While the following information is, I think, still important to know, make sure to check out my more-recent blog (posted on 8/10/19) that includes updated science on how there may be risks inherent to fasting. You can find it here.
If I had my way, I would change the description of “Intermittent Fasting” that is associated with a Ketogenic way of eating to something like “Meal Timing.” Why? Because that’s all intermittent fasting is: timing your meals in a way that prevents a continuous spike in blood sugar and insulin.
Why Would Someone Fast?
For centuries people have been fasting. It is a common custom in Christian, Muslim, Hindu, Buddhist, and Jewish traditions. We, like animals, also tend to not want to eat when we’re sick. So, it’s not a new idea. It can be done for spiritual cleansing. It can also be done for physical cleansing. (More about why I fast here.)
The challenge with our current model of eating is that we eat ALL THE TIME! In fact, the average eating episodes a day in our country has increased to 10.5 (Fung, 2019)! I mean, think about it. We are told that it’s “better” for our health to eat frequent meals and snack during the day (which has no foundation in any research at all, by the way). After you eat a meal, notice how soon after you feel the need to snack. Once I started noticing how often I reached for a snack just to satisfy an emotional craving, I began to realize just how much of a problem this is!
So, What Do We Do?
Each time we eat something, our blood sugar (i.e. glucose) increases. Insulin is then released to sweep the excess sugar out of our bloodstream. So, how do we better stabilize blood sugar and reduce the amount of spikes during the day? Simple: stop eating.
Fasting is not starvation. If you are hungry or don’t feel good when fasting, the answer is also simple: eat. But, the whole point is to simply time meals so that you are minimizing the number of spikes in blood sugar during the day. When we minimize spikes, we improve our resistance (i.e. sensitivity) to Insulin (a good thing!).
So, start counting. Here’s the structure: You are either “feeding” or you are “fasting.”
The most common fasting durations are as follows:
- 12:12 – 12 feeding hours followed by 12 hours of fasting
- 16:8 – 8 feeding hours followed by 16 fasting hours
- 18:6 – 6 feeding hours followed by 19 fasting hours
- 20:4 – 4 feeding hours followed by 20 fasting hours
- 24 hour fasts
- 36 hour fasts
- Extended medical fasts (several Keto advocates, like Maria Emmerich, advocate for a monthly or yearly 3-7 day fast to keep on top of cellular health)
To be clear, not everyone on keto fasts. But, when your body runs itself off it’s own fat, it’s easy to use fasting as a tool to advance health using the natural tendency of the body to complete a cellular cleanse, done via two processes called “apoptosis” and “autophagy”.
Don’t Complicate It!
Fasting isn’t about pushing through hunger. When people are following a ketogenic/low-carb way of eating, the roller coaster of carb-dependence is not a factor so people are rarely hungry. (Remember, your body is feasting off it’s own body fat when it needs to!). Instead, fasting is about timing. And, any time you are not eating, even when you are sleeping, is considered “fasting” time.
Here’s an example: If you eat lunch at noon and finish a sit-down dinner (you are making time for a sit-down dinner, right?) with your family at home at 6pm; not eating lunch until the following day, you just completed a 18:6 fast. Surprise!
Here’s another example, let’s say you eat breakfast (although most keto-ers don’t feel they need to) at 8am. Even if you eat lunch and dinner, finishing eating at 8pm, and don’t eat anything after dinner until you eat breakfast at 8am the next day, surprise again! You just completed a 12:12 fast! Research shows that even daily 12:12 fasts can greatly reduce the risk of cancer given that you are giving your body time to heal via not constantly feeding it.
At it’s core: intermittent fasting is ancestral. Our paleolithic ancestors could not simply grab a granola bar every time they were hungry or at random times throughout the day. They had to balance their eating and resting windows to survive. And, if that schedule allowed us to survive and thrive for thousands of years, isn’t it something we should consider?
Why I Wrote This Blog
I am not a doctor. And, there are certainly things that prevent fasting from being appropriate for certain people (e.g. an eating disorder, hypoglycemia). But, fasting is also about intuitive eating. When my reactive hypoglycemia was severe, I couldn’t fast. It would have been dangerous for me. But, now that I am no longer a slave to food given that my blood sugar is stable with keto, I can practice intuitive eating and ask myself “Am I really hungry?” If I am, I eat. If I’m not, I don’t. Simple as that.
As I say repeatedly within this website: don’t take my word for it! The leading expert on the topic, Dr. Jason Fung, wrote two wonderful books that explain the science behind intermittent fasting: The Obesity Code and The Complete Guide to Fasting. Both completely changed my life and I trust could change yours, too!
Reference:
Fung, Jason. 2019.Intermittent Fasting [Powerpoint slides]. Retrieved from Nutrition Network Training, “Module 1: Scientific and Evolutionary Evidence”.
