Will Bulletproof Coffee Break your Fast?

Will bulletproof coffee break your fast?

If you’re regularly reading articles and learning about fasting and keto, you must have heard about bulletproof coffee. Coffee with added butter and MCT oil is used to give you focus and energy in the morning. But since fat has calories, it should break your fast right?

Any version of bulletproof coffee will break your fast. It won’t raise blood sugar and it will promote ketone production, helping you get into ketosis. It could even prevent some fat burning because the body will rely on the MCT oil ketones for energy, rather than your fat cells.

But that’s really not all there is to it. Bulletproof coffee has many benefits. You’ll see that even if it technically breaks a fat, it might be a great help to an intermittent faster or a keto dieter.

What is bulletproof coffee

Before diving into the effects of bulletproof coffee on fasting habits, keto and your body in general, let’s take a look at what exactly is this bulletproof/keto/butter coffee.

Bulletproof coffee under its current name and form was created by entrepreneur Dave Asprey, after going to Tibet in the 2000s and discovering yak butter tea.

While trekking at 18,000 feet, Asprey was struggling with energy, until a local in a guest house handed him a creamy butter tea. He immediately felt a rush of energy from the beverage. Back in the states, he tried to recreate this drink and the feeling he got from it.

His version of butter yak tea became bulletproof coffee. Substituting tea for coffee, yak butter with grass fed-butter. Finally, he added MCT oil to the mix, which really was the missing ingredient to pump up energy levels. Once marketed correctly (Dave’s not a successful Silicon Valley entrepreneur for nothing), bulletproof coffee became huge and one big addition to the keto and fasting trend.

Actually, mixing coffee with animal fat is far from being a novelty. Yak butter tea’s been around for decades in certain parts of Asia. And looking way back, around 575 to 850 CE, Ethiopian warriors, even before coffee was available in its current form, were crushing coffee beans and mixing them with animal fat. They used this snack as energy during long trecks.

Since 2010, when Asprey posted his own Bulletproof Coffee recipe, not forgetting to add in its very own Brain Octane Oil as the core element of the coffee, bulletproof coffee became somewhat of a cult.

What is the basic recipe?

  • 1 cup of coffee (8-12 ounces)
  • 1-2 teaspoons of MCT oil
  • 1-2 teaspoons of grass-fed butter or ghee

You mix those in a blender and voilà! You get bulletproof coffee. I personally only mix plain coconut oil with coffee. But you’ll see later in this article that it’s not the same thing as actual bulletproof coffee.

My daily routine of adding coconut oil to my coffee
My old daily routine of adding coconut oil to my coffee, now replaced by MCT + ghee

You might think that adding fat to a coffee is a sure way to gain weight. If taken with fasting or a keto diet, the fat will immediately be burned as energy. How? Well, there are two ways to fill up fat cells.

If you eat enough carbohydrates, your body will start a process called de novo lipogenesis, in short, new fat making. When you eat carbs, receptors will raise insulin levels in order to deal with the elevated blood sugar. Some of the carbs you ate will start by filling up your glycogen stores. These are your energy tank and you can find them in the liver and the muscle.

Then some of the glucose, if needed, will enter mitochondria, which is the body’s powerhouse, and it will be burned as energy for your muscles and brains.

Lastly, the remaining glucose will be stored as fat in your fat cells for later use. Fat cells simply are a long term energy store, they aren’t just there to make you fat and fill miserable.

The other way you can fill up fat cells is by a process called re-esterification. This process consists of taking fatty acids in your body and forming them back into fat to be stored.

When your body is taking fat out of your fat cells, this process is called lipolysis. When you’re in ketosis, either from fasting or low carb diet, your body lipolysis levels will be up. When lipolysis is up, re-esterification is down, and vice versa.

So if lipolysis is up in ketosis and you drink fat coffee, your body will simply turn to the fat in the coffee for immediate energy. But this process won’t completely stop lipolysis and re-esterification won’t happen.

Now, even though studies show that drinking coffee, even with a high carb breakfast, can improve ketones production, it’s not advised to add in the butter and MCT oil when getting carbs.

If you eat carbs, insulin levels will rise. Insulin will increase re-esterification and inhibit lipolysis. Meaning all the fat you’ll get in addition to the carbs will go through to process of re-esterification: fatty acids will be turned back to fat to be stored.

All that to say that coffee, and moreover, bulletproof coffee will improve ketosis, but you should really drink the later only with low carb meals or, even better, with no food at all.

Will bulletproof coffee break your fast

Yes, adding fat to your coffee will break your fast.

