For those of you who have been following Molly and me for any length of time, you are probably aware of our fondness for utilizing intermittent fasting (IF) as a powerful and effective tool to optimize health and longevity. There are many forms and practices of intermittent fasting, such as alternate day fasting, 5:2 fasting, periodic fasting (which involves multiple days of consecutive fasting) as well as time restricted feeding (and various others).
The health benefits of fasting are well-established and backed by research and more and more benefits are being uncovered in the scientific community as this is a hot topic with ongoing research trials and researchers, scientists and physicians dedicating almost, if not all, their entire professional careers to researching fasting utilizing different protocols, mice and human trials, etc.
For the purpose of this post, I want to focus a bit on Time Restricted Feeding (TRF for short).
TRF is simply a set period of time when you eat (eating window) and a set period of time when you fast (no eating or drinking anything with calories). In my expert opinion, TRF is the easiest and most sustainable IF practice and the method I recommend for most people.
Ideally, some sort of TRF is practiced on a day-to-day basis so the fasting benefits can be achieved daily. How long to “fast” on a day-to-day basis is definitely an individual thing that will vary from person to person and, oftentimes, from day-to-day or season-to-season, depending on what life throws at you.
So, when and how long should you fast?
As I mentioned above, fasting length will vary from person to person based on several factors including (but not limited to): overall health, body composition, hormone variations, metabolism, degree of stress, sleeping habits, work shift, carb “dependency”, ability to burn body fat for energy and many more.
Circadian Rhythm Consideration:
It’s important to schedule fasts around our innate circadian rhythm to maximize health benefits and minimize damage done from eating at the “wrong” times. For many years, the so called “experts” have preached the “calorie in, calorie out” myth of weight maintenance saying it doesn’t matter where the calories come from or what time you eat them, it’s all the same. I respectfully disagree with this hypothesis. I’m not going to get into the “calorie in, calorie out” argument in this blog post, but I do want to touch on the topic of aligning our eating with our circadian rhythm. The (very) basic premise of this is if we eat too late into the evening we disrupt our natural circadian rhythm and sleep cycles, thus interfering with all the health benefits we get when we sleep and, for added insult, potentially creating more harm than good and putting oneself at a higher risk for a host of health problems and bigger waistline. (For more info on this read up on Dr. Satchin Panda and The Circadian Code). Basically, instead of our bodies repairing and regenerating while we sleep it is focused on digesting and processing food if we eat too soon before bedtime.
So, what this means in basic terms and recommendations is to STOP eating and start your fast at least 2-3 hours before you go to bed to allow for digestion and normalization of blood sugar levels prior to falling asleep. It is NOT recommended to eat a snack at 11:00 PM and then hit the sack a little while later due to the potential alterations of your natural circadian rhythm and interruption of the multiple beneficial processes that take place while sleeping.
So, again, how long should you fast?
After stopping eating in the evening, say 2-3 hours before bedtime, let’s assume you get the recommended 7-8 hours of sleep. By the time you wake up, you are have already fasted at least 9 and as many as 11 hours! Now, depending on your fasting goal for the day, you are probably through the bulk of the fast. How long should you fast? As I alluded to above, this is definitely an individual thing due to a variety of factors. A popular practice is the “16:8” method of time restricted feeding. This means you fast for 16 hours and have an 8-hour eating window. For example, you start fasting at 7 pm, go the bed, wake up and continue fasting until 11 am (16 hours), which leaves 8 hours for your feeding window: 11 am to 7 pm. This can be great for many people, but not all people. Some people might do better on a 14:10 or 12:12 schedule, or some might do a mix of varying degrees of time restricted feeding. After some trial and error, I have figured out what works best for me (which may or may not work for you) and on most days I fast 12-13, sometimes 14 hours, with a 10-12 hour feeding window. On occasion I will go 16-18 hours fasting, and, every once in a while, I will throw in a 20-24 hour fast. Most of the researchers and fasting experts believe that 12 hours is the minimum time needed to fast to gain the positive benefits, and I would tend to agree with this. So, the answer to how long should you fast? I don’t know! That is something only you can figure out over time. The length of your fasts likely will (and should vary), and will change depending on life circumstances.
I hope you found this post informative and, more so, I hope you consider incorporating time-restricted feeding into your lifestyle to be used as a tool to help you on your path to healthy living.
Thanks for reading!