Does Coffee Break a Fast? Unveiling the Fasting-Coffee Conundrum

Embarking on the journey of intermittent fasting brings forth numerous queries, chiefly around the morning brew ritual. Does drinking coffee break a fast, or could it possibly be a trusty companion in your fasting voyage?

Will coffee break my fast or support my metabolic endeavours? The query, ‘Will drinking coffee break my fast?’ is often the first question that arises in our Data-Driven Fasting Challenges.

This comprehensive guide explores the coffee-fasting interplay, shedding light on how coffee, when intertwined with fasting, influences your blood sugar, insulin levels, and, ultimately, your fasting goals.

Does Coffee Break Your Fast?

To get to the punch line first:

  • So long as you’re not adding hundreds of calories worth of milk, butter, cream, sugar, or MCT oil, your morning cuppa doesn’t count as a meal. 
  • If you are using your blood sugar to guide your meal timing and choices as we do in Data-Driven Fasting, you don’t need to test your blood glucose before or after coffee.
Does Coffee Break Your Fast?

While there is plenty of debate over whether coffee or artificial sweeteners will break your fast, you need to find the balance between what is optimal, enjoyable, and, most importantly, sustainable for you

While becoming a monk and drinking filtered water may be a ‘better’ choice, doing a complete 180 and axing caffeine overnight might not leave you feeling so great. 

Because we develop a tolerance to caffeine, many people will get a headache if they suddenly slash their intake.  Thus, if you choose to cut back on your caffeine, it’s best to scale back slowly.

Most studies find caffeine can be beneficial.  Caffeine can stimulate metabolic rate and fat loss and prompt the release of stored energy from the liver.  Because of its role as a stimulant, it can also help to blunt appetite.

But caffeine isn’t always a ‘yes’.  For example, if you’re not sleeping well because you are drinking too much coffee too late in the day, you should stop earlier or reduce your intake.  Similarly, if you find yourself craving it and unable to function without it, it might be worth considering how much Java you’re guzzling. 

Will Coffee Break My Fast? 

Considering the goal of Data-Driven Fasting is for you to achieve a long-term negative energy balance, the slight rise in glucose around your coffee should not be a concern as long as your coffee contains minimal energy. 

Caffeine tends to trigger the release of stress hormones like cortisol.  This is why some people experience ‘the jitters’ when drinking it.  With the release of cortisol, stored glucose in the form of liver glycogen is released into the bloodstream, which may register on your meter as slightly elevated blood sugars.

While the bump in glucose could be a surprise, considering that black coffee is ‘zero-calorie’, it’s probably nothing to be worried about.  Thus, any change in insulin or blood sugar around your coffee in the morning won’t impact fat loss if it doesn’t provide significant energy.  Your short-term bump in insulin and the release of stored glucose will balance out across the day. 

But suppose it contains calories (e.g., milk, sugar, chocolate powder, or MCT oil)?  In that case, your body will switch from burning body fat to burning the energy you just consumed from whatever coffee conglomerate you conjured up this morning. 

We generally find people do best in terms of satiety and blood sugar stability when their first meal involves a solid dose of protein.  So, if your first meal for the day is 500 calories from a bulletproof coffee or a coffee milkshake from Starbucks, you’ll probably be better off switching to black coffee or dialling it back to a small dash of cream with some stevia. 

Instead of wondering, ‘Will this break my fast?’, try asking yourself, ‘Will this keep me in a negative energy balance so I can lower my blood glucose and burn fat?’

What Is Fasting?

If you’re entirely new to nutrition, you might wonder, ‘What is this fasting everyone is speaking of?’

So, let’s start from the beginning!

Simply put, ‘fasting’ is (intentionally or unintentionally) refraining from eating.

Unless you wake up every hour and sleepwalk to the fridge, you are innately fasting every night when you forego food during your slumber.  When you’re in between meals, you’re technically fasting.  Essentially, you’re fasting whenever you’re not shovelling food into your mouth.

