from food and drinks for 2 full days a week, the experience is quite exhilarating. I lost about 2% of body weight, but more importantly, my blood tests have shown a drastic improvement in high-sensitive C-reactive protein (hsCRP), an inflammatory marker predicting the risk of cardiovascular diseases. This is not a surprise since inducing weight loss and prevention of cardiovascular diseases are some of the known benefits of intermittent fasting, which I have explored in one of my previous blog posts (See Fasting and Health). Less is known about the benefits of fasting in cancer treatment, but this is fast changing with the growing attention in research. This is good news for all cancer patients.

The science behind

Cancer cells (in purple) has a higher metabolic rate than the surrounding normal cells (in pink) [Source: NIH public domain]
Cancer cells are known to have a much higher metabolic rate than normal cells. They feed on glucose as the main fuel for growth. During fasting, the blood glucose level and the insulin growth factor concentrations are drastically reduced. Since some cancers have been found to express higher concentrations of insulin growth factor, fasting can thus potentially cause cancer cell death. Nonetheless, this mechanism has not been fully validated [1].

The reduction in insulin growth factor also prompted normal cells in the body to redirect energy toward a conservation mode with increased cell maintenance and repair and reduced growth and proliferation. This effect can help to reduce damage during chemotherapy and enhance immunity [2]. The enhanced immunity, in turn, can assist in the elimination of cancer cells and inhibit the growth of a tumour [3]. Additionally, fasting also brings about other cancer-protective mechanism, including reduced oxidative stress and inflammation as well as improved cytokine profile [4].

The evidence

Fasting has been shown to reduce side-effects of chemotherapy. [Image source: Flickr]
Studies have indicated that fasting can potentially benefit cancer treatment in many ways. A systematic review that covers a total of 22 studies, including 18 animal studies 4 preliminary experiments on humans published between 2002 to 2016 concluded that fasting can potentially reduce chemotherapy side-effects, suppress cancer progression, and improve survival [5].

Fasting has been found to be a safe and feasible therapy to combine with chemotherapy in a pilot trial [6]. In another study with 34 patients with gynaecological cancer, introducing a 60 h-fasting period during each round of chemotherapy cycle was found to be well tolerated and appears to improve QOL and fatigue during chemotherapy [7]. Similar findings were reported in an earlier trial with breast cancer patients as well [8].

In one observational study that analysed data from 2413 women with breast cancer found that by simply prolonging the length of the nightly fasting interval to more than 13 hours the risk of breast cancer recurrence and mortality is greatly reduced [9].


Short-term fasting can potentially improve the treatment outcomes and the health of cancer patients.  However, since some cancer patients may be at risk of developing malnutrition and muscle wasting due to extreme weight loss during cancer treatment, the practising fasting needs professional advice. For any cancer patient who wishes to try out fasting, it is best to discuss with a doctor practising integrative medicine or get assistance from a qualified naturopath or nutritionist who can help to devise a fasting program and monitor your nutritional status.

Get professional help to start your fasting regime!

Nonetheless, do not expect the oncologists to endorse fasting as a supporting strategy to treat cancer any time soon. Without evidence from large-scale randomised control trials, the medical establishment will continue to consider fasting to be a promising but unproven therapy at best, if not dismissing it as a quackery [1,10].


[1]        P. Cathcart, C. Craddock, J. Stebbing, Fasting: starving cancer, Lancet Oncol. 18 (2017) 431. doi:10.1016/S1470-2045(17)30196-1.

[2]        G. van Niekerk, S.M. Hattingh, A.-M. Engelbrecht, Enhanced Therapeutic Efficacy in Cancer Patients by Short-term Fasting: The Autophagy Connection, Front. Oncol. 6 (2016) 1–7. doi:10.3389/fonc.2016.00242.

[3]        P. et. al Sun, Fasting inhibits colorectal cancer growth by reducing M2 polarization of tumor-associated macrophages., Oncotarget. 8 (2017) 74649–74660. doi:10.18632/oncotarget.20301.

[4]        M.N. Harvie, T. Howell, Could Intermittent Energy Restriction and Intermittent Fasting Reduce Rates of Cancer in Obese, Overweight, and Normal-Weight Subjects? A Summary of Evidence, Adv. Nutr. An Int. Rev. J. 7 (2016) 690–705. doi:10.3945/an.115.011767.

[5]        L. Sun, Y.-J. Li, X. Yang, L. Gao, C. Yi, Effect of fasting therapy in chemotherapy-protection and tumorsuppression: a systematic review, Transl. Cancer Res. 6 (2017) 354–365. doi:10.21037/12654.

[6]        T.B. Dorff, S. Groshen, A. Garcia, M. Shah, D. Tsao-Wei, H. Pham, C.W. Cheng, S. Brandhorst, P. Cohen, M. Wei, V. Longo, D.I. Quinn, Safety and feasibility of fasting in combination with platinum-based chemotherapy, BMC Cancer. 16 (2016) 1–9. doi:10.1186/s12885-016-2370-6.

[7]        S. de Groot, M.P.G. Vreeswijk, M.J.P. Welters, G. Gravesteijn, J.J.W.A. Boei, A. Jochems, D. Houtsma, H. Putter, J.J.M. van der Hoeven, J.W.R. Nortier, H. Pijl, J.R. Kroep, The effects of short-term fasting on quality of life and tolerance to chemotherapy in patients with breast and ovarian cancer: a randomized cross-over pilot study, BMC Cancer. 15 (2015) 1–10. doi:10.1186/s12885-015-1663-5.

[8]        S. de Groot, M.P.G. Vreeswijk, M.J.P. Welters, G. Gravesteijn, J.J.W.A. Boei, A. Jochems, D. Houtsma, H. Putter, J.J.M. van der Hoeven, J.W.R. Nortier, H. Pijl, J.R. Kroep, The effects of short-term fasting on tolerance to (neo) adjuvant chemotherapy in HER2-negative breast cancer patients: a randomized pilot study., BMC Cancer. 15 (2015) 652. doi:10.1186/s12885-015-1663-5.

[9]        C.R. Marinac, S.H. Nelson, C.I. Breen, S.J. Hartman, L. Natarajan, J.P. Pierce, S.W. Flatt, D.D. Sears, R.E. Patterson, Prolonged Nightly Fasting and Breast Cancer Prognosis, JAMA Oncol. 2 (2016) 1049. doi:10.1001/jamaoncol.2016.0164.

[10]      R. Caccialanza, E. Cereda, F. De Lorenzo, G. Farina, P. Pedrazzoli, To fast , or not to fast before chemotherapy , that is the question, (2018) 10–13.

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