Updated: Sep 3, 2020
I’m often asked whether one should try intermittent fasting. First I explain that “Intermittent Fasting” can mean different things — in its most basic form, it’s not eating from 12 or more hours each day. From there, the number of hours one might fast yield different results. For instance:
12 Hour Fast (e.g., 8pm to 8am)
- Safe for most people
- Supports digestion by allowing the GI system enough time to move food through
- Supports migrating motor complex — meaning, it helps the GI system move and helps prevent bloating and constipation
- Supports detoxification (because of all of the above)
14 Hour Fast (e.g., 8pm to 10am)
- Safe for most people — see below for exceptions
- Now, many people will start to enter a state of ketosis, or burning fat for fuel in place of glucose. This is a topic all its own but it's like burning cleaner fuel
- All of the benefits of the 12-hour fast plus:
- Increased mental clarity and focus (ketones fuel the brain)
- Supports fat burning and can help with weight loss
16-18 Hour Fast (e.g., 8pm to 12pm or 2pm)
- More intense — not right for everyone, see below for examples
- In addition to being in ketosis, some say the process of autophagy kicks in here — though sources disagree, with many saying it can take 24 hours or even several days (must be done under medical supervision) to activate autophagy.
24+ Hour Fasts — should be done under professional guidance
- Autophagy and enhanced stem cell production after re-feeding
“Auto” meaning self, “phagy” meaning eating (remember phagocytosis from high school bio, where white blood cells engulf and destroy pathogens?) — basically the process of recycling and removing damaged parts of cells, including proteins that have become dysfunctional, damaged DNA, and other cellular debris. It also leads to the activation and proliferation of stem cells. In a nutshell, it keeps our cells fresh, which is why it’s thought to play a role in healthy aging and cancer prevention.
Common questions and cautions around IF:
Won’t I lose muscle?
If done properly, you’ll maintain muscle and burn fat, which is why a lot of people like IF for weight loss. The key is to be sure to nourish yourself adequately during the feeding window.
What breaks a fast?
It depends on who you ask. I believe that anything other than water, black coffee and tea breaks a fast. Anything with calories. That includes any sort of milk or sugar in your coffee (though stevia would be OK). Some people love Bulletproof-style coffee in the morning with fat (coconut oil, MCT oil, butter, ghee) added to their coffee. While this will keep you in ketosis (fat burning) mode, there is debate about whether it allows for some of the other physiological benefits of fasting.
What’s Circadian Fasting?
There’s a new (old) idea circulating about eating only when it’s light out. This makes sense to me from an evolutionary standpoint and is something I’ll be experimenting with to see if it benefits my sleep/wake cycle.
What about intuitive eating?
I often coach my clients to eat when they’re hungry, not just because it’s time to eat. If you pay attention, I bet you’ll find that you’re not actually hungry for several more hours that you’d normally wait some days.
- If you can’t fast comfortably without caffeine, IF might not be right for you. Coffee or other caffeine will suppress your appetite but it may come back to bite you later in the day in the form of increased hunger and sugar cravings.
- IF has many of its benefits BECAUSE it’s viewed as a stress on the body — while many people can tolerate that and reap the benefits, anyone who’s trying to heal and reduce stress might hold off until they’ve done some foundational healing work. Anyone with adrenal fatigue, chronic fatigue, women who are pregnant or looking to get pregnant, women who are nursing — basically anyone that needs their body to feel as safe and nourished as possible may not want to try IF just yet.
If you’re not sure whether IF is right for you, consider working with a nutritionist or health coach who understands it. I offer a free discovery session — learn more.