Fasting isn’t anything new; it’s been used for religious purposes for thousands of years.

  • Jesus fasted for forty days and forty nights (Matthew 4:2). 
  • Orthodox Christians fast for portions of this same period, which we know today as Lent. 
  • Muslims do not eat during daylight hours for the month of Ramadan. 
  • Buddhists regularly fast from noon to dawn the following day (similar to an 18:6 fast).
  • Jews fast for Tisha b’Av and Yom Kippur.  

Many of us are accustomed to constantly eating, from the moment we wake up to just before bed.  Hence, an hour or two without food in the modern day could be considered a fast or abstaining from eating.

Many believe that fasting duration and the benefits of fasting are positively correlated.  In other words, fasting for longer is simply better.  However, this way of thinking is not necessarily accurate.  Moreover, this ‘longer is better’ mentality often comes with a downside of poorer food choices when we eat again and a dysregulated appetite in the days and weeks.  

No matter the situation, fasting is considered a stressor.  Without food, the body perceives starvation and releases stress hormones.  This can contribute to poor sleep, cravings, mood swings, and weight gain.  It can also push the body to break down its precious metabolically active lean mass (muscle) for fuel, thus lowering your metabolic rate. 

Intelligent fasting undoubtedly has an extensive list of benefits.  However, sustainable metabolic health improvements come once we find a way to eat that allows us to improve our body composition: losing fat and gaining muscle. 

Energy toxicity—not insulin toxicity—is the root cause of most modern diseases.  Hence, fasting unloads this extra energy and is beneficial. 

But rather than simply thinking ‘longer is better,’ you must apply the minimum effective dose of fasting or the minimum duration you can use while still seeing results, and you must get the nutrients you need when you eat again.

Will Coffee Raise My Blood Sugar and Insulin? 

Some people find their blood glucose levels rise when drinking their coffee and wonder if it’s causing an insulin response. 

Because the caffeine in coffee triggers the release of adrenaline and cortisol, it causes the body to release stored energy into the bloodstream.  However, coffee alone does not provide significant calories, so it will not cause insulin to rise significantly over the long term. 

Some people who test their blood glucose in the morning around their regular cuppa see their blood glucose rise.  However, it’s difficult to discern whether this is due to the dawn phenomenon — your body’s innate morning circadian rhythm of releasing stress hormones and stored liver glycogen to boot up your system — or the coffee itself. 

If you want to find out whether coffee is spiking your blood glucose, you could test your blood sugar before and after consuming caffeinated coffee, decaffeinated coffee, and water at the same time of day over the course of several mornings.  If you see a similar response at the same time regardless of what you drank, it’s likely the dawn phenomenon rather than the coffee. 

What Are the Benefits of Coffee for Metabolism and Weight Loss?

Because coffee contains concentrated amounts of the stimulating compound caffeine, it’s used in many overpriced ‘fat-burning’ supplements and is advertised as a ‘fat burner’. 

caffeine supplements to temporarily boost your metabolism

Stimulants increase the body’s metabolic rate, which you may experience as an increased pulse, more energy, sweating, and (sometimes) higher blood pressure.  Performing more work pushes the body to burn more calories, which can help you lose weight. 

Of course, if you overdo this, especially too close to bedtime, your sleep will suffer and you’ll need more stimulants the next day to get you going.  So, you need to find a balance that works for the long term. 

What Are the Other Benefits of Coffee? 

There’s more to coffee than just a tasty caffeine delivery vehicle.  Aside from its fat-burning effects, coffee has several other health benefits worth learning about.

For starters, coffee is loaded with polyphenols, which are plant compounds known for their antioxidant effects.  Antioxidants protect the body from oxidative stress or damage from substances that are harmful to the body.

Coffee also works as a nootropic, or mind function enhancer, and can thus give you a cognitive kick.

