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Does Bulletproof Coffee Break a Fast?

author avatar Dr. Eric Berg 08/31/2023

No, Bulletproof coffee doesn’t break your fast. In fact, it may promote ketosis and speed up fat burning!

Bulletproof coffee—also known as keto coffee—is a mixture of black coffee, medium-chain triglycerides, and unsalted butter. The fat content boosts ketone production but won’t impact your blood sugar and insulin levels, so your metabolism stays in a fasting state. 

Learn how to make Bulletproof coffee and discover why too much keto coffee may interfere with your weight loss goals.

Bulletproof coffee

What is Bulletproof coffee?

Bulletproof coffee is a delicious beverage that combines black coffee, unsalted butter, and medium-chain triglycerides (MCT). It’s essentially a more nutritious version of butter coffee, a traditional Asian high-fat coffee drink. 

Bulletproof coffee is carb-free and has no impact on blood sugar and insulin levels, which makes it a popular choice for people on a keto diet and those that practice intermittent fasting.  

Watch the video below to learn why bulletproof coffee won’t interfere with your intermittent fasting plan.

Why Bulletproof coffee is safe while fasting

Bulletproof coffee is a rich source of high-quality saturated fat and antioxidants. Regularly consuming keto coffee can help maintain energy levels, curb hunger, and extend your fasting period. 

Bulletproof coffee is safe during fasting. It doesn't contain carbs and won’t raise your blood sugar or insulin levels, keeping your metabolism in a natural fasting state.    

MCTs are saturated fatty acids that the liver rapidly converts into ketones, which are a by-product of fat metabolism and a readily available energy source. Because MCTs are converted to ketones, Bulletproof coffee promotes ketosis and may boost your energy.

Saturated fats in butter and ghee trigger the release of digestive enzymes and appetite-regulating hormones, which helps you feel satiated.

Research published in Fats and Satiety suggests that MCTs are the most satiating fatty acids, which explains why drinking Bulletproof coffee can help diminish hunger and extend your intermittent fasting window.

Coffee and coconut oil

Seven health benefits of bulletproof coffee

Bulletproof coffee is a rich source of healthy fats and antioxidants, which help improve physical performance and mental clarity, lower inflammation, and support metabolic health and hormonal balance. 

Here are seven reasons why you should drink Bulletproof coffee regularly!

1. Increased energy 

Not only does Bulletproof coffee contain caffeine which increases alertness, but it’s also a rich source of MCTs, which are rapidly digested and metabolized into large amounts of ketones, a highly efficient energy source for your cells.   

2. Cognitive health  

This large review published in BMC Geriatrics found that increasing the intake of medium-chain triglycerides supports mental clarity, cognitive function, and memory. 

Ketones are a preferred energy source for brain cells and increase the blood flow to brain tissue, which supports healthy oxygenation and nutrient exchange and enhances neural plasticity, the brain's natural ability to adjust and adapt.  

3. Anti-inflammatory  

Coffee beans are rich sources of antioxidants that help your body fight inflammation, explaining why regular coffee drinkers are at lower risk of inflammatory conditions, including metabolic syndrome, arthritis, or psoriasis. 

Coffee contains chlorogenic acid, a potent anti-inflammatory phytochemical that neutralizes harmful free radicals, which are metabolic by-products that can cause cellular damage and trigger inflammation.

4. Gallbladder health

Bulletproof coffee is an excellent beverage to stimulate bile flow and support gallbladder health. 

Both coffee and saturated fats trigger the secretion of cholecystokinin, a digestive hormone that stimulates gallbladder contraction and the release of bile into the small intestine. This supports gallbladder function and may lower the risk of bile sludge, a leading cause of gallstones.  

5. Keto-adaptation  

Drinking Bulletproof coffee promotes ketosis and can help you adapt to the metabolic changes of a ketogenic diet and intermittent fasting. 


Because Bulletproof coffee is carb-free, it won’t impact your blood sugar or insulin levels, keeping your metabolism in a fat-burning state.

In addition, MCTs are rapidly converted into ketones, which helps you reach ketosis faster and may speed up your cellular adaptation to using ketones as your primary fuel source.   

6. Liver health

Bulletproof coffee may be particularly beneficial for individuals with fatty liver disease

Coffee supports liver health by protecting liver cells from the detrimental effects of toxins and waste products the liver metabolizes and detoxifies. 

The International Journal of Molecular Sciences published research suggesting that MCTs help decrease liver fat, lower inflammation in liver cells, and reduce levels of harmful liver enzymes in people with cirrhosis.

7. Autophagy 

Bulletproof coffee is rich in health-promoting fats, which trigger the release of digestive enzymes and hormones that increase satiety and curb hunger. This can help significantly prolong your fasting periods.

Caloric restriction and extended fasting periods promote autophagy, your body’s natural ability to break down and recycle damaged cells and cellular components. 

