When people think of “fasting” what comes to mind is an almost-intolerable short period of time without food, and with nothing to drink (except maybe water) and where people usually spend most of the time counting until they can eat again. This is the case when we are used to burning carbs as our fuel source and then just stop eating. Our body slows its metabolism in response to the severe calorie restriction in an effort to spare energy. We feel cold, tired, lethargic and we find it difficult to concentrate because our body is in starvation mode.
When we are fat-adapted, we use the fat in our diet (dietary fat) and our own fat stores (endogenous fat) as our fuel source. When we “fast”, we stop supplying our body with dietary fat, so our body relies solely on our fat stores to supply its energy needs. Most of us who are following a low carb high fat diet have plenty of endogenous fat, so when we aren’t eating, we don’t feel hungry, tired or cold because our body has a plentiful source of energy! Our basal metabolism doesn’t drop. Rather than feeling cold and tired and finding it difficult to think, we are able to think clearly using ketones produced from fat to fuel our body, rather than glucose.
“Intermittent fasting” is simply increasing the amount of time between meals. Fasting is not eating or rather, not eating now. It’s different than “starving” because our basal metabolic rate is being maintained through our fat stores. When we are in starvation mode, our basal metabolism drops significantly in order to spare energy – that’s why we feel cold and tired, because our body is saving calories for our brain and our heart to function. Fasting also doesn’t mean that we can’t consume anything! There are plenty of things we can have during the delay before our next meal. The most natural “intermittent fast“ is the one between after supper and breakfast the next morning. Yes, that is why it is called “breakfast“.
When we eat, insulin is released in response to the presence of carbs in the food we eat and functions to (a) move glucose out of the blood and to (b) store the glucose that is not immediately needed for energy, as fat.
When we are accustomed (as most of us have been) to eating three meals a day plus having a couple of snacks, insulin is released every few hours. If we have been “grazing”, we have been constantly releasing insulin. As a result of this, our cells have become insensitive to insulin – something known as “insulin resistance“, or insulin tolerant. To conceptualize this, think of going into a room with loud music. At first your ears buzz and your auditory system is overwhelmed, but after a bit of time, your body adapts. It’s similar with smell. When you’re exposed to a pungent odor, at first that’s all your can concentrate on, but after time passes, your brain starts to “tune out” the signals from your nose and you become less aware of the smell. It’s not that the odor decreases, but our response to the odor, decreases as we become “tolerant” to that molecule bound to our olfactory receptors.
The difference with “insulin resistance” is that it is more than our body becoming “tolerant” of the circulating insulin, it actually responds less to it.
Think of someone that drinks considerable amounts of alcohol. They can have 3 or 4 drinks and not feel intoxicated, because they have a “high tolerance” to the ethanol in the drink. It takes more and more alcohol for them to respond. When someone is “insulin tolerant” (also called “insulin resistant“), the same amount of insulin has less and less effect, so to adapt, to be able to move the glucose out of the blood and store the excess energy as fat, the body needs to release more and more insulin. From years and years of eating 3 carb-based meals plus a couple of carb-laden snacks each day, our insulin levels simply don’t fall to baseline.
When someone is not insulin resistant, delaying the time before the next meal enables their insulin levels to fall to baseline (10-30 pMol) in approximately 12 hours, so if they don’t eat anything after dinner and their first meal of the day is breakfast the next morning, that time period is usually close to 12 hours. However, for people who are insulin resistant, a longer time period is often needed for their insulin levels to fall to baseline. Just as insulin resistance developed over time, gradually, a new lower baseline can be set over time by increasing the length of time that one intermittently fasts.
A twelve-hour fast is the easiest one for most people to do, because during most of it, they’re asleep!
This is the one I suggest to my clients once they’re fat-adapted (usually after ~4 weeks of eating low carb high fat) as all it entails is not eating anything after supper until breakfast the next morning.
So, say they finish dinner at 6:30 PM, then the next time they eat is breakfast the next morning at 6:30 AM. This simple, short 12-hour “fast” is just enough to enable their insulin to fall to baseline. Doing this often, if not daily is the goal. This is entirely do-able and an important first step in restoring insulin sensitivity and it is certainly not something “radical”. Years ago, people didn’t eat after supper!
People who have Type 2 Diabetes should check with their doctor before beginning doing any form of Intermittent Fasting – and definitely should do so if they are on any kind of medication to manage their blood sugar, blood pressure or cholesterol, without having their doctors oversee it. Medication will often need to be adjusted downward (and sometimes eventually discontinued entirely) as insulin sensitivity returns, so don’t do this without involving your doctor, first!
Eighteen Hour Fast
Once people have become used to not eating from supper until breakfast, they may want to wait to eat their first meal until noon the next day, especially if they don’t feel particularly hungry in the morning. Some people are not “breakfast” people and if they eat well the night before, they may not want to eat in the morning. An eighteen hour “fast” is from after someone has finished dinner (say, at 6:00 PM) until noon the next day.
Many do want their cup of coffee, which is totally fine provided it is unsweetened. I don’t recommend that people use sugar substitutes, especially the sugar alcohols such as sorbitol, mannitol or xylitol which have the same number of carbs per teaspoon as ordinary table sugar.
Cream can certainly be added to drip coffee and there’s no need to give up your morning latte or cappuccino – just a little creativity to replace the milk (which has almost as many carbs per cup as a slice of bread!).
My trick is to foam 1/2 an ounce of cream with an ounce or ounce and a half of cold, filtered water.
This makes fasting until lunch entirely possible!!
Twenty-four Hour Fast
Note: I don't do these and I don't recommend that my clients do these unless they are being very closely monitored by their doctor, however I want to describe them, so people know what they are.
A twenty-four hour “fast” is from the end of supper one day, until the start of supper the following day (technically it is a 23-hour fast unless you add the extra hour ). As with the eighteen-hour fast, one can have unsweetened coffee or tea with a drop of cream, club soda (seltzer) with a twist of lime or lemon, or “bone broth“. “Bone broth” can be made from any kind of meat, fish or poultry bones, but for me, when I think of “bone broth“, I think of a wonderful, rich broth made from beef marrow bones, that is gently simmered overnight on the stove, ready to be sipped as desired, on a fast day.
To avoid getting constipated, many people will take psillium fiber with water each morning and which can be added to cups of “bone broth” or dissolved in a little bit of diluted coconut milk.
What’s not to love about sipping this when “fasting”?
The main purpose of delaying the time between meals (“intermittent fasting”) is to restore insulin sensitivity. When we aren’t eating, we aren’t releasing insulin – and as we continue eating low carb high fat and delaying the time between meals, our insulin receptors become sensitive to insulin once again.
Normalized blood sugar levels (both fasting blood glucose and HbA1C) is a natural byproduct, not the goal. The goal is releasing less and less insulin in response to the food we eat and our body’s sensitivity to the insulin that we do release, being restored.
Weight loss is another added benefit!
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Note: Everyone's results following a LCHF lifestyle will differ as there is no one-size-fits-all approach and everybody's nutritional needs and health status is different. If you want to adopt this kind of lifestyle, please discuss it with your doctor, first.
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