Intermittent (or short-term) fasting has been shown to have very strong anticancer properties, the new research on this topic is very convincing. It is also a very easy diet to follow.

The subject of diet is covered extensively in the book (Cancer: Improving Your Odds), including intermittent fasting. But this topic is important enough, and new research is coming out all the time, that I thought I would cover it again here. This is actually a two part article, there is a separate article on Intermittent Fasting (IF) on The Gut Health Protocol website where it discusses intermittent fasting and its benefits to gut health and the microbiome. If you’ve read Cancer: Improving Your Odds you know that gut health is very important to the immune system’s ability to fight cancer throughout the body.

We’ve known for many decades that calorie restriction (without starvation or nutrient deficiency) extends life, prevents and treats Type II Diabetes, improves / prevents several chronic health conditions, and can even help prevent (and adjuvantly treat cancer). In the past it was believed that this was just due to fewer calories consumed than expended over the course of a day. However, new research is showing that some diets can also mimic the benefits of calorie restriction restriction with no actual reduction of calories! The diet that is going to be discussed here is “intermittent fasting”.

Intermittent Fasting Described

You can find a lot of information on how to do Intermittent Fasting (IF) with a quick Google search, so I’m just going to cover the basics here. The concepts of intermittent fasting couldn’t be easier to understand; simply don’t eat for most of the day and squeeze all your calories into a few hours of the day.  This sound rough, but after you get use to it you’ll find that it is not only simple, but easy to implement and fairly painless.

There are various types of Intermittent Fasting:

Much of the research on health benefits involved a simple 16:8 or 18:6 diet, so nothing too extreme.  I personally fluctuate depending on my schedule, but I shoot for a minimum of a 16:8 diet, 6 days per week (often 7 days/week). My average fast is 17-18 hours, but every now and then I’ll take that up to a 20:4 or longer.

What makes this diet so easy is that you can simply eat what you want during the window where food is allowed. Though not optimal, even if you make up the calories from the skipped meal the fasting period is still beneficial! I’ve found the easiest way of intermittent fasting is to skip breakfast (yes, sleeping time counts as fasting).  I’ll eat lunch around noon, and dinner at 5-6pm; that means no food between 6pm and noon the next day (that is 18 hours!)  During my fasting period I drink decaff coffee and decaff herbal teas (including chaga tea as it has anticancer properties, and nettle tea to help with detoxifying), I also have water to sip on. When intermittent fasting I have more energy and focus, even towards the end of my fast, than I use to have eating 3 meals per day (and a snack here or there). Do I feel hungry?  Sometimes a little, but with the extra energy I really don’t notice it. The hot drinks also help.

Simple right?  Yes, but we’re talking cancer here. Since I’m a cancer survivor, and have already had a recurrence (before starting everything discussed in the book and this diet), I take the opportunity to optimize this way of eating for more anticancer benefits. Besides incorporating the foods discussed in Chapter 6, I also implement the Chapter 4 advice of largely avoiding  sugar and gratuitous carbohydrates (e.g. chips). Every now and then I go completely no carb during the eating period (though admittedly, not every day).  I would suggest that you become familiar with everything nutritionally that can help you (from reading Cancer: Improving Your Odds) and implement what you can, when you can. We are fighting cancer after-all. I still find this one of the easiest diets to follow and I’ve tried many; it is also one of the most beneficial, with new research coming out all the time.

I use a free app on my phone called “Zero-Fasting Tracker” it does all the math for you, click on Start Fast and it tells you when your 16 hours are up (if that is the fasting period you’ve selected as your default). It also tracks your daily progress and includes weekly articles on intermittent fasting.

Cancer Benefits

Studies on intermittent fasting (IF) have found that it both benefits standard cancer treatments and exerts its own benefits against cancer.

One of the most interesting benefits of IF is on its positive effects on the gut’s microbiome. These effects directly influence the body’s immune system in ways that help fight cancer throughout the body (also see Chapter 2).

