Can you drink coffee while intermittent fasting?
That‘s probably one of the most frequently asked questions about fasting. But if you are just starting, don’t worry too much about it.
By deciding to promote your health through intermittent fasting, you already belong to the caring top 5% of humanity.
Besides everything you need to know about coffee during intermittent fasting, I will show you some hacks that can prolong fasting without effort.
Intermittent Fasting and Coffee
To answer whether you are allowed to drink coffee during intermittent fasting, we must first look at the effects of coffee on intermittent fasting and its benefits.
Every engine must be maintained, no matter how well it’s built. The same applies to your body. Fortunately, nature has already provided for this.
Fasting induces autophagy, a natural cleansing mechanism that replaces broken cells with new ones and drains toxins from your body.
Accordingly, autophagy is one of the most significant health benefits of fasting. Therefore, the discovery of autophagy was awarded the Nobel Prize for Medicine in 2016 (Levine et al. 20171).
Furthermore, it can slow aging (Gelino et al. 20122).
Fasting is one of the best ways to activate autophagy (Bagherniya et al. 20183).
Coffee also helps to activate autophagy. So you can increase the benefits of fasting with coffee (Pietrocola et al. 20144).
Coffee drinkers more efficiently maintain weight over the long term (Icken et al. 20175).
Coffee reduces appetite could be a good reason for this (Greenberg et al. 20126).
Also, coffee increases the metabolic rate. Hence, coffee is particularly beneficial for weight loss (Acheson et al. 19807).
Therefore, the combination of coffee and intermittent fasting can help you to stay fasted longer and lose weight quicker.
If you don’t eat, your body uses up its carbohydrate stores and then burns body fat for energy.
Since your body delivers fat energy to all corners of the body as ketones, this fat-burning state is called ketosis.
Thus, fasting is an easy way to get into ketosis faster.
Therefore, you can easily combine intermittent fasting with a ketogenic diet. In short, the keto diet tries nothing else but to achieve a state similar to fasting and its benefits through diet.
Accordingly, fasting helps enormously with the keto diet. But drinking coffee while intermittent fasting can boost fat burning even more significantly.
Because according to recent research, coffee gives an additional boost to ketosis during fasting (Vandenberghe et al. 20178).
As with the ketogenic diet, elevated insulin levels are a problem with fasting. Since the storage hormone triggers the switch from fat burning to fat storage, it is better to keep it low.
Moreover, it suppresses the fat-breakdown enzyme in the human body (Meijssen et al. 20019).
In the long run, fasting is one of the most effective methods to improve insulin sensitivity and, thus, glucose metabolism. Therefore, intermittent fasting helps to prevent diabetes.
Nevertheless, fasting can reduce insulin sensitivity in the short term. Since this reaction has an excellent reason, it is harmless.
Because the body ensures that the majority of glucose available is delivered to the brain, some other cells become acutely insulin-resistant. For this reason, those parts of the brain that cannot run on ketones and need glucose can get enough of it.
But don’t panic, as the liver synthesizes sufficient glucose from amino and fatty acids during fasting (Merimee et al. 197410).
Coffee has a similar effect. Acutely, coffee reduces insulin sensitivity and glucose tolerance. Therefore, never add sugar to coffee or pair it with cake.
However, coffee improves insulin sensitivity and glucose metabolism in the long term. For this reason, recent studies show that coffee reduces the risk of type 2 diabetes (Carlström et al. 201811).
Can You Drink Coffee While Intermittent Fasting?
Block coffee does not break your fast. A cup of black coffee contains 1-4 calories and minimal amounts of protein, fat, and trace elements. The same applies to decaffeinated coffee.
The nutrients in 1-2 cups of black coffee cannot influence most people’s metabolism to break the fast (van Dam et al. 200412).
Since coffee can help suppress appetite, it helps many people to extend fasting periods.
However, enormous quantities of coffee can undoubtedly influence intermittent fasting. Since coffee stimulates the hormone adrenaline, it can trigger energy release, such as while experiencing acute stress (Smits et al. 198613).
For this reason, glucose can indirectly enter the bloodstream without food intake (Sherwin et al. 198414).
As long as you do not drink more than 1-2 cups in a short time frame, coffee will not significantly affect intermittent fasting.
Nevertheless, it can become more critical during prolonged fasting (24+ hours). Although there can be no generic answer here, I would not drink more than 5 cups of coffee.
