If you decide to try intermittent fasting, you've probably mentally prepared yourself to get through the morning without your favorite oatmeal or breakfast smoothie. It's worth a little adjustment for all of the benefits, right?
But one thing you may have forgotten to consider is your morning cup of coffee.
Will your much-needed pick-me-up break your fast? And if it will, is that a deal-breaker for your plan to attempt intermittent fasting?
In this article, we'll discuss how coffee can interfere with intermittent fasting, and how it could actually benefit your fast.
We'll also talk about the best way to fast without giving up your coffee habit, and the best things to eat when you're ready to break your fast.
Intermittent Fasting Overview
Intermittent fasting isn't just a diet—it's an eating pattern that cycles between periods of fasting and eating. Several approaches have gained popularity, each with its own structure:
Time-Restricted Eating (16/8 Method): Perhaps the most accessible approach, this involves fasting for 16 hours and restricting your eating to an 8-hour window each day. Many people find this method sustainable because part of the fasting period occurs during sleep.
5:2 Method: This approach involves eating normally five days a week while restricting calories to about 500-600 on two non-consecutive days.
Alternate-Day Fasting: As the name suggests, this method alternates between fasting days and regular eating days.
Metabolic-Rest Fasts: Shorter fasting periods (12-14 hours) designed primarily for metabolic health rather than weight loss.
During your eating window, the quality of your diet remains crucial. Intermittent fasting works best when combined with nutritious, whole foods rather than processed options.
Loading up on vegetables, lean proteins, healthy fats, and complex carbohydrates during eating periods ensures you're getting essential nutrients while managing your eating schedule.
The relationship between coffee and intermittent fasting extends beyond simply allowing black coffee during fasting periods.
For many practitioners, coffee becomes an important tool that helps manage hunger, provides mental clarity, and potentially enhances some of the metabolic benefits associated with fasting.
The key is understanding how to incorporate coffee strategically without undermining your fasting goals.
Does Black Coffee Break Intermittent Fasting?
Good news - black coffee won't interfere with intermittent fasting. The key factor for what will or won't break your fast is calories. If what you're consuming is calorie-free (or around 5 calories or less per serving), your fast will continue.
Keeping your body in a fasting state all comes down to blood sugar. When you're in the middle of a fast, your blood sugar is stable. However, consuming calories causes your blood sugar to increase and ends your fast.
According to a small randomized-controlled trial on black coffee and fasting metabolic markers, coffee intake did not affect blood sugar levels after consumption.
Some other calorie-free beverages that are safe for fasting include zero-calorie club soda, black tea, green tea, and water.
Impact of Black Coffee on Fasting
To understand why black coffee doesn't break a fast, we need to look at both its caloric content and metabolic impact.
A standard 8-ounce cup of black coffee contains approximately 2-5 calories—an amount so minimal that it doesn't trigger a significant insulin response or affect your blood glucose levels. Without this metabolic shift, your body remains in a fasted state.
The caffeine in coffee may actually complement the fasting process.
Research suggests caffeine can increase fat oxidation, essentially enhancing your body's ability to burn fat during the fasting period. This may contribute to the fat-burning benefits many seek from intermittent fasting.
Additionally, coffee contains compounds that may help suppress appetite, making your fasting windows more manageable.
According to a 2017 review on caffeine, coffee, and appetite control, consuming caffeine, such as a cup of black coffee, 30 minutes to 4 hours before a meal, may suppress energy intake.
Timing your coffee consumption during fasting can make a difference in its effectiveness. Many experts recommend drinking coffee earlier in your fasting window, as caffeine has a half-life of approximately 5-6 hours.
This timing helps avoid potential sleep disruptions while maximizing the appetite-suppressing effects when hunger might be most challenging to manage.
Decaffeinated coffee provides similar benefits for those sensitive to caffeine, though some of the metabolic benefits may be slightly reduced without caffeine's stimulating effects.
Like regular black coffee, decaf contains minimal calories and won't disrupt your fast when consumed without additives.
Herbal teas can serve as alternatives for those who want variety in their fasting beverages. Like black coffee, most herbal teas are calorie-free and won't impact your metabolic-health gains from fasting when consumed without sweeteners or milk.
Does Half and Half in a Coffee Break a Fast?
It's easy to assume that since half and half isn't flavored, adding a little to your coffee won't do any harm. However, even a small amount can derail your fast.
Once you start pouring your favorite add-ins into your coffee, you add calories, fat, and sugar.