“IF led to increased gut bacteria richness, enrichment of the Lactobacillaceae, Bacteroidaceae, and Prevotellaceae families and enhanced antioxidative microbial metabolic pathways. IF altered T cells in the gut with a reduction of IL-17 producing T cells and an increase in regulatory T cells… IF has potent immunomodulatory effects that are at least partially mediated by the gut microbiome.” — PubMed ID#29874567

One of the ways that IF attacks cancer is through greatly improving autophagy; this is where after our immune system identifies cancer cells it then consumes them (thus destroying them). Autophagy is also beneficial in attacking disease causing microorganisms, such as pathogenic bacteria and yeast, as well as cleaning up damaged and dead human cells.  (see below for a glossary of abbreviations found in these studies)

“Abundant and convincing preclinical evidence shows that STF (short-term fasting) can decrease toxicity and simultaneously increase efficacy of a wide variety of chemotherapeutic agents… Furthermore, it is potentially effective in a wide variety of tumors” (2019) — PubMed ID#PMC6530042

“dietary restriction (DR) has been shown to extend the lifespan and reduce the development of age-related diseases such as diabetes, cancer, and neurodegenerative and cardiovascular diseases… Recently, studies in in vitro and in vivo models have shown that intermittent fasting improved the chemotherapeutic response to cisplatin, doxorubicin, cyclophosphamide, oxaliplatin, sorafenib, mitoxantrone, gemcitabine, etoposide, temozolomide and tyrosine kinase inhibitors in models of glioma, neuroblastoma, melanoma, fibrosarcoma and breast cancer, colon cancer, pancreatic cancer, hepatocellular cancer and lung cancer. IF has also been shown to improve the radiosensitivity of glioma and breast cancer… Our group also demonstrated that nutritional deprivation enhanced the sensitivity of both wild type and BRAFV600E human melanoma cells” (2018) — PubMed ID#PMC6257056

“In cancer xenografts models, both TKIs (Tyrosine kinase inhibitors) and cycles of fasting slowed tumor growth, but, when combined, these interventions were significantly more effective than either type of treatment alone. In conclusion, cycles of fasting or of specifically designed fasting-mimicking diets should be evaluated in clinical studies as a means to potentiate the activity of TKIs in clinical use.” —  PubMed ID#PMC4494907

“Autophagy is sometimes referred to as cellular “cleansing”… Short-term fasting induces profound neuronal autophagy… sporadic fasting might represent a simple, safe and inexpensive means to promote this potentially therapeutic neuronal response… It is well known that food restriction induces autophagy in many organs and tissues… short-term food restriction induces a dramatic upregulation of autophagy in cortical and Purkinje neurons. To our knowledge, this is the first demonstration that food restriction leads to in vivo neuronal autophagy” — PubMed ID#PMC3106288

In this study they looked at 2413 women with early-stage breast cancer, but without diabetes. They also controlled for several factors, including total calories. This study did not look at longer 16-18 hour fasts, which other studies have shown to be even more beneficial. The take-away point here is clear, consuming any food late in the evening is a bad idea, and night time fasts of less than 13 hours are associated with breast cancer recurrence (and most likely contracting various cancers in the first place).

“a short nightly fasting duration (<13 hours per night) was associated with a 36% higher hazard for breast cancer recurrence… intermittent calorie restriction prevents mammary tumor development to a similar, or even greater, extent than chronic calorie restriction… Positive metabolic changes associated with intermittent fasting regimens include improved glucoregulation… longer nightly fasting duration… (was) associated with a significantly lower HbA1c level… compared with women whose HbA1c was less than 6.5%, the risk of all-cause mortality was twice as high in women whose HbA1c was 7.0% or more… a recent analysis of 2019 adult women in the National Health and Nutrition Examination Survey showed that a longer nightly fasting duration was associated with significantly lower CRP concentrations… Consuming food at abnormal times (eg, late at night) can result in misalignment of circadian rhythms, which can influence sleep patterns and disrupt metabolic factors, such as glucoregulation.” (2016) — PubMed ID#PMC4982776

Even if you consume the same number of calories intermittent fasting still shows benefits.

