Does Coffee Break Your Fast?

You wake up on day 1 of your fast, pour yourself a steaming cup of coffee, bring it to your lips, and then, just as you’re about to take a sip… oh wait: “Am I allowed to have this?” It smells soooo good, but will it derail your fast?

Probably not. But it depends on your goals.

Most people fast for one of three reasons: weight loss/metabolic health, gut rest, or longevity. Whether coffee breaks your fast depends on why you’re fasting. It also depends on how you drink your coffee. Do you take it black? With cream? With butter? So let’s pour our coffee talk through that filter.

Black Coffee

Coffee itself has almost no calories, so it already has that going for it. Several studies have examined whether fasting still demonstrates health and disease-prevention benefits if the people fasting drink coffee. The answer: yep! The benefits are intact. These studies also considered whether people got those same benefits from a restricted calorie fast (RCF) accounting for less than 25% of energy needs, and saw the same result.

One literature review demonstrated that coffee was associated with a decrease in insulin sensitivity, but scientists have observed those same short-term effects in fasting in general, with or without coffee. During nutrient deprivation, cells become slightly more insulin resistant likely due to the body prioritizing fuel to go to the brain instead of other cells in the body. This was also a short-term study, so further research would be necessary to show whether coffee has any detrimental effects on insulin sensitivity in the long term. Conversely, there have been many long-term studies linking regular coffee consumption to positive health benefits including reducing the risk of type 2 diabetes.

Another study showed that consumption of both caffeinated and decaffeinated coffee trigger autophagy in mice, which is good news for longevity. The authors of this study related the increase in mTOR inhibition and other cellular processes to the polyphenols in coffee. This same study hasn’t been replicated in humans yet, so we have to take these results with a hefty grain of Himalayan sea salt.

What if you’re fasting for gut rest? Even though black coffee has negligible calories, it does trigger some digestive functions. Coffee stimulates gastrin (a hormone that triggers the secretion of gastric acid) and gallbladder contraction, both of which have an impact on our gastrointestinal tract. Coffee intake may also elicit a reflux sensation, which isn’t ideal for those with heartburn issues.

The Verdict:

  • Fasting for metabolic health/weight loss: likely does not break a fast
  • Fasting for gut rest: does break a fast
  • Fasting for longevity: likely does not break a fast

Butter (Bulletproof) Coffee

Butter coffee, popularized by the bulletproof coffee brand, typically has added butter and/or medium chain triglyceride (MCT) oil. Even though MCT oil is calorically dense, it’s been shown to improve insulin-mediated glucose metabolism. Plus, the body easily converts MCTs into ketones to use for energy. Doctors have also used MCT oil to induce ketosis in the management of epilepsy, demonstrating that the consumption of MCT oil can still produce a ketogenic environment.

Butter and MCT oils have a different chemical composition though. MCTs are produced from coconut oil and, as the name suggests, are 100% made-up of medium-chain triglycerides. Butter, on the other hand, is mostly composed of long chain triglycerides (LCTs). MCTs and LCTs have a different effect on our gastrointestinal system. MCTs are absorbed directly through the portal vein and taken immediately to the liver, whereas LCTs stimulate pancreatic enzymes and require the release of bile into the GI tract. So, butter does trigger some digestive processes while MCTs are less likely to do so.

Butter also has a small amount of protein in it. Typically, protein inhibits autophagy, but butter contains such a small amount it’s unlikely to matter. MCT oil contains no protein at all, but it is highly caloric. Energy restriction is also important for autophagy, so overconsumption of butter or MCTs may not provide the low nutrient environment necessary for autophagy’s longevity benefits. For example, a typical bulletproof coffee calls for 2 Tbsp. butter and 1 Tbsp. MCT oil, which provides ~320 kcal. It’s possible that this amount of energy intake either slows or stops the longevity benefits of fasting.

The Verdict:

  • Fasting for metabolic health/weight loss: likely does not break a fast
  • Fasting for gut rest: though MCT oil has minimal impact on the digestion, coffee and butter break a fast focused on gut rest
  • Fasting for longevity: likely breaks a fast

Coffee + Cream

Plain, high-quality dairy by itself likely does not contribute to weight gain or increased risk of metabolic disease. One study was even able to show an association between consumption of trans-palmitoleate (a fat found in milk) and lower fasting insulin levels. However, quantity is key since a couple Tbsp. of cream/milk in coffee is very different than a few cups.