And these should be spread throughout the day. That way, you are on the safe side. Rough amounts, such as 10 cups a day, can influence fasting.
But what about milk, creamer and other popular additives in your coffee?
What Can I Put In My Coffee During Intermittent Fasting?
The list of possible coffee additives is long nowadays, so I try to cover all the popular options, from different milk products to spices. You might be surprised how different the effects on your metabolism can be.
Heavy cream breaks a fast. However, it is a better alternative to milk if you want to lose weight.
100g of heavy cream contains about 3g of milk sugar (lactose) and protein. Although some heavy cream does not necessarily inhibit fat burning, they will negatively affect autophagy.
Thus cream breaks your fast. However, that doesn’t mean that a splash of cream destroys all the benefits. Fasting benefits such as autophagy do not have a binary switch. Nevertheless, heavy cream will inhibit results.
Nonetheless, heavy cream can be a welcome ingredient in a ketogenic diet since it helps to promote autophagy in the long run.
A coffee creamer breaks your intermittent fast. Creamers and similar additives in powder form are highly processed. Therefore, these are absolute junk!
They are loaded with carbohydrates, proteins, and fat. Moreover, some creamers consist of up to 50% sugar.
Also, coffee with sugar-free creamer isn’t an option. Besides too much protein and fat, you will find other artificial additives like sweeteners.
If you like your body, you should avoid these junk additives during fasting.
Unfortunately, milk breaks your fast.
100ml of milk contains almost 5g lactose and approximately as many proteins.
The calculation here is simple. With intermittent fasting, milk makes the difference in coffee. Even a dash of milk detracts from the benefits of fasting.
Coffee with milk breaks the fast.
What about skimmed milk?
Skim milk breaks a fast. Even with milk, the low-fat variant makes everything worse. As with other low-fat products, more sugar is hidden in skim milk. And, of course, less fat to counteract it.
In short, with skimmed milk, blood sugar and insulin levels rise even faster. That’s why cereals with milk, for example, are one of the worst meals for your health – not only when you’re on a ketogenic diet.
Also, skimmed milk is out. What about half and half milk?
Half and Half
Half an half in coffee breaks your intermittent fast. Since cream and regular milk can break a fast, half and half can. Due to the significant mix of protein and carbs, half and half inhibit fasting benefits.
Furthermore, half and half are more likely to contain processed additives.
So regular kinds of milk are not safe for fasting. Can coffee with almond milk be an alternative for intermittent fasting?
Tiny amounts of unsweetened almond milk are OK during intermittent fasting. However, steer clear of soy- and rice-based almond drinks.
As long as you avoid the sweetened or protein-enriched versions and only add a shot, the effects of almond milk in coffee are negligible.
Nevertheless, almond milk technically breaks the fast. Therefore pure nut milk is not suitable as a drink during fasting.
Oat Milk breaks your fast. Since the food industry jumped on the vegan hype train, oat milk is currently enjoying great popularity.
But have you ever thought about the fact that it might be unnatural to make a milk substitute from grains? Where does the fat content come from, which you need for creaminess?
As I suspected, the fat in popular brands comes from industrially processed vegetable oils, such as canola oil.
To produce oil artificially from a non-oily plant is unnatural and harms your health significantly.
Since chemical processing damages susceptible omega-6 fatty acids, they promote free radicals in your body.
Accordingly, your body should probably not use these broken fats as essential building blocks of your brain cells. Don’t you think so?
Hence, for people who are intermittent fasting for health reasons, oat milk is not an option.
So, what about weight loss?
Besides the 7.5 grams of fat from canola oil, a glass of oat milk has a staggering 16.5 grams of carbohydrates, of which 10 grams are table sugar (*).
Thus, we no longer need to debate. That’s the last nail in the coffin for oat milk during intermittent fasting.
Since even a shot of oat milk triggers a blood sugar and insulin spike, you better put it into the sink.
Soy milk breaks an intermittent fast. But is it a better alternative to milk?
One glass of soy milk has about 15.5 grams of carbohydrates, of which 10 grams are table sugar (*).
As with oat milk, industrially produced omega-6 fatty acids predominate in this artificial drink.
Furthermore, soy is one of the world’s three most frequently genetically manipulated crops. Accordingly, over 90% of the canola, corn, and soy harvest comes from genetically manipulated plants.
Why should your soy drink be non-GMO?
On the one hand, this is almost impossible to find; on the other hand, it is highly unlikely.
Since soy probably comes mainly from a foreign country, the first processing steps happen somewhere, neither traceable nor regulated.