MCT oil contains 8 calories per gram, compared to other fats that contain 9, but they still elicit a metabolic response.

It won’t raise blood sugar and it won’t produce much of an insulin response. You might already now that when compared to carbs and proteins, fat has a very low insulin response.

Insulin response to protein, fat & carbs – diabeticstrong.com

What exactly does it mean to break a fast with bulletproof coffee though? Well, there are three big advantages to fasting:

  1. getting into ketosis
  2. losing weight
  3. detox

Will it prevent you from getting into ketosis

Ketosis happens when you restrict carbs intake for long enough. Meaning your body will have burnt all your energy stores in your liver and muscles. It will then turn itself to fatty acids from the diet (low carb diet of course) and the body fat for energy.

When doing this, your body enters ketosis. It will actually run on ketone bodies, that will be created by breaking down fatty acids and fat cells for energy. Ketones are an alternative source of energy for the body. It’s the preferred source of energy for the brain (I’ll talk about it later).

So, will drinking bulletproof coffee prevent ketosis? Hell no! It will improve ketosis and help you get into ketosis. MCT oil is short for medium chained triglycerides. MCTs are known to be :

  • Absorbed quicker
  • Turned into energy more efficiently
  • Result in less body fat gain and feeling satiated faster
  • And lastly: it improves ketones production

When you get into ketosis, your body might react with dizziness, fatigue, headache, etc. This state is known as keto flu. Bulletproof coffee might actually help people get in ketosis faster. If you want to do a strict fast, don’t drink butter coffee. But if your goal is to get into ketosis and if you’re following a keto diet, definitely use it.

Even though it would technically break a fast, I wonder if it wouldn’t be a good addition to a prolonged fast. Getting bulletproof coffee in the morning for the first two days might help get through the most difficult days (get into ketosis and feeling satiated).

Will it prevent you from losing weight

That’s kind of a tricky question.

First off, if you’re fasting and you drink bulletproof coffee, the immediate effect might be to prevent your body from burning fat. Think about it, your body is relying on your body fat for energy, since you’re not getting energy from your diet.

But when you drink bulletproof coffee, you actually get some energy, in the form of ketones from the good fat you’re getting. This could stop the process of fat break down since your body can then rely on your diet for energy.

That’s the short term answer, but what about the long term? As I said, bulletproof coffee will increase ketones in the body and help you get into ketosis. Coffee and MCT both promote thermogenesis, increasing your metabolic rate.

Your metabolic rate is the number of calories your body can burn within a given time. So, the beverage could help promote weight loss by helping increase the metabolic rate. This could help if you’re fasting for a whole day and you’re getting bulletproof coffee in the morning. But it could also improve metabolic rate in the long term, elevating the effect of fasting or keto (which is already known to do just that).

Another well-known side effect of bulletproof coffee is that it will make you feel satiated more quickly, since the fat will immediately be used for energy, telling your body that it doesn’t need more for the time being.

Will it stop autophagy

Bulletproof coffee might also prevent autophagy.

Autophagy is a process your body goes through when fasting. We might say it’s the “detox” aspect of fasting. During this process, your body will repair itself, recycling damaged proteins, microbes, viruses, candida, cleaning stuff.

When you’re in autophagy, usually the need for vitamins and nutrients goes down. Our body was designed not to eat frequently, autophagy is actually a survival skill, think of it as some kind of self-cleaning oven. When you don’t eat for long enough your body will trigger autophagy to self-clean itself.

Usually, depending on people, autophagy will start at around 16 to 18 hours of fasting. So, a sure way to trigger autophagy and get some benefits from it would be to do one meal a day. But this process is very hard to study and there are many factors that can prevent autophagy anyway.

Depending on your age, weight, overall health, it could take longer to get into autophagy. A sure way to prevent it is also to have some insulin in the body. You might say, why would we have insulin in the body if we’re fasting? It might happen if you’re insulin resistant. Meaning eating carbs will release a lot more insulin than it would in a healthy person. So insulin could remain in the body for a while.

Of course, glucose and proteins will stop autophagy, as well as cortisol. Cortisol is the stress hormone, so when fasting in a highly stressed state you could actually prevent autophagy.

Since fat has a very low insulin response, will bulletproof coffee prevent autophagy? There really aren’t real actual data on the subject. But it would highly depend on:

  • Your health
  • The amount of the quality of the fat
  • Exercise routine (helps your body getting into autophagy)
  • How fast is your metabolism

In short, bulletproof coffee can break autophagy, but a tablespoon of MCT oil, for example, might not be that significant if you’re young, healthy and exercising every day. Of course as always, if you want to be sure not to break autophagy, don’t drink it.

