Can You Drink Coffee While Intermittent Fasting?
Can You Drink Coffee While Intermittent Fasting?
Here's the short answer: yes. Black coffee won't break your fast, and research suggests it might actually enhance some of fasting's benefits.
Here's the short answer: yes. Black coffee won't break your fast, and research suggests it might actually enhance some of fasting's benefits.
But like most things in nutrition, there's nuance. What you add to your coffee matters. The quality of your coffee matters more when you're fasting. And the science behind why coffee and fasting work well together is genuinely interesting.
Let's look at what the research actually shows, so you can make your morning cup work with your fasting goals rather than against them.

Does Black Coffee Break a Fast?
Black coffee contains approximately 3-5 calories per cup. That's well below the commonly cited "50-calorie threshold" that most experts agree won't meaningfully disrupt fasting benefits.
More importantly, a 2020 study published in Current Developments in Nutrition found that drinking black coffee after a 10-hour fast did not affect triglyceride or glucose levels. The researchers measured fasting glucose before and after coffee consumption and found differences "ranging from negligible to non-significant."
Translation: black coffee doesn't trigger the metabolic responses that would break a fast. Your body stays in its fasted state.
Coffee May Actually Enhance Fasting Benefits
Here's where it gets interesting. Coffee doesn't just avoid breaking your fast, it may actually support what fasting is supposed to do.
Autophagy Enhancement
Autophagy is the cellular "cleanup" process where your body removes damaged components and recycles them. It's one of the key benefits people seek from fasting.
A significant 2014 study published in Cell Cycle demonstrated that coffee is a potent, rapid inducer of autophagy in multiple tissues:
- Speed: Autophagy markers appeared within 1-4 hours after coffee consumption
- Organs affected: Liver, muscle, and heart all showed increased autophagic activity
- Duration: Effects were sustained throughout the experimental period
Here's the surprising part: both regular and decaffeinated coffee produced identical autophagy results. This means caffeine isn't responsible for the effect, it's the polyphenols, especially chlorogenic acid, that trigger autophagy.
The researchers propose that coffee's documented health benefits (reduced cancer, heart disease, and diabetes risk) may stem partly from its capacity to trigger this cellular cleanup.
Appetite Suppression
Fasting is easier when you're not hungry. Coffee helps here too.
Research from PubMed found that coffee, including decaffeinated, decreases hunger and increases PYY, a satiety hormone. Interestingly, caffeine alone (in water) had no effect on hunger hormones. The appetite-suppressing effects appear linked to coffee's polyphenols, not just the caffeine.
Metabolic Support
According to PMC research, consuming 5 cups of coffee daily was associated with 5.6% lower fasting insulin and 8.8% lower 2-hour glucose levels. Coffee appears to support the insulin sensitivity benefits that fasting aims to provide.
What About Cream, Sugar, and Butter?
This is where things get more complicated.
Sugar: Yes, It Breaks Your Fast
Any form of sugar, white sugar, brown sugar, honey, agave, flavored syrups, will break your fast. Sugar causes an insulin spike, which disrupts fat oxidation, blood sugar stability, and autophagy. Even small amounts matter.
If sweetness is non-negotiable, you're better off ending your fast and eating breakfast.
Cream and Milk: It Depends
A small amount of high-fat dairy (1 tablespoon or less) is generally considered acceptable for most intermittent fasting goals. Fats don't require significant insulin to metabolize.
The threshold: Keeping fat additions under 50 calories from non-sugary sources is widely accepted for weight management and metabolic health goals.
However: If you're fasting specifically to maximize autophagy, any calories may downregulate the process. Pure water fasting is recommended for maximum cellular cleanup.
Butter and MCT Oil (Bulletproof Coffee)
Bulletproof coffee (coffee + grass-fed butter + MCT oil) technically breaks a fast in the strictest sense, it contains significant calories.
However, MCT oil converts directly into ketones instead of glucose, keeping you in ketosis. The fat doesn't spike insulin the way carbohydrates would. For people following keto or focusing on fat adaptation, bulletproof coffee during a "fast" may support those goals.
Bottom line: If your goal is weight loss and you can stick to your eating window better with bulletproof coffee, it's probably fine. If your goal is maximum autophagy, stick to black coffee.