So what’s the solution?
Eat real food! Industrially produced drinks mixed in a lab are harmful to your health – no matter what the commercials say.
However, a single shot of soy milk breaks the fast due to the high carbohydrate intake.
With this in mind, if you need a milk substitute while eating due to an intolerance, go with unsweetened almond milk.
Tiny amounts of cocoa do not break a fast. Although some cocoa powder is fine, you should pay attention to the amount.
Since the cocoa powder is made from whole cocoa beans, it contains carbohydrates, protein, and fat. Therefore, more than a teaspoon of cocoa powder will break the fast.
There are two things to pay attention to with cocoa powder:
- It must be unsweetened
- Ideally, it is degreased too
Cinnamon is okay as an additive. Moreover, it is a proven remedy against appetite and cravings. Therefore, it is welcome in our coffee during intermittent fasting.
Furthermore, cinnamon can even help to reduce insulin resistance. For example, the one you get due to lack of sleep.
Nevertheless, it is also true that more significant amounts of coffee can impair autophagy.
Just like cinnamon, a little nutmeg can help against an acute appetite. Nevertheless, avoid excessive amounts as they can cause side effects.
Should I Drink Bulletproof Coffee While Fasting?
The essential aspect of every Bulletproof Coffee is the addition of high-quality fat. Hence, Bulletproof Coffee is not an ordinary coffee with cream.
It is a keto-friendly coffee drink popular with intermittent fasting enthusiasts.
Also, many athletes or professional high performers drink Bulletproof Coffee. They all swear on Bulletproof Coffee to get an energy boost from quickly metabolized fat.
For this reason, they leverage Bulletproof Coffee to complete tasks more efficiently and faster. Since this power drink helps you stay saturated, awake, and concentrated, it is a keto and intermittent fasting staple.
The classic Bulletproof Coffee recipe contains two essential ingredients besides black coffee:
- Quickly metabolizable MCT or coconut oil
- High-quality grass-fed butter or ghee
MCT stands for medium-chain triglycerides.
Since these fatty acids are derived from coconut oil, but MCT oil contains a far higher concentration, it is virtually the more powerful brother of coconut oil.
Since MCT oils can consist of caprylic acid (C8), which is only eight carbon atoms long, they can be metabolized more quicker than coconut oil.
Does coffee with pure MCT Oil break a fast?
Although pure fats usually have many calories, they do not affect blood sugar. Nevertheless, it is virtually a meal. And eating affects insulin levels.
In the case of pure fat, however, this happens only indirectly and minimally.
Technically speaking, any fat breaks a fast. Therefore, you will burn less fat due to Bulletproof Coffee during intermittent fasting. Nevertheless, the impairment is only minimal.
For the same reason, coffee with coconut oil suits fasting beginners. This way, you can counteract hunger and get used to intermittent fasting.
If you can fast for only 12 hours on black coffee when starting but can extend to 16 or 24 hours using a few teaspoons of coconut oil, the disadvantages of adding fat are acceptable.
Nevertheless, you will not need fat after a few days of practice to prolong intermittent fasting.
Butter and Ghee
Grass-fed butter gives classic Bulletproof Coffee a creamy consistency. It also contains high-quality fats that increase satiety and energy level.
Furthermore, grass-fed butter provides powerful nutrients such as vitamin A, beta-carotene, butyrates, or conjugated linoleic acid.
If you are looking for an allergy-friendly, shelf-stable option with almost no lactose, grass-fed ghee is your answer.
Butter, like coconut oil, ghee breaks a fast but should not significantly affect autophagy.
Although the intake of proteins interrupts this self-cleaning mechanism of the body, the amount in butter is negligible.
Ghee is even safer, as it is ultra-clarified butter without any lactose and protein.
Collagen and Whey Protein
The athletes among the intermittent fasting and keto enthusiasts love collagen in their Bulletproof Coffee.
Nevertheless, like whey powder, it is pure protein. On the one hand, protein activates the anabolic mTOR pathway for muscle building. On the other hand, it inhibits autophagy.
Therefore collagen offers muscle building, fat burning, and satiation benefits but breaks a fast.
Can I Put Sweetener in My Coffee During Intermittent Fasting?
Sweet taste is a much-discussed topic regarding intermittent fasting and the keto diet. On the one hand, it is difficult to get away from it. On the other hand, it substantially promotes cravings.