Coffee’s bitter taste is not only delicious but can also stimulate the release of digestive juices like bile and improve liver performance.  Bile is the substance our bodies use to break down fats, and compounds in coffee can speed up the liver’s ability to function.

Finally, coffee’s role as a stimulant can reduce appetite and help someone control their cravings.  While coffee may stimulate your metabolism in the short term and raise your blood sugars a little, it also has been shown to lower blood sugar in the long term

Are There Any Downsides to Drinking Coffee?

The ‘functional nutrition’ world seems to be at war over coffee.  For many, this beverage is relatively harmless.  But for others, it doesn’t always sit well! 

Coffee is relatively acidic.  If someone has gastrointestinal problems or a sensitive stomach, it might exacerbate or worsen their situation.

How coffee is grown and processed can make or break the quality of the product.  Many run-of-the-mill brands have been found to be loaded with pesticides like glyphosate, which has been linked to intestinal permeability (‘leaky gut’), autoimmunity, autism, cancer, and Type 2 diabetes.

Because of the roasting and storage process, coffee is predisposed to becoming mouldy.  Thus, coffee has also been shown to contain mould, which could transfer to you.  Mould and the toxins it produces have been linked to cancer, autoimmunity, mood disorders, allergies, and GI problems, amongst other things.

To counter some of these adverse effects, you can try an organic, certified mould-free, fair-trade brand.  If you find you get phlegmy or don’t feel too well after coffee, this change might make your morning cuppa a bit more enjoyable!

When Should I Not Drink Coffee?

Coffee is safe for just about everyone. 

Coffee is one of the most widely consumed beverages in the world.  In 2020/2021, around 166 million 60-kilogram bags of coffee were consumed worldwide.  

But if you have a pre-existing condition, switching to a different beverage might be worthwhile.

If you have high blood pressure, you may have heard that coffee could continue to increase it.  If this applies to you, paying attention to your numbers might do you well when you’re ordering your morning Starbucks.

For someone with ‘adrenal fatigue’, it might be worth swapping out your black coffee for herbal tea.  Adrenal imbalances usually occur from large amounts of stress that stimulate the adrenals to produce excessive levels of stress hormones for long periods. 

Over time, the adrenals cannot produce enough stress hormones to match their demand and become ‘fatigued’.  The caffeine may allow you to push for longer without taking a rest, thus leading to a bigger crash once you finally stop. 

Because coffee stimulates the release of stress hormones like cortisol, drinking a cup of coffee might exacerbate this.  If this is the case for you, you might find yourself moving slowly in the morning, unable to function without caffeine, wired at night, having energy slumps in the middle of the day, and feeling relatively fatigued.

Lastly, certain medications are known to interact with coffee and should be taken with care alongside that Americano of yours!

What Can I Put in My Coffee That Won’t Break My Fast?

We get a lot of questions in our Data-Driven Fasting Challenges about what people can (or can’t) put in their coffee without breaking their fast.   

Does Black Coffee Break a Fast?

No.  It is a zero-calorie beverage that will not break your fast if it is genuinely black coffee or coffee sans add-ins made with pure water.  It may, however, alter your blood sugar or insulin levels in the short term, but this is generally not something to be concerned about for most people.

Does Black Coffee Kick Me Out of Ketosis? 

Black coffee is safe to drink when you’re in ketosis and aiming for measurable ketones.  Because it can accelerate metabolism and increase body fat breakdown, it may increase your ketone levels.

Does Milk in Coffee Break a Fast?  

Milk contains calories and can provide a substantial amount if you have a heavy pour.  Thus, coffee with milk — of any sort — will break your fast.  In Data Driven Fasting, you should treat anything with more than a hundred calories or so of cream, milk, butter, MCT, or sugar as a meal, check your blood sugar beforehand, and wait until you reach your trigger again before sipping. 

Many people quickly realise that they are sneaking more calories than they realised into their morning cuppa, and it keeps their blood glucose elevated for quite some time, meaning they have to wait several hours more before they can have their first real meal. 