“Investigators compared time-restricted feeding (tRF) to AL access, both in a high-fat diet (HFD) in mice. They have seen that mice under tRF consume equivalent calories from HFD as those with AL access. However, the former is protected against obesity, hyperinsulinemia, hepatic steatosis, and inflammation and also, has improved motor coordination. Hence, they have concluded that a tRF regimen improved CREB, mTOR, and AMPK pathway functions and oscillations of the circadian clock.” — PubMed ID#PMC6036773

Besides autophagy, it is likely that intermittent fasting benefits cancer prevention and treatment through its effects on cellular glucose sensitivity and lower insulin levels. As outlined in the book, interventions such as calorie restriction, exercise, and certain diabetes drugs such as metformin all show anticancer benefits due to their effects on glucose sensitivity. This benefit is one of the most important reasons why I feel that daily time-restricted fasting is the preferred intermittent fasting method.

“studies in overweight and obese subjects have shown that IER can lead to greater improvements in insulin sensitivity (homeostasis model assessment) than can CER, with comparable reductions in adipokines and inflammatory markers” — PubMed ID#PMC4942870

Intermittent fasting also led to better Quality of Life (QOL) during chemotherapy and improved chemo tolerance.

“STF has been documented to induce profound changes in gene expression and cellular metabolism that render normal cells more resistant to oxidative stress and thus may confer benefit in the situation of cancer treatment by chemotherapy… STF led to a better tolerance to chemotherapy with less compromised QOL and reduced fatigue within the 8 days after chemotherapy… Our results confirm the feasibility and tolerability of STF accompanying chemotherapy and extend on these findings by indicating a potential beneficial effect on QOL, fatigue and well-being during cancer treatment.” — PubMed ID#PMC5921787

The following meta-analysis study was done on mice and other animals. But it shows that calorie restriction has huge benefits in preventing breast cancer.

“The pooled risk difference for the 14 studies was -0.55 with a narrow 95% confidence interval (-0.69; -0.41), implying that the energy-restricted animal groups developed 55% less mammary tumors than the control groups… This meta-analysis confirms that energy restriction in itself consistently protects against the development of mammary tumor in mice, irrespective of the type of restricted nutrient or other study characteristics.” — PubMed ID#12866038

“The average survival time of the tumor-bearing mice on the low-calorie rations was about 20 per cent longer than that of the full-fed controls. Furthermore, in two-thirds of the pairs the restricted mouse outlived its respective mate. The limitation of food intake also resulted in a decreased rate of growth of the tumors, reduced incidence of additional mammary carcinomas, and lower frequency of grossly visible metastases to the lungs.” — AACR Journals

“We found that CR reduces growth of mammary tumors and metastases, involving several different mechanisms, confirming and extending prior work on this topic… the literature abounds with studies showing that CR leads to a reduction in spontaneous and chemically induced tumors in rodent models… (CR) reported a reduction in the average number of metastatic nodules per lung… One major finding of our investigation was that CR not only reduced the primary tumor size but also the number and size of metastases… several mechanisms initiated by CR-mediating metastatic spread and growth are involved”  — PubMed ID#PMC3165123

Note: It should be pointed out that if you have cachexia (weight loss due to wasting) you will need to work with a nutritionist that specializes in cancer treatment. It will be important to maintain your daily calorie levels to prevent further weight loss. This can still be done while intermittently fasting.

If you have, or have had, cancer please consider giving intermittent fasting a try, especially with the other recommendations found in Cancer: Improving Your Odds. This what I do, and what I will continue to do. Even if you’ve never had cancer intermittent fasting has many health advantages and can improve energy and focus.

Intermittent Fasting – Gut Health Benefits