Fasting
What’s in a fast?
Anyone who takes cooking seriously will likely have a decent collection of knives in their kitchen. All of them have the same basic function: to cut food. But each knife is designed for a specific task – chopping, peeling, carving, dicing, etc.
In a way, fasting is similar. All fasting involves changing ones eating schedule to deprive the body of food for some limited amount of time.
But from that simple definition, the kinds of fasts practiced varies. Each has unique different characteristics and functions. Each is designed to produce unique results.
The (very brief) History
Fasting has been practiced for almost as long as humans have been eating. Our earliest hunter/gatherer ancestors fasted regularly, albeit not by choice. Scarcity forced them to go without. Later, many religions included fasting as a means to get closer to God, a practice that remains part of many religious rites today.
Fasting is part of an evolutionary process where our bodies learned to withstand periods without food with the best adapted able to survive the longest. This may have been the first benefit of fasting and may partially explain why religions see value in it. Getting closer to God may serve as a compelling reason to fast, but the real prize lies with the health benefits.
Beyond God – The Benefits of Fasting
These health benefits are the reason why so many people choose to fast today.
Though they might not know the word, those who fast are hoping to achieve “autophagy” a process where the body consumes broken down cellular components. The theory is that autophagy cleans up all kinds of junk in the cells, old, dead unusable stuff like damaged DNA, etc.
Fasting is the ultimate ketogenic diet. After enough time without food, the body naturally enters ketosis turning to its own fat stores for fuel. This helps create metabolic flexibility as we tap into different fuel sources to power different activities. That said, if you are already in ketosis prior to fasting (by eating a high fat, low carb diet), fasting becomes much easier to tolerate as hunger will be less of an issue since the body knows it can just turn to it’s own fat when there’s no carbs to burn (that’s the metabolic flexibility at work).
Which fast is right for me?
There are a few well-established approaches to fasting. The right one for you depends on your goals and objectives. Here’s a brief rundown of the most popular.
Intermittent fasting
Where you eat only within a specific time window, between the hours of noon and 8pm, for example and fast for the other 16 hours of the day. While some would argue that this is more “time restricted feeding” than fasting, the difference is a matter of semantics. Note that the feeding window could be smaller or bigger but typically is no more than 10 hours to achieve benefits, which in this case don’t involve “autophagy” but can improve digestion, regulate insulin production and even increase the diversity of the micro biome as noted in this study.
The 24 to 48-hour fast
Is exactly as it sounds. No food for one or two full days, water only. Most people are able to do this without any problems or complications. Some will include beverages such as herbal teas and even coffee (Dave Asprey aka the “Bulletproof” coffee guy, is a big proponent of drinking coffee during a fast). Since there are no real markers for “autophagy” (the cell cleaning as described earlier) there is debate as to whether it kicks in after 24 hrs or not. The consensus seems to be that 36 hrs. might be the minimum but no one really knows for sure.
Fasting mimicking diet
Popularized by Volter Longo, this type of fast involves taking in a small amount of calories of specific macronutrients throughout the day over a 5 day period. This approach has been shown to provide most of the benefits of a complete fast while not completely depriving you of food altogether. Because of this, you’re much more likely to to stick with this program.
Liquid fasts
Where you consume only juices or broths. Because they are quickly absorbed, the digestive system doesn’t have to work as hard to get nutrients into the body. This allows the digestive tract time to heal while the body is still absorbing vitamins, minerals, and other plant compounds or, in the case of bone broth - amino acids.
If you’ve ever heard of, or done a “juice cleanse”, it’s not so much what you’re taking in - in this case the juice, but rather what you’re not taking in and therefore giving the body and especially the digestive tract a rest and reset period.
Prolonged supervised fasting
A fast mostly taken on for weight loss, the duration is typically from 5 days to several weeks or even months. Dr. Jason Fung, who has written several books on the subject, says that this type of fast is a perfect weight loss solution. The general concept is that our bodies store fat for a reason - to use in times of need. But when there is no famine or food shortages, we just keep packing on the pounds for that rainy day that never comes.
Enter a controlled, medically induced famine and watch the pounds melt away! However, please note: It is absolutely crucial that a prolonged fast is undertaken with the supervision of an MD.
Remind me again why I should be fasting?
Depending on the duration, fasting for a day or more at a time can induce what’s called “autophagy” which is the body’s way of house cleaning. Who doesn’t want to clean their house every so often? Daily intermittent fasting has a lot of benefits as well from improved digestion, a more diverse micro biome, weight loss and it helps create metabolic flexibility so that the body becomes more adept at using either fat or glucose (carbs) for fuel and that in turn keeps us out of the typical “glucose dependent, must eat every 2-3 hrs or I get hangry” scenario.