Can I Have Cream in My Coffee While Intermittent Fasting?

Cream is known to have more fat than milk, which makes people believe it is ‘more keto’ than milk.  But don’t let its high-fat content fool you; this won’t stop it from breaking your fast! 

No matter the glycemic index, if an add-in has calories, this will force your body out of a fasted state so that it can burn off the energy you just consumed from food or a beverage before you need to start tapping into your body fat again. 

So yes, even if you see a smaller rise in blood sugars and insulin, calories — of any sort — will technically break your fast.

Can I Drink Coffee with Skim Milk While Intermittent Fasting?

Simply put: nope.  Similar to the answer above, skim milk contains calories that will force the body out of a fasted state.

Can I Drink Tea with Milk and Sugar During Intermittent Fasting?

A solo herbal, black, or green tea will not break your fast.  However, if you’re looking to stay in a fasted state, drinking it with milk, sugar, honey, or any add-in with calories will take you out of a fast.  So, what can you use to sweeten your day?

What About Artificial Sweeteners?

If you like a touch of sweetness with your bitter coffee, sugar can be challenging to part with.

Stevia is likely your best bet for a natural sweetener that won’t break your fast.  Interestingly, some studies have shown that stevia can even lower blood sugar

Allulose, a newer zero-calorie sweetener, may also be a viable option as it does not provide a substantial amount of calories nor trigger an insulin response.  However, it does stimulate the gut, which may rule it out if you’re fasting for a medicinal purpose.

A close third would be erythritol, although it comes in at ~0.2 calories/gram.  Thus, consuming small, modest amounts of it should not break your fast.  While monk fruit (luo han guo) is a great natural, zero-calorie alternative, some studies have shown that it might affect insulin.  Thus, it might not be the best if your goal is fat loss.

On the other hand, erythritol, mannitol, sorbitol, and other sugar alcohols (those ending in ?ol) contain about half the calories of regular sugar (~2 calories/gram).  Thus, they would break your fast.

To dive a little bit deeper, many argue that other zero-calorie sweeteners like aspartame, neotame, and advantame break a fast because they contain amino acids.  Other mainstream zero-calorie sweeteners like sucralose (Splenda) have been shown to alter the blood glucose response and gut function with multiple uses, which has been linked to insulin resistance.

If you’re curious about how the sweetener you prefer affects you, test!  It’s best to see how your body responds.  To do this, test your blood sugar before and each hour for two or three hours afterwards. 

What Else Can I Put in My Coffee That Won’t Break My Fast?

If you’re just not a fan of plain black coffee, there are a few zero-calorie ingredients you can add to make the best of your bitter morning bevvy.

Spicing is one of the best things you can do to diversify your morning coffee.  Ceylon cinnamon, nutmeg, anise, cardamom, turmeric, or the classic conglomerate of pumpkin spice are all warming, zero-calorie additions to make your coffee taste (and smell) to your liking.  If you’re adding in turmeric, be sure to add a dash or two of ground black pepper to make it anti-inflammatory.

Similar to spices, a sprinkle of cocoa should be okay for sprucing up your coffee without breaking your fast.  A sprig of mint or a sliver of ginger should also keep you in the fasting clear.  If you’re a fan of salt, feel free to add a dash of your favourite pink Himalayan, Celtic, or sea salt variety to your warm morning cup. 

What Will Break My Fast If I Add It to My Coffee or Tea?

Simply put, anything that contains a substantial amount of calories will break your fast.  This includes—but is not limited to—nut and seed milk, oat milk, coconut oil, cream, non-dairy creamers, honey, maple syrup, butter, ghee, gelatine, collagen, mushroom powders, and extracts (vanilla).

While some people may still produce ketones while consuming these high-fat add-ins, they are producing ketones from the dietary fat they’ve consumed that they’ve pushed their bodies to metabolise.  Thus, they are no longer in a fasted state.