Joshua Rabinowitz and Eileen While, research scientists and authors of Autophagy and Metabolism, explain, “Autophagy preserves the health of cells and tissues by replacing outdated and damaged cellular components with fresh ones. In starvation, it provides an internal source of nutrients for energy generation and, thus, survival.”

Autophagy is an essential biochemical mechanism that promotes cellular health, prevents disease, and promotes longevity.   

Young woman holding scale

Can Bulletproof coffee slow down weight loss?

“Bulletproof coffee won’t break your fast,” says Dr. Berg, “but drinking too much can slow down your weight loss.”

Depending on the recipe and serving size, a single cup of Bulletproof coffee can contain almost 60 percent of your daily fat requirements. 

The liver prioritizes the breakdown of dietary fats before stored body fat. Drinking Bulletproof coffee may shift your metabolism away from burning stored body fat as an energy source and hinder weight loss. 

If you suspect Bulletproof coffee may interfere with your weight loss goals, adjust the serving size and recipe to reduce your fat intake to promote the breakdown of stored fat.  

Easy Bulletproof coffee recipe

Making Bulletproof coffee is simple and takes just a few minutes! Here’s how. 


  • 1 cup freshly brewed coffee 

  • 1 to 2 Tbsp grass-fed, unsalted butter or grass-fed ghee 

  • 1 to 2 Tbsp MCT oil 



  1. Use a blender to combine all ingredients for 20 to 30 seconds or until mixture has the consistency of a creamy latte.

  2. Bulletproof coffee can be served warm or iced and topped with cinnamon, nutmeg, or Himalayan salt.   

Bulletproof coffee ingredients

Key takeaways

Bulletproof coffee is a keto-friendly high-fat coffee drink that delivers an energy boost without breaking your fast. 

This creamy beverage is rich in high-quality fats and carb-free, helps you feel satiated, and keeps your body in fat-burning mode. 

However, Bulletproof coffee can deliver as much as 60 percent of your daily fat requirements, and drinking too much may block your metabolism from tapping into stored body fat, potentially slowing down weight loss. 


1. Can I have Bulletproof coffee while doing intermittent fasting?

Yes, Bulletproof coffee is safe when fasting. It’s carb-free and won’t impact your blood sugar or insulin levels, which keeps your body in a fasted state. 


2. Does MCT oil in coffee break a fast?

No, medium-chain triglyceride oil in coffee doesn’t break a fast. These medium-chain fatty acids don’t raise blood glucose or insulin levels, keeping your body in its natural fasting state.  

3. Does Bulletproof coffee with coconut oil break a fast?

Drinking Bulletproof coffee with coconut oil won’t break your fast. Coconut oil is a rich MCT source that doesn’t impact blood sugar or insulin levels, keeping your metabolism in ketosis and not breaking your fast.   

4. What can I put in my coffee that won't break my fast?

To not disrupt your fasting state, it’s essential to only add ingredients to your coffee that won’t raise your blood sugar or insulin levels. 

Butter or ghee rich in saturated fats and MCTs such as coconut oil won’t raise insulin and keep your metabolism in fat-burning mode. You can add nutmeg, cinnamon, and sea salt—these spices won’t break an intermittent fast.

5. Can I have Bulletproof coffee during intermittent fasting?

Yes, you can drink coffee during intermittent fasting. Bulletproof coffee is carb-free and won’t impact your blood sugar or insulin levels, which maintains ketosis and keeps your metabolism in a fasting state. 


6. How long can you fast on Bulletproof coffee?

How long you can fast on Bulletproof coffee depends on how well your body is adapted to intermittent fasting and your general fasting routine. 

Bulletproof coffee is a rich source of healthy fats which make you feel satiated and promote the production of ketones which helps to extend fasting periods. 


7. How much Bulletproof coffee can I have while fasting?

Bulletproof coffee is a high-fat coffee beverage with a high-calorie content. Consuming more than one cup of Bulletproof coffee daily isn’t recommended. More can quickly exceed your calorie and fat requirements, slowing weight loss or leading to weight gain. 


8. Can Bulletproof coffee slow down weight loss?

Yes, Bulletproof coffee can slow down weight loss in some people. It’s a high-fat coffee drink, and one cup may provide as much as 60 percent of your daily fat requirements. 

Your liver prioritizes the metabolism of dietary fats, and drinking Bulletproof coffee can prevent the breakdown of stored body fat for energy and hinder weight loss.


9. How much Bulletproof coffee is too much?

How much Bulletproof coffee is too much depends on your overall diet, body composition, fat requirements, and activity levels. 

Bulletproof coffee is a high-fat coffee drink, and it’s generally recommended not to exceed one cup daily to avoid excessive fat and calorie intake.

10. How do I make Bulletproof coffee?

Making Bulletproof coffee is easy. Blend one cup of freshly brewed coffee with one to two tablespoons of unsalted butter and one to two tablespoons of MCT oil until creamy.

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