Both intermittent fasting and ketosis have gotten much attention lately.
Since Yoshinori Ohsumi was awarded the Nobel Prize for discovering autophagy – a primary health benefit of fasting – in 2016, intermittent fasting became socially acceptable (Levine et al. 20171).
Therefore, more and more people are discovering that intermittent fasting works with ketosis and that you can comfortably combine it with keto.
Regular intermittent fasting has many benefits, from being healthy to simplifying everyday life. Furthermore, these benefits can be even more significant if you combine them with a ketogenic diet!
What Is Intermittent Fasting?
Intermittent fasting (IF) has become popular due to its proven benefits. It involves eating within a certain period and fasting for the rest of the day.
Types of Intermittent Fasting
Various widely practiced forms of intermittent fasting exist. Among them, the most popular daily plan involves fasting within a time window of around 16 hours.
Intermittent Fasting 16/8
During the classic 16/8 intermittent fasting, you only eat between noon and 8 PM. So your body can rest for 16 hours with an 8-hour eating period.
Although you can postpone this time window according to your needs, it guarantees that the time outside this window (even while you sleep) allows your intestines and digestive tract to rest.
Since you usually sleep 8 of the 16 fasting hours, intermittent fasting is much easier than most people think. Accordingly, there are just two rules to implementing intermittent fasting into your everyday life:
- Skip breakfast
- Stop snacking
Due to the hormone release in the morning and its energy, it is unnecessary and only the most essential meal for the food industry.
One Meal A Day (OMAD)
The OMAD Diet is instead an extreme form of conventional intermittent fasting than a diet. Therefore, One Meal A Day means that you only eat once a day and fast the rest of the day.
Accordingly, it is similar to intermittent fasting 16/8 and is often referred to as the intermittent fasting 23/1 schedule or 23/1 diet.
Since OMAD is even simpler, I like to use it flexibly when it fits into my daily schedule.
One-Day Fasting (6:1 Diet)
A further interesting intermittent fasting method is one-day fasting or 6:1 diet. Accordingly, you don’t eat anything for one day a week and drink only water, coffee, or tea (without additives).
Since you don’t eat for at least 32 hours, you can get deeper into autophagy and ketosis during this day. Especially for athletes and people who don’t want to limit themselves daily, 1-day fasting is a popular option.
Alternate Day Fasting (ADF)
This method is as simple as it sounds. You eat one day and fast on the next one, the “Alternate-Day.”
However, I am not enthusiastic about ADF since most people eat a small meal (about 500 calories) on fasting days.
Moreover, it is much more challenging for many people to integrate it into their daily life.
Furthermore, with this more extreme variant, ADF is often used by people who want to justify their unhealthy high-carbohydrate diet on feasting days.
For this reason, many people fail miserably with this fasting method. In contrast to intermittent fasting and keto, two fundamentally different worlds collide this way.
As a result, people experience side effects and don’t reach their health and weight loss goals.
Health Benefits of Fasting
Fasting is entirely natural. Only this way, our ancestors could survive winter when food was scarce or unavailable.
Accordingly, many indigenous peoples still do not eat for days if they are not successful in hunting. Although we don’t rely on this survival mechanism anymore, we can realize its benefits by fasting regularly:
Fasting induces autophagy, a natural cleansing mechanism that replaces broken cell parts with new ones and detoxifies the body.
Accordingly, autophagy is one of the most incredible health benefits of fasting.
While this fasting detox helps prevent cancer, diabetes, liver, or autoimmune diseases, it also slows aging (Levine et al. 20172).
Like a ketogenic diet, fasting can improve results in terms of longevity and age-related diseases.
In addition to autophagy, reducing inflammation in the body immensely contributes to this anti-aging effect.
When fasting and with ketosis, the body uses fat instead of glucose as the primary energy source.
Thus, intermittent fasting and keto lower blood sugar and insulin levels, decreasing inflammation markers, free radical production, and modern diseases.
Moreover, elevated inflammation markers are the primary sign of an advanced aging process.
Contrary to conventional wisdom, fasting does not affect metabolism negatively. On the contrary, science proved intermittent fasting boosts metabolism decades ago (Drenick et al. 19643).
So, since there are good reasons for intermittent fasting, let’s look at how the interaction of intermittent fasting with ketosis can yield even more benefits.
Does Intermittent Fasting Put You Into Ketosis?
Since ketosis means the body has depleted carbohydrate stores, it can tap into body fat for energy.
Because the body spreads this fat energy through so-called ketones via the bloodstream, this natural fat burning is called ketosis.
For this reason, fasting is the most effective way to get into ketosis faster.
Because the keto diet tries nothing else but to achieve the same benefits as fasting via nutrition, you can combine intermittent fasting and keto so well.