Can You Drink Coffee While Water Fasting?

Many people debate on what constitutes breaking a water fast.  If you’re doing it for health reasons, many absolutists believe you must only consume water while fasting.  However, a lot of new-age water fasters believe black coffee is okay because it does not contain calories, nor does it provide sustenance.

Aside from this debate, it’s essential to remember that coffee is a diuretic, increasing the loss of water and minerals through the kidneys.  Because water fasting requires someone only to drink water, it can be hard to maintain hydration (i.e., water and electrolytes), which can contribute to some of the side effects of water fasting, like dizziness, fatigue, low energy, malaise, heart abnormalities, fainting, and even death.

So, if you’re water fasting #forhealth, it might not be a bad idea to save your coffee as a reward for when you eat again.

Can You Drink Coffee While Fasting for Bloodwork?

Much debate also exists around whether it’s okay to drink coffee if you’re fasting for bloodwork.  Consuming black coffee will not affect your results for most common labs you must fast for, like a cholesterol (lipid) panel, metabolic panel, or blood glucose.  That said, it’s always good to double-check with the blood lab or your doctor to make sure coffee won’t interfere with your labs.   

A Few Coffee Recipes for You to Try (or Avoid)

We’ve taken a few of the most common coffee combinations and given our review on whether they’re worth trying (or avoiding) if you’re interested in improving your metabolic health.  You can click on the links to see the full recipe and nutritional information. 

Bulletproof Coffee

Dave Asprey’s Bulletproof Coffee had the lowest nutrient density and satiety scores of all the coffee recipes we analysed.  Many people find this recipe keeps them feeling full throughout the morning.  However, this is likely because they filled their energy fuel tanks by consuming tons of calories from butter and MCT oil! 

Consuming too many calories from dietary fat might stabilise your blood sugars, but it still provides the most calories per gram.  Calories in still equal calories out, and where there is a positive energy balance, someone won’t be able to lose fat from their body or reduce their insulin across the day. 

Coffee with Cream and Stevia

This simple coffee with cream & stevia recipe is what I make for my wife Monica each morning.  The high-fat, low-insulin-stimulating cream and zero-calorie stevia keep her blood sugars super stable and give her a little energy (fuel) throughout the morning. 

This recipe is excellent for someone wanting some calories in the morning to hold off on breakfast.  However, if your goal is fat loss, you’ll want to minimise the cream.

Potassium Caramel Salted Coffee

If you recall, coffee is a diuretic, meaning it can increase how quickly we excrete electrolytes like potassium, sodium, calcium, and magnesium.  Our potassium caramel salted coffee provides adequate potassium and sodium to boost your mineral intake.  You can also add a little protein in the morning to jumpstart your metabolism. 

Ketogains Pre-Workout Coffee

It’s not always a great idea to work out on an empty stomach, especially if you’re looking to perform at your best in the gym!  However, you can swap your pre-workout for the Ketogains Pre-Workout Coffee to get some protein, energy, and a caffeine boost so you can give your all. 

Egg Yolk Fatty Coffee

This fatty egg yolk coffee recipe will give you a smooth start to your day.  The nutrient-dense egg yolks provide some critical vitamins and minerals, and the salt and caffeine will give you a nice energy boost.  While this recipe is not ideal for fat loss, it’s definitely a step up from Bulletproof Coffee!


We hope you’ve found this deep dive into everyone’s favourite drink — coffee — to be useful. 

The bottom line is that coffee is great for most people.  There’s no need to be concerned about the minor blips in blood sugar and insulin that may result – it won’t break your fast.  But if you’re adding heaps of extra calories from milk, sugar, cream, MCT oil, etc., then it will contribute to your long-term energy balance and keep your blood sugars elevated for longer. 

If your goal is weight loss, then learning to enjoy your coffee or espresso black might be smart, so you can enjoy a nice protein-focused breakfast earlier in the day to maximise satiety and stabilise your blood sugars for the rest of the day.