I recently completed a 4-day water fast and felt great doing it! I have been practicing fasting of greater than 24-hours periodically for over 3 years. Even though it sounds daunting and crazy at first, it is actually easier than you think, and research very clearly shows that it has many benefits to health and longevity. There is a lot of information (and misinformation) out there on fasting, so I thought a short post would help introduce people to the concept.
What is Fasting?
Fasting is the activity of abstaining from any caloric food or drink. Fasting has been a part of religious practices for over a thousand years. Our bodies have evolved to go without food for long periods, but modern food availability has made this much less common. All the research I have read shows that periodic fasting has many benefits for a healthy body.
There are many different protocols for fasting, but typically water, black coffee or tea are allowed, but no calories. In this post I am specifically covering the topic of fasting GREATER THAN 24 HOURS. Time Restricted Eating (commonly referred to as Intermittent Fasting) is something very different. In my opinion, the benefits of Intermittent Fasting have been greatly over-stated. Many "experts" use benefits from fasting beyond 24 hours and incorrectly apply them to eating in 16-8 or 18-6 hour eating windows. Using such restrictive eating windows can help people consume less calories, but the benefits beyond that are typically overblown. I will discuss eating windows in a separate post, but this post focusing on the benefits of fasting of greater than 24 hours. During a long term fast the body goes into a deep state of ketosis, which has unique benefits. Now I don't think staying in ketosis long term is optimal, but our bodies are designed to periodically go without food for long periods and enter deep ketosis occasionally. Keto will be covered in depth in a separate post as well.
Why I Fast:
Fasting for me has become more of a ritualistic tool that I believe plays a key part in maximizing longevity. While fasting for 2-5 days and beyond can seem absolutely impossible at first, it's actually quite empowering and helps me achieve a feeling of a "reset". In addition to the many health benefits of reducing risk of multiple chronic disease states, it has also contributed to me really gaining control over my hunger. I do it for the health benefits, not as a calorie-cutting weight loss tool. I view it as a periodic cellular cleanup, a deep clean of dysfunctional cells and short term stress on the body that results in a strengthening hormetic response. These beneficial hormetic responses are discussed below.
How I Fast:
About once per month I aim to do a fast of 36 to 48 hours. About twice per year I will go for a longer fast of 2-5 days. On a daily basis I don't usually eat in such a restrictive time window. My daily eating window varies and is usually mostly determined by my exercise type and timing.
Benefits of Fasting:
The benefits and cellular functions that I mention below are very complex and nuanced process. I present them here as very simplified definitions and I would be happy to expand upon them in future posts or discussion (just let me know in the comments). Again, these benefits apply to long term fasting, not intermittent fasting or time restricted eating.
- Reduction In Cancer Risk
- Autophagy - defined as the process of your body breaking down dysfunctional older cells and reusing their cellular components to maintain healthy cells. Cancer originates from dysfunctional cells and this process of autophagy helps "thin the herd" so to speak.
- Ketosis & Cancer - cancer cells prefer to use glucose as their main fuel source. During a fasted state your body is using almost exclusively ketones (made from your fat stores) and thereby contributes to this process of "thinning the herd" by starving the cancer cells.
- Reduction in Alzheimer's Risk (and all Neurocognitive Diseases)
- BDNF - Brain Derived Neurotrophic Factor - often referred to as the Miracle Grow for your brain. Fasting is one of the best ways to boost BDNF (exercise is another great way). BDNF stimulates the repair and regrowth of neurons (brain cells).
- Ketosis & The Brain - Under normal conditions the brain primarily relies on glucose as its main energy source. However, an important characteristic of neurocognitive decline is that the brain's ability to properly utilize glucose as a fuel source also declines. This is why it's often referred to as "Type 3 Diabetes". In these cases the brain is able to utilize the ketones for energy more efficiently during the fast. The fasting process also helps improve insulin sensitivity in the brain, helping glucose metabolism improve long term.
- Reduction in Diabetes Risk (Type 2)
- Insulin Sensitivity - one great benefit of fasting is that it can improve insulin sensitivity throughout the body. This helps your body better balance and manage blood sugar levels which is the. Type 2 Diabetes is defined as the inability of your body to properly maintain balanced blood sugar levels. Diabetes increases your risk for almost all other chronic diseases, so by increasing insulin sensitivity, your are reducing your risk of all major chronic health conditions.
- Improve Digestive Health
- Microbiome - your degestive microbiome consists of bacteria in your colon. A healthy balance microbiome is key for not only digestive health, but also contributes to healthy systems throughout the entire body. Fasting helps starve out the less beneficial bacteria in the colon, while the more beneficial bacteria are able to survive by feeding off of the mucosa of the colon.
- Giving it a Rest - One way I look at fasting is that it helps give your digestive system a break. It's almost impossible to completely avoid some of the highly processed foods in our diet, which break down our digestive system. During this break of fasting, the digestive system can focus on repairing and rebuilding some degradation caused by some of the burdensome foods we eat.
- Fat Loss
- Burning Fat - Obviously if you're not eating for greater than 24 hours you are going to burn some fat. Depending on your activity level, you could burn about a pound of fat/day of fasting. However, this is not the main reason I fast.
I hope this post was interesting and helpful to many of you! If you have never fasted it can seem overwhelming, but if you have questions please feel free to comment below, or contact me for support & guidance!
Resources:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6314618/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7699472/
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