Cream, milk, and other dairy products contain carbohydrates, protein, and fat that do require digestion, so the gut is activated after consumption. Research is limited on dairy and its role in autophagy, but a few studies have shown that high-quality dairy consumption does not increase risk of chronic disease.

The Verdict:

  • Fasting for metabolic health/weight loss: likely does not break a fast in small quantities
  • Fasting for gut rest: breaks a fast
  • Fasting for longevity: likely does not break a fast, but research is limited in this area

98 comments on “Does Coffee Break Your Fast?

  • I have read so many studies about adding Stevia to your coffee or tea could you advise if drinking black coffee or tea with a package of stevia will break a fast?

  • Thank you for dividing the purposes for fasting into three distinct categories. The answer is, it depends. That answers a lot of questions for me.

  • I wanna ask about coffee which is prepared by Almond milk, does it break my fasting? ( weight loss and metabolic health)

  • Hi!
    If I drink my coffee with half cup of unsweetened almond milk (very low carb, less then 1G and only 15 calories) so it will break my fast of ” gut rest”?

  • The way you’ve described coffee with cream (i.e. ~2Tbsp.) would suggest that it doesn’t cover milk-based coffee styles that we drink a lot of here in Australia, e.g. cafe latte, cappuccino, flat white — each contains a high ratio of milk to water. Would it be to correct to assume that a standard latte of ~220mL — of which at least two thirds is milk — would break a fast for metabolic health/weight loss reasons?

    • I think about it as breaking my fast. Really any calorie macro rich and or something that will spike my insulin I stay away from. Break down the drink you just described and look at it as multiple parts. In the recipe I read on how to make a latte it said about 6 oz of milk for every shot of espresso. So lets say you have 2 shots and 12 oz of milk. 18 calories an oz is 216 calories. Would you drink 12oz of milk during your fasting window? I do IF for the added benefits of autophagy ,mTOR, increased cardiovascular performance, be more insulin resistant, and I also think it helps me think about what I put in my body.

  • Currently drinking my long black 😻

    Thank you for providing this informational piece – I notice myself when I consume too much coffee there is an acid reflux evident.

    Heres to longevity! 🙏

  • Hi, can i eat any kind of foods after intermittent fasting?

    Or do i need to watch calories and strict on diet after i finish the intermittent fasting?

    Because i have no idea on what to eat after my intermittent fasting like 20:4

  • I would like to see soy and almond creamer added to that list to know what type of impact it has along with my morning coffee.

    • Depends on the sugar/carbs in those milks. Look at the label. The point is to stay away from carbs when fasting because carbs/sugar trigger the release of insulin

  • Great article and helpful but somewhat left me wanting more

    Gut rest of metabolic-rest fasts are pretty much the same thing – I am unsure it addresses the coffee breaking of tyebfast I would have preferred, especially when the verdict is ‘likely’…

    It would be helpful to have one on Tea and different types of.

  • Hello,
    Thanks for the great efforts you have done to ease my concerns.
    I agree with you about black coffee, it really doesn’t break the fast. But bulletproof coffee and cream coffee have complex compounds require more insulin.

  • Thanks for the article. May I ask an off topic question, I’m not sure where to ask it so sorry in advance? Is there any proven benefit/difference between the different fasts explained here and some religious fasts where you’re not allowed to eat nor *drink* anything from dawn to dusk?

    I have read around but people usually don’t mean complete abstinence when they talk about fasting so it’s hard to find an answer. Is depriving the body of liquids as well as food any good/better?

    Thank you very much.

  • This is very helpful. I try to do 22/2 fasting daily but I still have my morning coffee with MCT in it hoping it doesn’t break my fast (weight loss being the goal for me). Very happy to know it’s unlikely to 🙌🏻

  • I’ve listened to this topic be explained 4-5 times by scientists and doctors but this is bar far the clearest and most useful information I’ve seen.