Why Coffee Quality Matters More When Fasting
When you're fasting, your stomach is empty. Coffee metabolizes faster, effects are amplified, and your system is more sensitive to what you put in it.
This is when coffee quality matters most.
Mycotoxins and Contaminants
Research shows mycotoxins (mold byproducts) are found in a significant percentage of commercial coffee, estimates range from one-third to over 90% depending on sourcing and processing. While your liver can handle normal exposure, fasting on an empty stomach means direct, unbuffered contact.
Pesticides
Coffee is a heavily sprayed crop. When you're fasting, you don't have food buffering absorption. Organic certification eliminates synthetic pesticide concerns.
Stomach Comfort
Coffee stimulates gastric acid production through both caffeine and polyphenols. On an empty stomach, this can cause discomfort for some people.
What helps:
- Dark roasts contain more N-methylpyridinium (NMP), which actually inhibits stomach acid production
- Wet-processed, properly stored coffee has fewer mycotoxins
- Organic certification eliminates pesticide concerns
- Air-roasted coffee removes chaff that can contribute to stomach irritation
Practical Fasting Coffee Guidelines
Based on the research, here's what works:
What Won't Break Your Fast
- Black coffee (any amount within reason)
- Decaf coffee (same autophagy benefits as regular)
- A splash of heavy cream (under 1 tbsp / 50 calories)
What Will Break Your Fast
- Any amount of sugar
- More than 50 calories of additives
- Milk (contains lactose, a sugar)
- Flavored creamers
Timing Considerations
Cleveland Clinic notes that cortisol naturally peaks around 6-8 AM. For some people, optimal first coffee is between 9:30-11:30 AM, after the natural cortisol spike subsides. But this is individual, if morning coffee works for you, the research doesn't say you're doing it wrong.
If Coffee Bothers Your Stomach
- Try dark roast (gentler on the stomach)
- Consider cold brew (lower titratable acidity)
- Start with small amounts
- Don't force it, some people genuinely don't tolerate coffee while fasting
Frequently Asked Questions
Does black coffee break intermittent fasting?
No. Black coffee contains only 3-5 calories, which is below the threshold that would disrupt fasting benefits. Research shows that black coffee doesn't affect fasting glucose or triglyceride levels. It may actually enhance fasting benefits by triggering autophagy.
Can I put cream in my coffee while fasting?
In small amounts (1 tablespoon or less), yes, for most fasting goals. Fat doesn't spike insulin significantly. However, if you're fasting specifically to maximize autophagy, any calories may reduce that benefit. Sugar and sweetened creamers will break your fast.
Does coffee help with intermittent fasting?
Yes, in multiple ways. Coffee suppresses appetite (making fasting easier), triggers autophagy (the cellular cleanup process), and may support insulin sensitivity. Research shows that both regular and decaf coffee induce autophagy within 1-4 hours of consumption.
Is decaf coffee okay during intermittent fasting?
Absolutely. Decaf provides the same autophagy benefits as regular coffee, the polyphenols (not caffeine) are responsible for this effect. Decaf also suppresses appetite similarly to regular coffee. If you're avoiding caffeine, decaf is a great fasting companion.
Does bulletproof coffee break a fast?
Technically yes, it contains significant calories from butter and MCT oil. However, because these are pure fats that don't spike insulin, bulletproof coffee keeps you in ketosis and may support fat adaptation goals. For strict autophagy benefits, stick to black coffee.

The Bottom Line
Coffee and intermittent fasting work well together. Black coffee won't break your fast, may enhance autophagy, helps suppress appetite, and supports the metabolic benefits you're fasting for. The research is genuinely supportive.
What matters is keeping it simple: black or with minimal fat (no sugar), quality beans that won't irritate an empty stomach, and listening to how your body responds.
At Ember, we roast organic, air-roasted coffee that's designed to be smooth and clean, exactly what you want when drinking on an empty stomach. If you're fasting and want coffee that works with your goals, quality matters more than ever.