What are the benefits of bulletproof coffee

Let’s take a look at the three main ingredients of bulletproof coffee in order to understand what are the benefits of each of them.

MCT oil

The MCT Oil I now use daily
The brand of MCT that I use – In the US, you can get the one from Bulletproof

MCT is short for medium-chained triglycerides. MCTs are :

  • Absorbed quicker than long-chained triglycerides
  • Turned into energy more efficiently

MCTs cross through the double membrane of the mitochondria, which is the cell powerhouse of the body, to give it a lot more energy ready to be used as-is.

You might wonder what type of food MCT oil comes from? Mainly, it will be manufactured from coconut oil. I talked about coconut oil earlier, I’ve been using it as a substitute to MCT oil for a while now. Coconut oil is actually one of the only natural sources of MCT.

But coconut oil and MCT oil are not the same things. Coconut oil is contained of :

  • A very small amount of C6 MCT (also called caproic acid)
  • Around 6% of C8 MCT (caprylic acid)
  • 10% of C10 (capric acid)
  • Around 60% of C12 (lauric acid)

Pure MCT oil is generally composed of C8 and C10, C6 being very rare. As you would probably assume, the shorter the chain (6, 8, 10, 12), the faster the fatty acid will be turned into ketones.

So, when you get coconut oil, you’re mostly getting lauric acid. Lauric acid is kind of a pseudo-MCT. It will respond mostly as a long-chained triglyceride would, meaning it will still go into the liver for conversion when other MCTs won’t.

MCT oil basically is coconut oil from which you would have removed the long-chained “acting” fatty acid lauric acid.

Side note: coconut oil is great, it is still the biggest natural source of MCT out there. And even though lauric acid doesn’t have the desired cognitive effects of other MCT, it is known to have huge digestive and immune benefits.

The advantages of MCT are that it will:

In short, the MCT part of the bulletproof coffee will give you intense focus and energy and leave you feeling satiated.

Grass-fed butter

The butter won’t have any performance-enhancing effects, but it will help with the creamy consistency and help keep you satiated.

It is quality fat and a good source of :

  • Vitamin A
  • Vitamin E
  • Vitamin K2
  • Omega 3
  • Antioxidant (glutathione)

This by no means means that bulletproof coffee is packed with vitamins, but it’s a welcome bonus.

But in short, the grass-fed butter is mostly another source of fat used to get the coffee the consistency of a latte. And it’s also a good fat addition when doing a keto diet, since it’s a low carb, high-fat diet, it can sometimes be hard to raise fat intake to 60% on certain meals.

The brand of organic Ghee I use daily
The brand of ghee I use daily – Again, in the US, you can get the one from Bulletproof

For those of you who are lactose intolerant, you could use ghee rather than butter. Ghee is actually clarified butter. Butter is 80% body fat, 16 to 18% water, and 2% milkfat. When boiled you get rid of the water and most of the milk bodies, this leaves you with clarified butter.

Ghee is taking it one step further, caramelizing the leftovers milk solid, giving it a rich nutty flavor and leaving ghee with a 99.6% milk solids-free.

A study showed that those who consume ghee butter, as opposed to normal butter, ended up with a massive reduction in overall cholesterol (around 25%) and an 18% increase in HDL cholesterol (good cholesterol). Indicating it removes bad fats in the bloodstream.


The final ingredient, coffee, will be kind of like the glue holding everything together. It will help mobilize the fats out of the cell and into the bloodstream, in order for them to do their job.

But that’s not all, coffee, by itself, is also known to boost ketones productions in a dose-dependent manner. Meaning the more caffeine you get, the more ketones production. The study below was done with subjects eating high carbs breakfast with their diet. And insulin is known to decrease ketones production.

Caffeine stimulates ketones production in a dose-dependent manner – Source

So, this means that coffee, taken on a fast or keto diet, would be even more efficient to stimulate ketones production.

Related questions

Isn’t bulletproof coffee full of saturated fat? Yes, it is. But it is good fat, the saturated fat, and cholesterol in grass-fed butter helps on a hormonal level (steroid and sex hormones) and the MCTs increase your metabolic rate. You don’t necessarily need to have it every day, but I would drink bulletproof coffee against normal, high carb, breakfast any day.

Can I add artificial sweeteners to bulletproof coffee? You can. I did a whole article on artificial sweeteners and, while they don’t break a fast by themselves, I still wouldn’t consider it a good habit to add to your everyday meals or drinks. It’s still highly manufactured food. But, in a way, so is MCT. Oh well. 🙂

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