Are you worried that adding things to your coffee will break your intermittent fast?

Your worries are over!

We stuck our finger 16 times over a 4-day period to bring YOU a definitive answer about how your body handles black coffee, cream, MCT Oil, and butter.

Let’s figure out once and for all if these additions to your morning coffee will break your fast!

What Coffee Additive Breaks My Intermittent Fast? Cream, MCT Oil, or Butter [Video]

In this video we’ll answer…

Does black coffee break my fast?

Can I have cream in my coffee when I’m intermittent fasting?

Can I have MCT oil in my coffee and not break my fast?

Will butter in my coffee break my intermittent fast?

Here’s How We Tested Coffee and Intermittent Fasting

Doctor Keith and I are both science geeks at heart, so we decided to follow the scientific method.

This means we started with a hypothesis, decided how to test that hypothesis, gathered our results, and came to our conclusions.

Day 1: Testing Black Coffee

Hypothesis

Our first hypothesis was mostly a control to see what happened to our ketones and glucose levels when we drank 16 ounces of black coffee.

We hypothesized that if we drink 16 ounces of coffee while intermittent fasting, it will NOT knock us out of ketosis or spike our blood glucose.

Materials and Methods

The materials we used were:

Precision Xtra ketone and glucose meter, which you can get on Amazon. Ketone and glucose strips 16 ounces of black coffee

We followed a 16:8 Intermittent fasting schedule. This means we stopped eating by 8 pm the night before the tests and did not plan to start eating until 12 pm on the day of the tests.

We performed the test over a period of two hours.

We started by taking an initial reading at 0 minutes. We then tested again at 30, 60, and 120 minutes.

During that time, we did not exercise or consume any supplements.

To make sure we stayed consistent with how we drank coffee, we decided to drink 8 ounces of black coffee in the first 30 minutes, and the other 8 ounces in the next half hour.

Results

Becky’s ketone level results:

As you can see from these results, Becky’s ketone level after drinking black coffee went up, showing that she was deeper into ketosis.

Keith’s ketone level results:

Keith’s ketone levels went down by only 0.1 mmol/L.

Becky’s blood glucose results:

Becky’s glucose readings for black coffee started low and stayed low.

Keith’s blood glucose results:

Keith’s glucose readings started somewhat high (which is normal for him) and then went down.

Day one of pricking our fingers was done, and our hypothesis was accepted!

Black Coffee Conclusion: Drinking Black Coffee while Intermittent Fasting will NOT break your fast or knock you out of ketosis.

Day 2: Testing Cream in Coffee

Hypothesis

We hypothesized that if we drink 16 ounces of coffee with heavy cream while intermittent fasting, it will NOT knock us out of ketosis or spike our blood glucose.

Materials and Methods

We used the same materials and methods as before, only this time we added 2 tablespoons of heavy (whipping) cream to each of our 16 ounces of coffee.

Results

Becky’s ketone level results:

As you can see from these results, Becky’s ketones started at 1.8 and rose to 2.1 mmol/L.

Keith’s ketone level results:

Keith’s ketones started at .2 and went up to .3 mmol/L

Becky’s blood glucose results:

Becky’s blood glucose dropped by 10 points over the 120 Minutes.

Keith’s blood glucose results:

Keith’s blood glucose went up at first but then settled down after 120 minutes to return to very near the initial level.

Day two of pricking our fingers was done, and our hypothesis was accepted!

Coffee with Cream Conclusion: Drinking Coffee with Heavy Cream while Intermittent Fasting will NOT break your fast or knock you out of ketosis.

Are you looking for a place to start your low carb/keto journey? Get free access to our list of 100 Low Carb Foods here!

Day 3: Testing MCT Oil in Coffee

Hypothesis

We hypothesized that if we drink 16 ounces of coffee with MCT Oil while intermittent fasting, it will NOT knock us out of ketosis or spike our blood glucose.

Materials and Methods

We continued to follow the same methods as our previous days of testing, but on this day, we put 1 tablespoon of MCT oil in 16 ounces of coffee.

Results

The results were surprising!

Becky’s ketone level results:

Becky’s ketones rose from 2.3 to 3.2 mmol/L.

Keith’s ketone level results:

Keith’s ketones started at .5 and went up to .8 mmol/L. However, take notice that there was a peak of 1.3 mmol/L at 60 minutes.

Becky’s blood glucose results:

Becky’s glucose reading dropped by 9 points.

Keith’s blood glucose results:

Keith’s glucose reading dropped by 7 points

Day three of pricking our fingers was done, and our hypothesis was once again accepted!

MCT Oil was interesting! We both experienced a rise in ketones and drop in blood glucose readings after 120 minutes when we consumed MCT oil. That is the desired result!

Coffee with MCT Oil Conclusion: Drinking Coffee with MCT Oil while Intermittent Fasting will NOT break your fast or knock you out of ketosis. In fact, MCT Oil will increase ketones and lower blood glucose.

Click here to check out another experiment we did, where we tested whether or not MCT Oil as a supplement will accelerate fat loss.

Day 4: Testing Butter in Coffee

Hypothesis

We hypothesized that if we drink 16 ounces of coffee with butter while intermittent fasting, it will NOT knock us out of ketosis or spike our glucose.

Materials and Methods

We used the same methods that we had been using all week, but this time we put 2 tablespoons of Kerry Gold butter in our 16-ounce coffees.

Results

Becky’s ketone level results:

After drinking coffee with butter, Becky’s ketones rose from 2.1 to 2.6 mmol/L.

Keith’s ketone level results:

Keith’s Ketones started at 0.5 and rose to 0.6 mmol/L.

Becky’s blood glucose level results:

Becky’s glucose level dropped by 6 points.

Keith’s blood glucose level results:

Keith’s Glucose level dropped by 13 points.

Day four of pricking our fingers was done, and our hypothesis was again accepted!

Coffee with Butter Conclusion: Drinking Coffee with Butter while Intermittent Fasting will NOT break your fast or knock you out of ketosis.

Discussion of Results Regarding Coffee and Intermittent Fasting

While this was a small study, our results show the following:

None of the coffee additives caused a spike in our blood glucose levels. In fact, they were more likely to lower our blood glucose levels. After 120 minutes, our blood glucose levels dropped on all four days. In other words, drinking black coffee as well as coffee with cream, MCT oil, or butter lowered our blood glucose. None of the coffee additives caused a significant drop in our blood ketone levels. At 120 minutes, my, (Becky’s), ketone readings increased after drinking black coffee, coffee with cream, coffee with MCT oil, and coffee with butter. At 120 minutes, Keith’s ketone readings dropped by 0.1 mmol/L after drinking only black coffee. His ketone readings rose slightly after consuming coffee with cream, MCT oil, and butter. MCT oil caused an impressive rise in blood ketone levels and a drop in blood glucose for Becky and Keith.

Conclusion: Coffee and Intermittent Fasting

Since there was an overall drop in our blood glucose readings and no significant drop in ketone readings, we conclude that…

Adding Cream, MCT Oil, or Butter to coffee does NOT break your intermittent fast.

Since MCT Oil significantly increased our blood ketone readings, we can also conclude that…

If you are following a ketogenic diet, MCT Oil is beneficial to add to your coffee while intermittent fasting.

Want to get started on your own low carb/keto journey just like Dr. Keith did? Sign-up below to get free access to our list of 100 Low Carb Foods.

What Breaks a Fast? Our Test

About the Author

Dr. Becky Gillaspy, DC graduated Summa Cum Laude with research honors from Palmer College of Chiropractic in 1991.