Fasting has always had an important role in history. For centuries, people have practiced fasting for religious and ethical reasons, even as a powerful form of political protest.
Medical fasting has been around since at least the 5th century BCE when Hippocrates recommended fasting for patients who exhibited certain symptoms of illness. Fast forward a few hundred years, and abstaining from food and drink for sustained periods of time has once again come back in fashion; this time through a dietary practice known as intermittent fasting.
Intermittent fasting can cause changes in the body’s energy metabolism processes, improve overall health, and affect the progression of many diseases, particularly for cancer patients.
Available data shows that intermittent fasting holds the potential to:
1. Improve the effectiveness of chemotherapy
2. Decrease chemotherapy-related side effects
3. Improve the quality of life and daily function while on treatment
How is Intermittent Fasting Done?
Unlike most diets, intermittent fasting is not about a strict, restrictive set of foods; rather, it focuses on the timing of when food is consumed. It is a lifestyle adjustment with clear lines of when to eat and when to abstain completely. There is no slippery slope that starts with maybe a handful of popcorn during the movie and ends with a full-on midnight feast. Rather, at a certain time, or a certain day, the proverbial kitchen is simply closed.
Most commonly, intermittent fasting is done either by picking a daily approach, where part of the day is spent eating (usually between 6-8 hours) and the rest of the day (16-18 hours) is spent fasting, or a weekly approach, where, for example, two full days of the week are fast days.
The truth is our bodies are naturally primed to be on an eating/fasting schedule. There’s a reason our first meal of the day is called breakfast. We are, quite literally, breaking the fast we have been in while we are asleep. The problem is we are no longer going to sleep when it gets dark and wake up with the sun. And most of us aren’t working in the fields burning up all the calories we eat during the day. We are, on average, less active than we once were. We are staying up later than ever before; usually watching tv, scrolling through social media, or otherwise engaging in mindless activities after a long, hard day. And with these late-night activities often comes late-night snacking.
How Does Intermittent Fasting Work on the Body?
Briefly, when your body eats food it releases insulin which causes your liver, muscles, and fat cells to store glucose. When the glucose levels drop while in a fasting state, there is a decrease in insulin production, signaling your body to start burning stored energy. After 12 hours of fasting, having run out of stored energy, the body starts burning fat reserves.
What Does the Research Say About Fasting and Cancer
There are now studies suggesting a connection between intermittent fasting and cancer treatment. We have long since known that certain foods and diets can help with the prevention and treatment of cancer, but all too often, food plans are not necessarily included in the treatment of cancer patients. Numerous animal studies emphasize the benefits of combining fasting with commonly used chemotherapies, although there are only a few clinical trials done on cancer patients undergoing chemotherapy. In one such trial, the researchers assessed fasting while undergoing chemotherapy for 34 patients with breast or ovarian cancer. The fasting consisted of a restricted daily caloric intake of (< 400 kcal) primarily stemming from vegetable juice and light vegetable broth, starting 36–48 hours before the beginning of chemotherapy and lasting until 24 hours after the end of chemotherapy. It was found that this diet prevented the chemotherapy-related reduction in quality of life, and reduced fatigue.
Here are also some key findings from preclinical (animal) research:
Intermittent Fasting and Breast Cancer:
- Water-only fasting cycles (lasting 48–72 h) can be as effective as chemotherapy in reducing the progression of breast cancer
- Combination of fasting with chemotherapy – improves treatment efficacy
Pancreatic Cancer – Fasting combined with gemcitabine decreased pancreatic tumor progression by ~40%
Mesothelioma – Cisplatin, in combination with fasting, reduced mesothelioma progression by 60% compared to the control.
Glioma – Forty-eight hours of water-only fasting sensitizes mouse glioma models to radio- and chemotherapy.
Metastatic Neuroblastoma – 48 hours of water-only fasting followed by the single administration of a high-dose chemotherapy cocktail (doxorubicin and cisplatin) successfully reduces drug toxicity and metastases and results in long-term cancer-free survival
What are the Risks of Fasting?
It is important to note that intermittent fasting is not without its risks. Some patients need to be cautious. Especially:
- Patients suffering from malnutrition or cachexia
- For patients with chronic illnesses such as diabetes, fasting may not be appropriate.
- Patients with a history of eating disorders such as anorexia and bulimia should not fast.
- Patients should be cautious not to eat too much on non-fasting days/hours as this could counteract some of the health benefits of intermittent fasting.