  • Awesome post. I fast 18hrs in a row. Most days. The occasional black coffee gets me through! My strength and nutrition coach has already told me this. It’s nice to have it reconfirmed! Thx!

  • Hi!
    Great news. But, what about Tea drinkers? I am particularly partial to black tea with 3 spoonfulls of low fat milk + sucralose (and I’m going for weight loss).
    Thank you

  • This was a great article. I’m curious where the Laird Superfood creamers would fall. Based on the ingredients, do you think they would fall in a similar category as the butter coffee?

    Thank you

  • Thank you for this! I started the circadian fast yesterday and was just wondering if coffee had any effect. I normally take it with a tbsp or two of half & half. Since I’m fasting for metabolic/weight loss reasons, I can have that cup of coffee for when I have to be at work at 5 in the morning. 🙂

  • Great info! I like that the article addresses the different “genres” of coffee and how they impact different fasting goals. Thank you!!!

    Will you do something similar for HMB to eliminate catabolism whole exercising in a fasting state?

  • I don’t understand why mct oil would break a fast (for autophagy/longevity) but cream would not. Is it the calories? What about coffee with 1-2 teaspoons of mct oil (much less than the amount you list)? Would this limit autophagy? That is my main reason for fasting. Thank you.

  • I fast 18-20 hrs per day for autophagy and long term health (ie. Prevent diabetes, dementia, Alzheimer’s, any neurological disease). I’ve learned that a “clean fast” means not releasing insulin during the fast! Is this correct?

  • I drink coffee every morning. I drink 2-3 cups of coffee with 2% milk and truvia sweetener.

    I love to fast. I have lost 60lbs and I am determined to keep it off.

    I believe fasting will be the tool along with portion control as well as exercise (walking) 8K daily—-will enable me to maintain my weight loss.

  • I’m extremely glad to see this new article!! I have been wondering about this, as coffee w a small amount of milk is the only break in my fast each day. I have also bern wondering if 1 diet coke (I know..chemicals!) 🙂 can make a negative difference in my fasts.

    Would also be very interested to hear how to get through a tough weight plateau. I perform various hours of fasting daily w 16-21 hour fasts during the work week and 13-15 hour fasts on the weekends. And I do a strong weight/floor/cardio program 3 days weekly, but my weight is the same for 2 months!! Very frustrating! Thank you so much. Lucy Poole, San Francisco, CA

  • Thank you for this article! This app has been so helpful just as a way to keep me honest about when I start and stop putting things in my mouth. The addition of helpful information makes Zero even better.

  • I think this is the primary discussion when it comes to fasting! 20 something years ago, during my bodybuilding days, I did my cardio in a fasted state first thing in the morning but would always drink black coffee before heading out.

  • Excellent info. Always has been my question. I use 36% Avalon dairy whipping cream in my coffee. 1-2 Tablespoons per 8 oz cup. Sometimes black.
    Thanks love this app and all the improvements.

  • I also agree with your findings, for me a 18+ hour fast is just easier than bringing a lunch to work.

    Anyway I have coffee in the morning which also helps curb hunger. Question is I do 18:6 up to a 23 hour one (dinner to dinner), for my gut while my black coffee breaks my fast, how long until it “resets” assuming no other intake. Do I lose an hour of my fast? Or is it just like I ate food?

  • I was interested as soon as I saw this post in my notifications, but already concluded I would continue drinking coffee even if the article concluded coffee breaks a fast.

    Truth is, technically it does break a fast. Your body must metabolize it, simply put. Am I going to stop drinking coffee, no. Will I continue to 16:8 fast, yes.

  • Can we please post the sources for the articles? That would be great. As I forward these out to people to try to encourage them to fast they like to challenge data so providing sources helps with that effort. Thank you

  • I think you were reading my mind, I’ve been wondering about coffee! Especially with a little milk or cream (i’ll pass on the butter🤭) Great knowing coffee + cream is generally OK for both metabolic & longevity fasting; I’ll look into herbal “coffee” or tea for gut rest. thank you so much for this article.

  • I fasted for over a year (for weight loss) and have had coffee and cream throughout, every day. In fact that’s what has helped me. I’ve lost 22kg and I’m now back to my ‘fighting fit’ weight when I was in the Army in my early 20s.

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