Does MCT Oil Break a Fast? The Full Story, and How to Use It

Does MCT Oil Break a Fast

In the strictest sense, fasting means not eating anything at all. By that definition, anything you eat would break a fast.

But many of us do a type of “fasting” that allows certain supplements, and isn’t super strict. 

We still get a ton of health benefits from this modified fasting, and using a few supplements makes fasting a lot easier!

With that in mind…does MCT oil “break” a fast?

It all depends on how strict you want to be. And that depends on your goals.

Let’s dive into the details about MCT oil and see how it fits in with your goals.

What is MCT Oil?

The “MCT” in MCT oil stands for “medium chain triglyceride”.

Triglycerides are groups of three (hence “tri”) fatty acids that are connected to each other by a molecule called “glycerol”.  

They kind of look like little jellyfish, if the fatty acids were the jellyfish’s tentacles. 

medium chain triglyceride structure

The fatty acid “chains” in MCT oil are shorter than the ones you would find in most other fats (like butter or vegetable oil, for example).

They range from 6 to 12 carbon atoms in length (think back to chemistry class), and each one has a funny name:

  • 6 carbons: caproic acid
  • 8 carbons: caprylic acid
  • 10 carbons: capric acid
  • 12 carbons: lauric acid

Why does any of this matter?

Basically, the smaller fat particles in MCT oil are digested and absorbed more quickly than other fats. They’re also easier for your liver to make into ketones. (More about ketones below.)

Where Does MCT Oil Come From?

Coconut oil and palm oil are the main sources, each containing about 50% MCT oil.  

“Pure” MCT oil products that you can buy are usually made by concentrating the MCT’s in coconut oil.  

Interestingly, MCT’s also make up about 10% of the fat in milk from various animals (including cows), as well as human breast milk.

Will MCT Oil “Break” Your (Intermittent or Extended) Fast? 

You may be doing daily “intermittent” fasting, or multi-day “extended” fasting. Either way, the answer is basically the same:

Whether MCT oil ”breaks” your fast depends on how strict you are trying to be. And how strict you should be depends on your goals.

Let’s look at some examples.  

Will MCT Oil Prevent Weight Loss While Fasting?

When you fast, you mainly use your own body fat for energy (since there’s no other energy coming in). The longer you fast, the more fat burning ramps up.  

burning body fat while fasting graph chart 6 Sep 20

That’s why a lot of people fast to lose weight, or in other words to reduce body fat. 

Will MCT oil stop you from losing weight while fasting?

MCT oil has actually been shown to promote fat loss (more than other foods). But what about when you’re fasting?

As far as I know, there’s not any research on this specific question. But some basic reasoning applies:  

The more outside fat (such as MCT oil) you consume while fasting, the less fat from inside your body you’ll need to burn. And vice versa. 

Bottom line?

If your main goal is to reduce body fat while fasting, use the least amount of MCT oil possible. The more fat you consume, the less of your own body fat you will burn.

Does MCT Oil Raise Your Blood Sugar While Fasting?

When you fast, your blood sugar (glucose) level gradually goes down. That’s a good thing.

Some people use fasting as a tool to lower their blood sugar. It’s especially helpful for people with diabetes (or prediabetes), because their blood sugar levels tend to run too high. 

fasting lowers blood sugar graph

Will MCT oil raise your blood sugar while fasting?

In the one study I could find, MCT oil didn’t raise fasting blood sugar levels (but it did help diabetic patients process carbs more efficiently).

I’ve often used small amounts of MCT oil during extended fasts, and it doesn’t seem to affect my blood sugar either–it stays nice and low. 

Bottom Line?

If your main goal is to control blood sugar, using MCT oil while you fast is just fine.

Does MCT Oil Spike Insulin While Fasting?

Insulin is a hormone that pushes sugar into your fat cells and muscle cells after you eat.  

That’s why it’s sometimes called an “energy storage” hormone–it helps store the energy from your food inside your (growing) fat cells.

When you eat carbs, insulin goes up. When you don’t eat carbs, insulin goes down.

That’s why fasting and low-carb diets are good ways to lower insulin (and reduce body fat).  

graph of insulin going down while fasting

Will MCT oil raise your insulin level while fasting?

Probably not. The research suggests that MCT oil doesn’t affect fasting insulin levels, and actually improves insulin “sensitivity” (i.e it makes insulin work better in your body).  

Bottom line?

If your main goal is to lower your insulin level, using MCT oil while you fast is just fine. 

Does MCT Oil Stop Autophagy While Fasting?

Autophagy is when old worn-out proteins inside your cells get broken down and recycled.  

