Does Bulletproof Coffee Break a Fast? Keto Coffee and Intermittent Fasting

Can you drink Bulletproof Coffee while fasting, or will it break your fast? There is a lot of gray areas regarding Bulletproof Coffee and intermittent fasting that you need to know about.

Bulletproof Coffee has been popular over recent years with benefits claiming it can help with weight loss, boost energy, improve mental clarity, and lower inflammation. It’s essentially coffee mixed with MCT oil and grass-fed butter.

Since butter contains calories you’d think it would break your fast, right? But not so fast!

The truth is there are some methods when drinking Bulletproof Coffee that won’t break your fast. But then there are other ways in which it will counteract the benefits of intermittent fasting. Here you’ll uncover everything you need to know to maximize your results depending on your goals.

In this blog post, we will explore the science behind Bulletproof Coffee and whether or not it breaks a fast. You’ll discover the pros and cons and whether drinking Bulletproof Coffee is a good idea. Let’s get into it!

Intermittent Fasting and Bulletproof Coffee

keto coffee fasting

To make Bulletproof Coffee, you only need coffee, MCT oil, and grass-fed butter. Blend in the MCT oil and butter with the coffee, and you have Bulletproof Coffee. It doesn’t sound like the most appetizing way to drink your coffee, but quite a few like it.

Bulletproof Coffee claims to be able to:

  • enhance weight loss
  • boost energy
  • improved brain function
  • reduce inflammation

To know if Bulletproof Coffee will break a fast you have to first breakdown n its ingredients and nutrition profile. Since there aren’t any carbs or sugars in Bulletproof Coffee then it won’t raise your blood sugar or cause an insulin response.

But butter is high in saturated fats and calories. The recommended amount of butter for Bulletproof Coffee is 1-2 tbsp. which comes out to 12-25g of fat and 102-204 calories per serving.

The MCT oil is broken down differently in your body than other calories. It’s quickly shuttled to your liver where it’s converted into ketones instead of being absorbed as calories into your bloodstream.

So adding MCT oil itself to your coffee won’t break a fast.

Does Butter and Bulletproof Coffee Break Intermittent Fasting

bulletproof coffee weight loss results

Whether or not Bulletproof Coffee (and the butter) will break your fast depends greatly on your goals. Most people are intermittent fasting for weight loss, and if that’s the case for you, then it’s acceptable to take when fasting.

Since Bulletproof Coffee shouldn’t cause an insulin spike, then by definition, it shouldn’t break your fast.

Bulletproof Coffee is all fat it will mostly be converted into ketones that your body can use for fuel. These ketones help to push your body into a ketogenic state that encourages burning fat stores for fuel thus leading to weight loss.

But the high amount of fat and calories in the butter shouldn’t get a “free pass.” There’s a “50-calorie rule” with dirty fasting that allows you to have something under 50 calories (no sugar) when fasting without it breaking your fast. Since the butter in coffee contains 100+ calories, then it breaks the rule.

Yet if you’re practicing the keto diet, then it won’t break ketosis.

Intermittent fasting isn’t like an on-and-off light switch. There is a lot of gray areas that allow some leeway, and you can still get results. Fasting purists believe anything other than water will break your fast. But just because Bulletproof Coffee can break your fast in that way, it doesn’t mean you can’t still get results.

Bulletproof Coffee will break autophagy if that’s one of your goals with intermittent fasting. 

The butter in Bulletproof Coffee is high in calories so it’ll most likely break the autophagy process of repairing and eliminating old damaged cells. Too many calories when fasting will raise mTor and thus shut down autophagy.

How Bulletproof Coffee Affects Fasting

Now let’s dig into the pros and cons of drinking Bulletproof Coffee when fasting.


It has zero carbs.

One thing is for certain… it’ll be better to drink Bulletproof Coffee in the morning when you’re fasting than it would be to eat a typical high-carb breakfast. Trading the morning bagel, cereal, oatmeal, donut, croissant, etc. for Bulletproof Coffee is going to be way more beneficial for weight loss.

Eating a low-carb diet combined with intermittent fasting is a surefire way to get some impressive weight loss results. Drinking Bulletproof Coffee in the morning will instantly cut back on all those breakfast carbs.

High insulin levels are one of the driving factors of weight gain. So it’s a worthy tradeoff to cut out those breakfast carbs for the high-fat and calories in Bulletproof Coffee butter.

It’s filling.

Plus the butter combined with the MCT oil and caffeine in Bulletproof Coffee is highly satiating. This helps to increase your feelings of being full. If drinking Bulletproof Coffee makes it easier to get through your fast, so you keep fasting longer then you’ll get better results in the long run.

You’ll be able to fast for longer and kick out the carbs, sugars, and other calories that you would otherwise be consuming during that same time.

More energy, mental clarity & less inflammation.

You’ll also get other benefits other than weight loss, such as an energy boost, better mental clarity, and reduced inflammation. The MCT oil and butter are converted to ketones that your brain uses as fuel.

This is a good idea to have more in the morning to increase productivity and get some work done. You also shouldn’t experience a morning “carb crash” that you’d normally get eating breakfast carbs.


The butter itself.

The biggest issue with drinking Bulletproof Coffee is the butter. It’s high fat and high calorie. It’s really pushing the boundary of breaking a fast while still giving you some of the results.

It can slow fat-loss.

All those fats when fasting can be converted to ketones, but it can also hinder fat loss. With all those ketones in your body when fasting, it’ll reduce the number of fat stores it’s burning for energy.

