2 weeks ago
The Big Idea
The ketogenic diet and fasting go together like bread and butter – or more aptly put, butter and butter. This is because successful fasts are dependent on ketosis: the ability to burn fat for fuel. And that ability is significantly increased while on the ketogenic diet.
Where you would normally take a few days to reach ketosis in a fast – and have to deal with fatigue and headaches until then – the adaptation process happens much faster when your body is already primed to metabolize fat instead of carbs. For this reason, ketogenic dieters often cycle in and out of fasting to take advantage of their fat-burning potential and to lose unwanted pounds.
People also use high-fat drinks (like Bulletproof coffee) to extend their ketogenic fasting windows. – Consuming high-fat coffee or tea in the morning keeps you feeling full for hours without the large insulin spikes or high doses of protein that would cancel out the benefits of fasting. There are even ‘fat fasting’ protocols that restrict calories to around half of normal, and limit them almost entirely to fat.
What it is
Ketogenic fasting is a long-term strategy that combines keto dieting principles (low carb, high fat) with routine periods of fasting for enhanced fat loss. These fasting periods can be intermittent – i.e. fasting for 16 hours per day or more, — or they can be prolonged fasts between one and five days.
But no matter the fasting duration, ketogenic fasts are always followed up with high volumes of fat and minimal carbs for normal eating. This helps a faster to stay ‘fat adapted’, which makes their fasting periods more effective and enjoyable.
(Make the bulleted part an indented, ‘Fast Facts’ kind of subsection.)
- Ketogenic fasting can be intermittent fasting, time-restricted eating, or prolonged fasting.
- High-fat drinks such as bulletproof coffee are often used in ketogenic fasting as meal replacements. These help to increase satiety and extend the fasting window.
Ketogenic fasting can also refer to the practice of fat fasting, which is subsisting almost entirely on fat for 1-5 days. This is done to speed up the process of ketosis for keto-diet beginners and to help keto dieters break through weight-loss plateaus of two weeks or longer.
Standard fasting, though proven effective for everything from weight loss to metabolic syndrome, can be very difficult for beginners. Ketogenic fasting solves the hunger problem by allowing high-fat beverages in the morning that can help a faster stick with their eating window. Going for longer periods without food is also easier when your body is fat-adapted through the ketogenic diet.
Ketones (aka ketone bodies) are proven to be therapeutic for brain disorders such as Alzheimer’s, epilepsy, and Parkinson’s disease. Fasting alone boosts ketone body production, but ketogenic diets increase ketones more over longer periods of time. When both methods are combined in ketogenic fasting, the brain-protecting effect is only amplified.
Lowers insulin levels
Many fasting benefits – including diabetes prevention and longevity – are linked to reduced insulin levels. (Insulin production essentially halts when you’re not eating.) The great thing about ketogenic fasting is that insulin levels are lowered that much more when your eating windows are almost entirely devoid of the carbohydrate-containing foods that spike insulin.
Though there isn’t much research related to ketogenic fasting, there is plenty of evidence showing how ketogenic diets and standard fasting are two of the most reliable fat-loss methods known to man. That said, there are tens of thousands of people who attribute weight losses of 30-100lbs and more to fasting on ketogenic diets – ketogenic fasting.
Most people automatically assume that more fat, especially more saturated fat like butter and coconut oil, would mean a greater risk of heart disease and atherosclerosis. But that’s wrong. In reality, higher levels of insulin (more carbs) are associated with the very diseases we’ve attributed to fat and cholesterol.
That said, there are low-level risks associated with ketogenic fasting:
- dehydration – much of the weight loss in the first two weeks is water loss
- diarrhea – high-fat diets can cause GI symptoms until adaptation occurs
- exacerbated liver and gallbladder issues
- electrolyte imbalance
It’s important to consult your doctor before making any significant dietary changes or before starting a ketogenic fasting protocol.
How to Do it
In order to start your own ketogenic fasting regimen, you’ll need to begin a ketogenic diet, then start an intermittent fasting schedule. Fat fasts are optional.
Starting a keto diet
To start a keto diet, you’ll need to do a lot of self-education to understand the types of foods you can eat, the foods you can’t eat, and what to expect in your first days and weeks of eating a high-fat, low-carb diet. You’ll also need to calculate the macronutrient levels (fat/protein/carbs) that will help you reach and sustain ketosis. This will vary from 10 grams of carbs per day for obese and sedentary people to 100 + grams of carbs for highly fit and active people.
Start intermittent fasting
Once you’ve gotten through the first week or so on a ketogenic diet, you’ll need to start an intermittent fasting practice. (You can choose to do prolonged fasts later on, but first things first, right?)
You can select from the following fasts:
- Time-restricted eating – eating all your meals within a 12-4 hour window, and fasting for the rest of the day
- 16/8 – fasting 16 hours per day, and eating all your meals in an eight-hour window
- OMAD (one meal a day) – eating dinner and fasting all the way to dinner the next day
- Alternate-day fasting – fasting every other day, and eating whatever you like in a 12-hour window on eating days. (Up to 500 calories can be consumed on fasting days)
- 5:2 – fasting on any two non-consecutive days out of the week, then eating whatever you want on the remaining five days
- 24-hour fasts – fast for 24 consecutive hours once or twice per week (lunch to lunch, dinner to dinner, etc.)
Doctors recommend starting with smaller fasts, like 12-hour daily fasts, and working your way up from there. And with ketogenic fasting, it’s perfectly acceptable to drink fat-containing beverages in the morning to help you achieve your fasting window. (Once you become fat-adapted, this usually isn’t necessary.)
Simply limit your calorie intake to about 1,200 per day, and stick to around 80-90% fat. This can involve a few Bulletproof coffees, a couple fat bombs, and some fatty meat.
“The ketogenic diet and intermittent fasting are very similar,” said Thomas Delauer, fitness influencer, and fasting/keto expert. “The whole idea of intermittent fasting is that you’re abstaining from food so that your body creates ketone bodies. And when it comes to ketosis, you’re eating foods that are going to help your body stimulate ketones,” he said. Putting the two together can lead to more weight loss than either one alone.
Beth Zupec-Kania, RDN, CD
Beth Zupec-Kania is a world-renowned ketogenic expert, clinician, and speaker. She is a registered and certified dietitian and nutritionist.
For over 25 years, she has coached medical professionals, patients, and families through safe and effective use of nutritional ketosis for neurological disorders, certain cancers, and other metabolic based conditions that require careful formulation and laboratory surveillance.
She is author of The Pocket Guide to Ketogenic Therapies for Neurological Disorders of which 100% proceeds from net sales of the book are donated to The Charlie Foundation for Ketogenic Therapies which was founded in 1994 to provide information about diet therapies for people with epilepsy, other neurological disorders and select cancers.
"There isn’t just one ketogenic diet; Beth explained there are several variations ranging from the strict “Classic” ketogenic which requires weighing food on a scale and strict meal plans to a flexible ketogenic diet that allows you to track macronutrients throughout your day. These different diets allow people to choose which therapy they can most easily manage. Some people like to start out with a flexible diet then after they see some benefit, they become stricter. Others start out strict then become more flexible."
Dr. Eric Burg
Dr. Eric Berg, health educator and fasting expert, says that reducing insulin is one of the most important reasons to try ketogenic fasting.
“With the ketogenic diet, he said on his YouTube channel, “you’re lowering insulin by eliminating carbohydrates and eating more fat. Intermittent fasting works because you’re eating less frequently,” which further reduces insulin production. Dr. Berg says that the combination (of keto and fasting) “works really, really well together.”
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