Even just a small amount of milk will affect your blood sugar enough to break your fast. Other coffee mix-ins to avoid in order to keep your fast include:
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Sugar
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Cream
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Honey
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Protein Powder
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Butter
Additives in Coffee and Fasting
Understanding how various additives affect your fast can help you make informed decisions about your coffee during fasting periods.
Milk and Cream Alternatives
Even small amounts of traditional dairy can break a fast, but what about alternatives?
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Almond milk: Unsweetened almond milk contains about 30-40 calories per cup, but even a splash (1 tablespoon, or about 4 calories) may technically break a fast, though the impact is minimal.
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Coconut milk: At 45 calories per tablespoon, coconut milk will definitely interrupt fasting.
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Oat milk: With approximately 120 calories per cup, even a small amount will break your fast.
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Heavy cream: Despite being mostly fat (which has less impact on insulin than carbs), its 50 calories per tablespoon will end your fast.
The general rule: if your coffee additive contains calories, it will break your fast to some degree. The stricter your fasting goals, the more you should stick to black coffee.
Artificial Sweeteners and Natural Alternatives
Research on artificial sweeteners during fasting shows mixed results:
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Stevia: This natural, zero-calorie sweetener appears to have minimal impact on insulin levels, making it one of the safer options during fasting.
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Monk fruit: Similar to stevia, monk fruit sweetener doesn't contain calories and shows little effect on blood sugar or insulin.
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Artificial sweeteners like aspartame, sucralose, and saccharin: While technically calorie-free, some studies suggest these may trigger insulin responses through taste receptors. The effect varies greatly between individuals.
If you're fasting specifically for metabolic health or insulin sensitivity, even zero-calorie sweeteners might be best avoided. For weight management goals, they're less likely to interfere significantly.
Other Flavor Enhancers
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Cinnamon, nutmeg, and other spices: These add flavor without calories and may even have beneficial effects on blood sugar.
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Flavored syrups: Most contain sugar and calories, making them incompatible with fasting.
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Bulletproof coffee (coffee with added butter and/or coconut oil): This trendy preparation definitely breaks a fast due to its high calorie and fat content. However, some keto practitioners use it strategically, arguing it maintains some benefits of fasting by avoiding carbohydrates and protein.
Does Coffee Affect the Benefits of Intermittent Fasting?
Plain black coffee is more than just okay for your fast. It can actually add to the benefits of intermittent fasting.
First and foremost, coffee helps you feel like you're consuming something. For many people, this is really important to make fasting a sustainable habit. Even if it's not providing calories, having something to sip is helpful to stay satisfied during a fast.
Here are some other ways coffee supports the benefits of intermittent fasting:
Promotes blood sugar control
Intermittent fasting is best known for blood sugar control and reducing insulin resistance. Drinking coffee has also been linked to better blood sugar control, which can boost potential benefits like preventing type 2 diabetes.
According to a 2018 systematic review and meta-analysis, there is an inverse association between coffee consumption and the risk of type 2 diabetes.
Fights inflammation
Fasting has been shown to decrease markers of chronic inflammation and therefore lower the risk for disease. Coffee has actually been shown to have the same effect, with the added benefit of antioxidants (try to go for high-quality organic coffee if you can).
Supports brain function
Although more research is needed, some studies show a link between fasting and improved brain health. Some of the benefits come from decreased inflammation. People who fast often report that they experience more mental clarity.
It's no secret that coffee makes us feel more alert and sharp, which only adds to the benefits you could experience from fasting.
Boosts metabolism and reduces appetite
Intermittent fasting helps some people consume fewer calories and can even boost metabolism. One study even found that fasting promotes fat loss while preserving muscle more effectively than simple calorie restriction.
Coffee is also known to temporarily boost metabolism and suppress appetite, which may add to your calorie deficit and boost weight loss.
Benefits of Coffee During Fasting
Beyond the benefits already mentioned, coffee offers several advantages specifically relevant to those practicing intermittent fasting:
Enhanced Fat Burning
Coffee doesn't just passively accompany your fast—it actively contributes to fat metabolism.
The caffeine in coffee stimulates your sympathetic nervous system and increases the release of catecholamines like adrenaline, which signal fat cells to break down. This process, called lipolysis, releases fatty acids that can be used for energy during your fast.
Studies have shown that caffeine can increase metabolic rate by 3-11%, with larger effects observed in leaner individuals. This metabolic boost primarily comes from increased fat burning, which aligns perfectly with the goals of most intermittent fasting protocols.