Most sugar-free sweeteners have zero protein, carbohydrates, and calories. Therefore, they do not raise the blood sugar level. But is the calculation that simple?
No, since people often forget that intermittent fasting and keto have one essential goal: Lowering insulin levels to allow your body to tap into stored fat for energy.
Since the storage hormone insulin prevents body fat breakdown and ketone production, a significant increase in insulin levels breaks the fast.
Unfortunately, most diet gurus have not done their homework in this context.
As endocrinologist and fasting pioneer Dr. Jason Fung correctly points out, it does not matter whether food increases blood sugar levels as long as it increases insulin levels (Fung 201615).
It’s off the table since sugar already increases blood sugar and insulin levels.
The high-calorie cocktail of glucose and fructose breaks your fast.
None of them provide carbohydrates, proteins, or calories. Nevertheless, studies show that they increase insulin levels significantly.
For example, sucralose increases insulin levels by around 20 percent (Pepino et al. 201316).
While aspartame, the classic sweetener in diet soda, does not affect blood sugar, it can increase insulin levels more than regular sugar (Anton und Martin et al. 201017).
Moreover, the artificial sweetener acesulfame potassium in zero drinks increases insulin levels like glucose (Liang et al. 198718).
Besides various other side effects, these sweeteners prevent fat-burning. Hence, artificial sweeteners are no safe option during intermittent fasting.
Xylitol is the most common sugar alcohol. However, it isn’t calorie-free.
Also, xylitol triggers a small but significant increase in blood sugar levels.
As this stimulates digestion, xylitol can break a fast (Natah et al. 199719).
In contrast, erythritol, another sugar alcohol, does not have this effect.
However, I would use this sweetener only occasionally, as it can cause addiction.
Both sugar alcohol sweeteners are marketed as natural sugar substitutes. Xylitol, the supposed birch sugar, is usually not made from birch wood but from straw or corncob remains.
Also, erythritol is produced industrially from carbohydrates.
In the case of xylitol, the process uses acids or lyes. In the case of erythritol, the procedure uses microbial fermentation.
Stevia breaks a fast. The often-praised sweetener stevia also significantly increases insulin levels.
Since many diet gurus haven’t carefully read a well-spread study, the common opinion about stevia is often incorrect.
Because consuming a meal with stevia does not reduce the blood sugar and insulin response, as is often claimed.
Compared to the same meal with table sugar, these reactions are sometimes minimally lower (Pepino et al. 201320).
“Natural” sweeteners such as stevia or agave syrup are processed industrially like table sugar. Also, the addictive white crystal comes from “natural” sugar beet.
Furthermore, agave syrup with up to 97% fructose is diabetes in liquid form.
Although stevia may be acceptable for dessert on special occasions, it is not daily during fasting.
Monk fruit breaks your intermittent fast. It extract has a similar effect to stevia. It is also extremely sweet – about 200 times sweeter than sugar.
Although monk fruit sweetener is one of the better alternatives, I wouldn’t use it daily for intermittent fasting due to its counterintuitive nature.
Studies show intense sweetness promotes appetite and cravings (Yang 201021).
The Bottom Line
Coffee can help while intermittent fasting. As long as you pay attention to what you add, coffee doesn’t break intermittent fasting. On the contrary, coffee can even boost fasting benefits.
In the end, it’s up to you. If a cup of coffee takes away your hunger during fasting, gives you energy, and makes you feel good, go for it!
Nevertheless, it would be best if you avoided large quantities.
Also, you can drink black or green tea while intermittent fasting. But be aware that milk and other additives to tea will have the same effects as in coffee.
Since they often contain candied fruit and other hidden sugars, I would pay close attention to herbal tea ingredients.
If you’d like to learn proper intermittent fasting playfully, get my free 30-Day Intermittent Fasting Challenge PDF printable.
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Frequently Asked Questions (FAQ)
Does coffee break intermittent fasting?
No, black coffee ☕ doesn’t break intermittent fasting. But coffee with cream or milk 🥛 does.
Can I drink coffee on the 16 8 Diet?
On a 16/8 intermittent fasting schedule, you can drink black coffee ☕ without milk and sugar while fasting.
Does milk in coffee break intermittent fasting?
Any cow’s or plant milk will break your fast, except a splash of almond milk.
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Mag. Stephan Lederer, MSc. is an author and blogger from Austria who writes in-depth content about health and nutrition. His book series on Interval Fasting landed #1 on the bestseller list in the German Amazon marketplace in 15 categories.
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