Fasting and Cancer: Has Nature Provided a Treatment All Along?

Written by Dr. Colin Champ
Posted September 11, 2015

As a radiation oncologist, my research generally involves studying ways to make radiation therapy work better to kill cancer cells with fewer side effects. Oftentimes, this includes reducing the dose or potentially eliminating radiation therapy or other treatments altogether. However, as a promoter of natural health, including a healthy diet and high activity levels, I am constantly studying ways to kill and stop cancer cells through lifestyle alone (both personally and professionally). One of these methods is dietary fasting.

Humans have been fasting throughout most of their existence on this planet. Nowadays, for most Americans fasting consists of the grueling 3-4 hours in-between their bowl of “heart healthy” breakfast cereal or a muffin and their sandwich for lunch. This was not the case in our not-very-distant past. Back then, good old-fashioned fasting likely consisted of a lack of food for a large portion of the day or even several days — fasting from breakfast to lunch was a walk in the park.

Fasting to fight cancer?

Fast-forwarding several hundred centuries, a recent hot topic has been one of trying to discover methods to “starve” cancer cells, whether through carbohydrate restriction,1 calorie restriction,2 a ketogenic diet,3 or fasting,4 as has been discussed in the recent study entitled Fasting Enhances the Response of Glioma to Chemo- and Radiotherapy.

In this study, the authors attempt to increase our ability to kill glioma cells, the pesky brain tumors that are exquisitely resistant to most treatments, including chemotherapy, radiation therapy, and surgery. They also appear to have microscopic tentacle-like extensions and therefore are difficult to resect surgically, as the process of uprooting these tentacles would take out precious brain tissue as well. Thus, a method to help treat these pests is desperately needed.

After millions of years it appears that nature may have been providing us with this treatment, we just never knew it. In their study, Safdie and Brandhorst tested the effects of “starving” both cancer cells and normal cells without food for 48 hours. This was no modern-day fast (at least for us Americans) and it was performed in the face of chemotherapy and radiotherapy, which may be a daunting task for most cancer patients.

What they found was that the fast-sensitized mouse, rat, and human glioma cells to the treatment with chemoradiation, i.e. it resulted in significant killing of the cancer cells. They also found a significant decrease in blood sugar and IGF-1 in these animals during the fast and suggested that this may have played a large role, as we have discussed before here and here.

An interesting twist to their findings is the fact that while fasting may sensitize the bad guys to treatment, it appears to spare our good cells from much of the toxicity of chemotherapy and radiation therapy. Other words, when they decreased the amount of available sugar available to cancer cells, cell death significantly occurred in these cells with no change in the normal cells exposed to chemotherapy. The fasted mice also experienced delayed tumor progression and lived significantly longer. Not a bad result from simply removing food for a couple days.

We published similar data from my last institution showing that, for mice who have breast cancer and undergo nutrient restriction (overall or alternate day fasting), radiation therapy works significantly better to slow tumor growth and downregulate vital cancer pathways.5 A review of the available data further points toward carbohydrate restriction.1 If fasting is too difficult for cancer patients, perhaps simply removing carbohydrates may be an easier dietary change.

cancer chart

Figure: Alternate day fasts work as well as a single dose of 8 Gy (gray: a unit of measurement for absorbed radiation) of irradiation to slow tumor growth. However, when fasting occurs during radiation therapy, tumor kill is significantly enhanced. Figure from Saleh et al. Cell Cycle 2013.5

Treating and fighting cancer

Like many cancer studies, if it helps chemotherapy or radiation therapy to kill cancer cells, it likely helps those of us without cancer to ward it off. Fasting is no different. Some have even recommended alternate daily fasts for health benefit,8 though that may be somewhat difficult to get most of us to follow (including me).

So what do I do?

Alternate daily fasts would leave me unbearable to be around during the work week, as I am constantly running around my department seeing patients, treating patients, and checking films. Every time I try an extended fast during a work day I end up running ragged. Though, I am still able to fast from dinner until the following lunch (14-16 hours) during my research days when I see fewer patients.

In my opinion, the easiest and favorite time to fast is on the weekends. Most Saturdays and Sundays I do not eat until lunch starting at the dinner before. I do drink a cup of coffee in the morning and usually follow this with some sort of physical activity, or if it is 12 degrees in January in Pittsburgh, I walk on the treadmill while reading a book or listening to a podcast. These types of fasts are quite easy and enjoyable, and leave me with a great feeling of accomplishment on the weekends.

What kind of fast will work for you? There is only one way to find out...

To Your Health,

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Dr. Colin Champ is a practicing radiation oncologist and nutritional expert. He is the author of Misguided Medicine: The truth behind ill-advised medical recommendations and how to take health back into your hands” You can hear more from him as the host of the incredibly popular Caveman Doctor podcast.


1. Klement, R. J. & Champ, C. E. Calories, carbohydrates, and cancer therapy with radiation: exploiting the five R’s through dietary manipulation. Cancer Metastasis Rev. 1–13 (2014). doi:10.1007/s10555-014-9495-3

2. Simone, B. A. et al. Selectively starving cancer cells through dietary manipulation: methods and clinical implications. Futur. Oncol. 9, 959–976 (2013).

3. Champ, C. E. et al. Targeting metabolism with a ketogenic diet during the treatment of glioblastoma multiforme. J. Neurooncol. 117, 125–31 (2014).

4. Safdie, F. et al. Fasting enhances the response of glioma to chemo- and radiotherapy. PLoS One 7, e44603 (2012).

5. Saleh, A. D. et al. Caloric restriction augments radiation efficacy in breast cancer. Cell cycle Georg. Tex 12, 1955–1963 (2013).

6. Jirillo, A., Vascon, F. & Giacobbo, M. Bevacizumab in advanced cancer, too much or too little? Ann. Oncol. 19, 1817–8 (2008).

7. Gilbert, M. R. et al. A Randomized Trial of Bevacizumab for Newly Diagnosed Glioblastoma. N. Engl. J. Med. 370, 699–708 (2014).

8. Varady, K. A. & Hellerstein, M. K. Alternate-day fasting and chronic disease prevention: a review of human and animal trials. Am J Clin Nutr 86, 7–13 (2007).


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