When combined with the natural metabolic switch that occurs during fasting (where your body shifts from using glucose to using ketones for fuel), coffee may help accelerate the transition into a fat-burning state.
Appetite Regulation
One of the biggest challenges of fasting is managing hunger, and coffee offers significant benefits in this area. Caffeine appears to temporarily suppress the production of ghrelin, your body's primary hunger hormone.
“As a Registered Dietitian, I see clients use this method during unintentional fasts, such as forgetting to eat breakfast, because it works that well.”
Additionally, coffee stimulates the production of peptide YY (PYY), a hormone that signals fullness.
These hormonal effects typically last 3-4 hours after consumption, which can help you navigate the most challenging parts of your fasting window.
Some research suggests that the chlorogenic acids in coffee may also help slow gastric emptying and promote feelings of fullness, independent of caffeine's effects.
For many people, strategically timing coffee consumption during fasting (such as having a cup when hunger typically strikes) can make the difference between successfully completing a fast and breaking it prematurely.
Cognitive Function Enhancement
The mental clarity often reported during fasting may be amplified by coffee consumption. While fasting, your body increases production of brain-derived neurotrophic factor (BDNF), a protein that supports brain health.
Caffeine complements this by blocking adenosine receptors, which increases neuronal firing and the release of dopamine and norepinephrine.
This combination can result in:
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Improved attention and vigilance
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Enhanced working memory
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Increased capacity for problem-solving
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Better mood and reduced perception of effort
These cognitive benefits can be particularly valuable during fasting periods when some people initially experience brain fog or difficulty concentrating as their bodies adapt to using ketones instead of glucose for energy.
Potential Autophagy Enhancement
Autophagy—the cellular "cleaning" process that removes damaged components—is one of the most sought-after benefits of fasting.
Preliminary research suggests that certain compounds in coffee, particularly polyphenols, might actually enhance autophagy.
While more human studies are needed, this potential benefit makes coffee an intriguing complement to fasting protocols specifically targeting cellular health and longevity.
What Can I Put In My Coffee That Won't Break a Fast?
Now that we know that our favorite creamer is off the table while we're in the middle of a fast, is there any way to flavor our coffee that won't interfere?
For most people, the best way to do this is with an artificial sweetener. Choose something like Stevia or monk fruit that provides sweetness without calories or sugar. Many prefer these over other artificial sweeteners like aspartame because they're more natural.
If sweeteners aren't your thing, a sprinkle of cinnamon only gives a hint of flavor, but could still do the trick.
Guidelines for Coffee Consumption While Fasting
To maximize the benefits of coffee during your fasting periods while minimizing potential drawbacks, consider these practical guidelines:
Timing Considerations
The when matters almost as much as the what when it comes to coffee during fasting:
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Early morning consumption: Most experts recommend having coffee within the first 8 hours of your fasting window. This timing capitalizes on coffee's appetite-suppressing effects when hunger might be strongest while giving caffeine enough time to clear your system before bedtime.
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16/8 time-restricted eating: If following this popular method (16 hours fasting, 8 hours eating), consider having your first cup shortly after waking and a second cup mid-morning if needed.
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Avoid afternoon consumption: Even if you're still fasting, limiting coffee after 2 PM helps prevent potential sleep disruptions, which can undermine the hormonal benefits of fasting.
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Pre-workout timing: If exercising while fasted, having black coffee 30-60 minutes before your workout may help mobilize fat stores and improve performance without breaking your fast.
Suitable Coffee Types
Not all coffee is created equal for fasting purposes:
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Choose higher-quality coffee: Organic, single-origin coffees typically contain more beneficial compounds and fewer pesticides. These coffees often have a more complex flavor profile that makes black coffee more enjoyable.
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Cold brew considerations: Cold brew coffee tends to be less acidic, making it gentler on an empty stomach for those prone to gastrointestinal discomfort during fasting.
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Avoid artificially flavored roast coffee: While technically "black" coffee, some flavored coffees may contain small amounts of added ingredients that could potentially impact your fast.
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Espresso vs. drip coffee: Both are suitable during fasting, but espresso delivers caffeine more quickly while drip coffee provides a longer-lasting effect. Choose based on your preference and timing needs.
Hydration Balance
Coffee has a mild diuretic effect that should be managed during fasting:
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Follow the 1:1 rule: For each cup of coffee, drink at least one equal-sized cup of water to maintain hydration during fasting.