It’s a way to “clean out the trash”, so to speak, as well as a way to preserve and reuse protein in your body.

Will MCT oil prevent autophagy while fasting?

It hasn’t really been researched, so no one can say for sure. But most likely, the more MCT oil you consume, the less autophagy will be happening inside your body.

That’s because autophagy mainly happens when there’s not a lot of energy coming in (like when you’re fasting). So if you consume extra energy (in the form of MCT oil, for example), you’ll probably at least slow down autophagy, if not stop it completely.

Bottom line?

If your main goal is to stimulate autophagy, try to avoid eating anything while fasting. The extra food energy (i.e. calories) will probably decrease autophagy. 

Is MCT Oil Okay if I’m Fasting for Bowel Rest?

Basically anything you eat or drink (besides water) requires some amount of digestion.

As previously mentioned, MCT oil is easier to absorb than other types of fat. It also doesn’t require bile (from your gallbladder) or lipase (from your pancreas) for digestion, the way other fats do.

But even MCT oil requires some digestion.  

Bottom line?

MCT oil is pretty easy to digest. But if your main fasting goal is bowel rest, try to stick with just water as much as possible.

Bottom Line – Summary Chart

Here’s a checklist that summarizes whether MCT oil “breaks” a fast, depending on your specific goal(s).  

does MCT oil break a fast summary checklist chart

Other Health Benefits of MCT Oil

Besides helping lower body fat and improve insulin sensitivity (as mentioned above), MCT oil provides some other health benefits as well.

MCT Oil Increases Ketone Production

Ketones are the alternative energy source that your brain uses when you’re not eating carbs (like when you’re fasting, or eating a low carb, high fat “ketogenic” diet).

Consuming MCT oil increases your blood ketone levels.  

Why does this matter?

If you have more ketones, you’ll feel more energetic and focused, which means fasting will be easier!

For example, I often drink a little MCT oil on the first day or two of an extended fast, to give myself an energy boost while my body is still ramping up ketone production.

By the third or fourth day, my ketones are sky high and I have plenty of energy, so I stop the MCT oil.  

MCT oil features and benefits 6 Sep 20

This ketone-boosting effect is also a major reason why people put MCT oil in their “keto coffee” (aka Bulletproof Coffee).  

The Lauric Acid in MCT Oil Boosts the Immune System

Lauric acid (the longest fatty acid in MCT oil, with 12 carbons) appears to have some immune-boosting and antibacterial effects.

In other words, you’re probably less likely to get sick if you consume lauric acid.

Coconut oil is a great source of lauric acid, so there’s a strong case to be made for including coconut oil in your diet.

There is also a fair amount of lauric acid in breast milk, which is one reason breast milk helps protect babies from infections. (That’s reason number 1,037 why breast milk is great for babies!)

MCT Oil Helps Heal “Fatty Liver” Disease

“Fatty liver” means what it sounds like–excess fat deposits in the liver.  

Basically, your liver is a big grease ball. 🙂

This is usually the result of eating too much sugar or other processed carbs (like white bread, chips, crackers, sweets, and so on). There’s too much sugar for the liver to process, and the overflow turns into a million little globs of fat.

Almost 40%(!) of adults in the US now have fatty livers (thanks to our sugar-filled diet). It’s also a leading cause of liver failure (and you can’t live without a liver).

Why am I telling you this?

Because there is evidence that MCT oil helps heal fatty liver disease. So if your liver is gettin’ a little greasy, you may want to include some MCT oil in your diet (and cut back on the sugar while you’re at it). 

Fasting is also really good for fatty livers…more on that in a future post. 🙂

How to Use MCT Oil While Intermittent Fasting


Intermittent fasting (aka “time-restricted eating”) means eating all your food within a limited time each day, like 8 or 10 hours.  

For example, if you start eating at 10 am, and stop eating by 6 pm, that’s an 8-hour eating window.

Depending on your goals, it may be worthwhile to use MCT oil while intermittent fasting.

If you do, here are some ways you could go about it.

When to Take MCT Oil When Intermittent Fasting

Probably the most logical time to use MCT oil for time-restricted eating is a few hours before your first meal of the day.

For example, if you eat breakfast at 10 am, you could add some MCT oil to your “keto coffee” at 7 or 8 am to help curb any hunger you might otherwise feel in the morning.

Alternatively, you could take a little MCT oil in the evening, a couple hours after dinner. This could help boost your ketone levels through the night, which may improve your sleep quality.  

There’s really no “right way” to do it. Feel free to experiment and see what works the best for you.

How Much MCT Oil to Use When Intermittent Fasting

Like most things, how much MCT oil you should use depends on your goals.