The trick is only to have some of these ketones in your body to encourage the burning of fat stores for fuel. But if you have too many, then your body won’t get to tap into its own fat stores because it’s full of ketones.

MCT oil plus the butter is pushing it and can walk the line on maximizing your weight loss results.

Accounts for a lot of daily fat + calories.

Plus the saturated fats can really start to add up. Your body does need some saturated fats to be healthy, but the 24g in Bulletproof Coffee already meets the daily allowance for many on a 2,000 calorie per day diet. So any more saturated fats in the day will push you over. This can be hard when you’re already consuming a low-carb diet.

Can You Have Bulletproof Coffee When Fasting?

when to drink bulletproof coffee

If weight loss is your goal, you can drink Bulletproof Coffee when fasting and still get results. It doesn’t fully break your fast like flipping off a light switch, but it can hinder some of your results. Keto coffee can enhance weight loss with fasting under certain circumstances.

If you’re used to eating a high sugar carb-rich breakfast, then drinking Bulletproof Coffee is preferred. If you’re insulin resistant and near diabetic, then it’ll also be way better for you to have Bulletproof Coffee in the morning than eating a couple of bagels.

Bulletproof Coffee can make you feel fuller longer too so it should make it easier to get through your fasting window. The hunger pangs are the most challenging part of intermittent fasting, so taking approved fasting drinks can make it easier to get through them. Plus, they even contain some ingredients like caffeine and MCTs that can accelerate your results.

You can essentially treat the Bulletproof Coffee as a morning meal replacement. It’ll be better in the long run than eating a bowl of Lucky Charms for breakfast.

You’ll not only cut down on sugar, carbs, and calories by drinking Bulletproof Coffee when fasting, but you’ll also get some of the ketogenic benefits as well.

When You Shouldn’t Drink Bulletproof Coffee When Fasting

should you drink bulletproof coffee when fasting

If you want to maximize your weight loss results, drinking Bulletproof Coffee isn’t the best choice.

The high amount of fat and calories in the butter can add up when combined with the rest of the food you’re eating during the day. Calories do affect weight management, so keeping them under control can be harder with the energy and fat density in the butter.

You could produce too many ketones when drinking Bulletproof Coffee when fasting. Some ketones are beneficial for an energy boost and mental clarity but then can also lower the amount of free fatty acids available for fat burning in your body. The trick is just to get some ketones to help flip the switch, so you start burning more of your own fat stores for fuel.

What I personally do and recommend instead…

I’ve personally tried Bulletproof Coffee for a while and found it not to be the best to drink when fasting.

The high fat didn’t sit well with me, and the high calories would be too much to really move the needle. I wouldn’t recommend drinking it every day unless you’re really into it and factoring in the meals for the rest of the day to keep you under the limit.

But I did find there’s a big benefit to drinking coffee and taking MCTs when fasting. Coffee contains caffeine that helps to boost your metabolism, encouraging fat burning. Plus, the coffee is satiating, helping to curb hunger when fasting.

And I kicked out the butter but still add C8-MCTs to my coffee. C8-MCTs are your body’s preferred source of MCTs, and they’re the most efficiently converted into ketones.

The MCTs are quickly converted into ketones by your liver and help to kickstart the fat-burning process. The keto diet is so effective for weight loss because it produces these ketones from your fat stores since you have no quick-burning carbs for fuel.

So by simply mixing the coffee with C8-MCTs you can maximize the benefits of Bulletproof Coffee and minimize the cons by eliminating the butter.

This, I’ve found, gives you the best of both worlds. You don’t break your fast, enhance your results, and don’t have any of the cons with the butter.

These are the C8-MCTs I mix in my morning coffee when fasting. Keto Elevate contains 100% pure C8-MCTs in a convenient powder form (no messy oils). It mixes easily into coffee and tastes just like a delicious coffee creamer. You can read more about it in my Keto Elevate review.

My Pick
BioTrust Keto Elevate

Support Many of the Keto Benefits Associated With Increased Ketones, & Support Them FAST, but Without the Difficulty of Doing Keto...

  • 3X Better Than Coconut Oil, Butter or MCTs
  • Heightened energy levels
  • Reduced cravings & appetite
  • Graceful aging
  • Healthy metabolism
  • Increased mental clarity & focus
  • Heightened physical performance and recovery

So at the end of the day, you can drink Bulletproof Coffee without it breaking your fast. Fasting isn’t like an on-and-off light switch, but there is some grey area that Bulletproof Coffee falls into. Since Bulletproof Coffee is all fat, it should raise your insulin and thus keep you more or less in a fasting mode.

It’ll be better for your weight loss to drink Bulletproof Coffee in the morning than to eat a sugary and high-carb breakfast like oatmeal with brown sugar. But Bulletproof Coffee isn’t ideal to drink since it’s high in saturated fats and calories. It can easily push you over the limit, depending on what you’re eating the rest of the day.

Plus, all the fats in Bulletproof Coffee can create too many ketones in your body and reduce the fat burning of your own fat stores. The trick is to get some ketones when fasting to help kickstart your body using its fat stores for fuel.

This is why I recommend forgoing the butter and instead just mixing C8-MCTs with your morning coffee when fasting. You’ll get the benefits of the coffee and MCTs without the negatives of the butter.

Your results will be better using this simpler combination, and will free up your allowance in the meals you eat during your feeding window.