And that makes intermittent fasting with ketosis even more efficient:
- Getting into ketosis faster: Combining a ketogenic diet with intermittent fasting helps you reach ketosis faster, so you can reap more profound benefits earlier.
- Fewer side effects: A ketogenic diet also reduces common side effects of intermittent fasting, such as the keto flu or an upset stomach.
- More energy: Since it amplifies ketosis and autophagy, many people report gaining mental clarity and power when combining keto with intermittent fasting. Due to elevated adrenaline, productivity often increases as well.
- Stability: Due to so-called fat- or keto-adaptation, the body no longer has to switch between burning glucose and fat for energy frequently, increasing well-being.
If you were already in ketosis before starting intermittent fasting, your body could tap into body fat for energy faster.
Since the ketogenic diet helps control your appetite and stay full longer, you can get used to extended periods without food more comfortably.
If you want to lose weight with intermittent fasting, combining it with keto is a way to lose weight faster.
The improved fat-burning abilities of intermittent fasting with ketosis and lower insulin levels enable you to reach or maintain a healthier body weight faster.
Moreover, you can break a weight loss plateau more quickly this way.
Intermittent fasting also trains the body to get used to absorbing the calories of a day in a shorter time frame, which sometimes relieves your digestion and improves gut health.
When you are used to intermittent fasting and keto, you relearn to eat when hungry. Accordingly, appetite is often learned and therefore tied to standard meal times.
Since intermittent fasting and a diet high in refined carbohydrates reduce health benefits and cause side effects such as brain fog, headaches, and blood sugar roller coasters, they don’t do well together.
If your body also burns fat for energy during the eating windows, you can support your brain through ketosis and prevent mood swings.
Furthermore, since sugar is eight times more addictive than cocaine, it is a fatal ingredient for your mood during intermittent fasting (Lenoir et al. 20075).
Boosting Ketosis with Intermittent Fasting
If you break the fast with a meal, you can even remain in ketosis when combining intermittent fasting with keto.
Because by eating high-fat, low-carb (LCHF), the body mimics fasting while simultaneously receiving an enormously high density of nutrients.
While fasting brings diverse health benefits, intermittent fasting with improved ketosis through a low-carb diet is way more effective.
As a result of combining intermittent fasting with keto, you can reap the following remarkable benefits:
- Improved ability to burn fat
- Improved insulin sensitivity
- Saved time and money
- Improved metabolic rate
- Improved muscle gain
- Cell renewal through autophagy
- Reduced inflammation
- Improved cognition
- Improved gut health
- Increased weight loss
The Bottom Line
Since intermittent fasting and a ketogenic diet use ketosis to burn fat for energy, they do incredibly well together.
However, intermittent fasting is not a must to reach ketosis.
So if fasting is not for you or does not fit into your everyday life, you can still follow a ketogenic diet and gain similar benefits.
But on the other hand, you won’t reap the more profound benefits of intermittent fasting without a lower-carb diet.
Because if your body has to burn through full carbohydrate stores before entering ketosis, you have significantly less time to burn fat while fasting.
Nevertheless, my experience is that intermittent fasting makes everyday life easier rather than more complicated. Accordingly, it saves time and money.
If you are into intermittent fasting, check out my article about the One Meal A Day (OMAD) schedule, which I use to bring even more flexibility and efficiency into everyday life.
Frequently Asked Questions (FAQ)
Does intermittent fasting put you in ketosis?
Yes, intermittent fasting can put you into ketosis. Ketosis is burning fat for energy when carbohydrate stores are empty.
How long does it take to go into ketosis when fasting?
If you are on a ketogenic diet, you are already in ketosis when fasting and burning fat for energy efficiency. On the other hand, if you follow a standard American diet (SAD), you will not get into ketosis in 16 hours since carbohydrate stores are full. In this case, you would need to go cold turkey with a prolonged fast to have a chance to enter ketosis.
How long does it take for intermittent fasting to reach ketosis?
It depends on how fat-adapted you are. If you are not used to low-carb diets, it can take weeks of 16/8 until you reach ketosis for the first time.
Will Diet Coke kick me out of ketosis?
A single diet coke won’t kick you out of ketosis. But since aspartame in diet coke elevates insulin levels, frequent consumption can kick you out of ketosis.
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2Levine B, Klionsky DJ. Autophagy wins the 2016 Nobel Prize in Physiology or Medicine: Breakthroughs in baker’s yeast fuel advances in biomedical research. Proc Natl Acad Sci U S A. 2017 Jan 10;114(2):201-205. doi: 10.1073/pnas.1619876114. Epub 2016 Dec 30. PubMed PMID: 28039434; PubMed Central PMCID: PMC5240711.
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Stephan is a writer and a true man of science, holding multiple diplomas and master's degrees in different research areas. His greatest passion is closing the gap between the conventional perception of health and the latest scientific evidence – always following the data.