In general, a couple tablespoons per day is a reasonable amount.

For example, you could use one tbsp in the morning (a couple hours before breakfast), and/or one tbsp in the evening (a couple hours after dinner).

You could also split it up into smaller but more frequent portions. 

how to use MCT oil for intermittent fasting

Like I said before, there’s not a one-size-fits-all approach that works for everyone.  

You may need to experiment to see how much MCT oil it takes to curb your hunger or boost your ketone levels. 

Ideally, try to use less MCT oil as time goes on. Remember – the more outside fat you consume, the less of your own body fat you’ll be burning.

Most of the time, I don’t even bother using MCT oil while intermittent fasting. My body is pretty well-adjusted, and I don’t really get hungry or low on energy.

If I do need a little boost, it doesn’t take that much MCT oil to do the trick–maybe about one teaspoon a couple times a day.

(Note: Some people get loose stools or stomach bloating when they take too much MCT oil, so that’s another reason not to overdo it.)

How to Use MCT Oil While Extended Fasting

 

MCT oil can also be a helpful tool during multi-day fasts.

Don’t go too crazy, because drinking a lot of MCT oil may reduce some of the health benefits you get from fasting (like fat burning or autophagy).

If you do decide to use it, here are some strategies you could try.

Getting a Smooth Start on a Long Fast

Unless you’ve been eating a pretty strict ketogenic diet (high fat, low carb), the first couple of days on a prolonged fast can be difficult.

That’s because it takes a couple days for your body to totally ramp-up fat burning and ketone production. Until then, you may feel a little sluggish.

(This is especially true when you’re a beginner, because your body’s not really used to using body fat for energy. It takes a few months to really build up the fat-burning “machinery”.)

How can you avoid this problem?

When you start a long fast, try taking some MCT oil on the first couple days (maybe 2-3 total tbsps per day), to boost your energy and ketone levels.

For example, I often include some MCT oil in whatever I’m drinking (usually bouillon) on day one or two of a longer fast.

After a couple days, I don’t bother with the MCT oil anymore because my ketones are high and I’m feeling pretty good. 

Fasting With Only MCT Oil

There’s a version of prolonged fasting called “fat fasting”, in which you eat nothing but fat (no protein or carbs). 

The idea is to continue taking in energy (in the form of fat), without raising your blood sugar or insulin levels–and without slowing down ketone production. 

Sometimes this is done with coconut oil, and called “coconut oil fasting”.   

For example, the first time I did an extended fast I ate a few tablespoons of coconut oil each day to keep my energy levels up. 

Coconut oil is about 50% MCT oil, but fasting with pure MCT oil may be even better.

That’s because concentrated MCT’s will raise your ketones even more than coconut oil, which can make you feel extra energetic and focused.

How can you actually use this?

If you find extended fasting difficult (or if you’ve never tried it before), go ahead and take a little MCT oil each day while you fast. 

For example, you could use one tbsp of MCT oil about three times per day–morning, afternoon, and evening.

how to use MCT oil for extended fasting

(Be aware – taking this much MCT oil could give you diarrhea, so be cautious.)

In general, try to use the least amount necessary to keep your energy up, and taper down over time.  

(Note:  There are other healthy “supplements” that may also be helpful for intermittent or extended fasting, such as apple cider vinegar and lemon water, for example.)

Conclusion – Final Thoughts 

If you’re ever wondering whether something breaks a fast…consider your goals.

Whether you should be using supplements, such as MCT oil, depends on what you’re trying to accomplish.

You can certainly use MCT oil while fasting and still get a lot of health benefits. For example, your blood sugar and insulin will come down, and your ketones will go up. These are all good things.

However, by consuming additional energy while you fast, you may prevent yourself from getting the maximum health benefits from fasting. 

For example, you probably won’t burn as much fat, stimulate as much autophagy, or rest your bowels as much if you consume MCT oil while you fast.

If you decide to use MCT oil as a tool to make fasting easier or more enjoyable, try not to overdo it. Use the least amount necessary to accomplish your goals (like controlling hunger, raising ketones, or maintaining energy).  

See if you can gradually decrease how much you use as time goes on. 

As your body adapts more and more, fasting will get easier, and you won’t need to rely on supplements like MCT oil as much.

So, does MCT oil break a fast? That answer depends on you.

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Ben Tanner, PA-C

Ben Tanner, PA-C

Ben has been practicing as a physician assistant (PA, or PA-C, similar to a doctor) in emergency medicine, urgent care, and family practice since 2014. Since 2016, he has developed an avid interest in various forms of fasting, using it to improve his own health while helping friends, family, and patients do the same.

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