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Consider electrolytes: During longer fasts (24+ hours), adding electrolytes to your water can help maintain proper hydration without breaking your fast.
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Monitor your body's signals: Excessive thirst, headaches, or dizziness during fasting may indicate dehydration that's being exacerbated by coffee consumption.
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Total caffeine intake: The FDA suggests limiting caffeine to about 400mg daily (roughly 4 cups of coffee). During fasting, your body may be more sensitive to caffeine, so consider a lower limit.
For those combining keto and IF (intermittent fasting), coffee can help facilitate the transition into ketosis while fasting.
Zero-calorie drinks like water should still make up the majority of your fluid intake during fasting periods, with coffee serving as a strategic tool rather than your primary hydration source.
Potential Drawbacks of Coffee During Fasting
While coffee can enhance your fasting experience, it's important to be aware of potential challenges it may present:
Digestive Considerations
Drinking coffee on an empty stomach affects people differently:
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Increased stomach acid: Coffee stimulates gastric acid production, which may cause digestive discomfort, particularly for those with gastrointestinal conditions like acid reflux, gastritis, or IBS.
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Individual tolerance varies: Some people can drink multiple cups of black coffee while fasting with no issues, while others experience nausea or stomach pain after just a small amount.
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Adaptation period: Your digestive system may gradually adjust to coffee during fasting. Starting with small amounts and slowly increasing can help minimize discomfort.
To mitigate these issues, consider stomach-friendly coffee options like cold brew or low-acid coffee beans, which tend to be gentler on an empty stomach.
Sleep Impact
The relationship between fasting, coffee, and sleep requires careful management:
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Extended caffeine sensitivity: During fasting, some people experience heightened sensitivity to caffeine, with effects lasting longer than usual.
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Cortisol response: Coffee increases cortisol production, which can be beneficial in the morning but potentially disruptive to your hormonal balance if consumed later in the day.
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Sleep quality affects fasting benefits: Poor sleep from late caffeine consumption can undermine the hormonal benefits of fasting by affecting insulin sensitivity and hunger hormones.
Limiting coffee to the first half of your day can help prevent these sleep disruptions while still providing the beneficial appetite-suppressing effects when they're most needed.
Metabolic Considerations
Some research raises questions about certain aspects of coffee consumption during fasting:
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Autophagy effects: While coffee may support autophagy in some ways, excessive caffeine might potentially affect the mammalian target of rapamycin (mTOR) pathway, which plays a role in autophagy regulation. Research in this area is still emerging.
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Individual variability in blood sugar response: Although black coffee doesn't contain calories, some individuals may experience a minor insulin response to coffee. This varies greatly between people and typically isn't significant enough to negate fasting benefits.
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Adaptation changes: Regular coffee consumers may develop tolerance to some of coffee's metabolic effects over time, potentially reducing both benefits and drawbacks.
Most experts agree that for the average person, the potential benefits of moderate coffee consumption during fasting outweigh these considerations, but individual responses should guide your approach.
What Is the Best Way to Properly Break a Fast?
Ideally, you won't break a fast with a huge meal. You'll feel better if you ease back into eating so your digestive system has a chance to wake up.
A meal that's high in fat, fiber, sugar, or sodium will probably leave you feeling bloated and ready for a nap. Instead, try eating something balanced and light like:
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Smoothie - Easy to digest and you can easily boost the nutrition with a gut-friendly supplement like Naked Greens and Naked Collagen.
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Vegetables - Cooked veggies are easier to digest. Something starchy like sweet potato is a great option.
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Dried fruit - Gives you a lot of energy in a small portion so you can ease back into eating.
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Eggs - Provide the perfect ratio of healthy fat and protein in a small serving.
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Yogurt - Gives you the added benefit of probiotics to promote gut health.
The key to breaking a fast is to give your body time to adjust. If you're new to fasting, you might have to experiment and see what works for you.
Key Takeaways
You can definitely drink coffee while intermittent fasting. However, you'll need to leave out your cream and sugar and opt for black coffee or artificial sweeteners instead.
Drinking coffee gives you something to sip on, which makes a fast a little more enjoyable for some people. Coffee also brings some additional health benefits to your fast, like a small metabolism boost, appetite suppression, reduced inflammation, and mental clarity.
When you're ready to break your fast, the most important thing is to go easy on your digestive system. Plan to eat something that packs a lot of nutrition in small, easy-to-digest does like a smoothie.