Man starts his day right with a delicious cup of hot coffee.

Can (and Should) You Drink Coffee While Fasting? It Depends

If you’re a diehard Dunkin’ bro, the answer might be “no.”

Fast Facts

  • Yes, you can drink coffee while fasting, but stick to black coffee like drip coffee or espresso.
  • Regular coffee consumption is associated with numerous benefits, including appetite regulation, which might increase the success of your IF protocol.
  • If coffee is a trigger for GI problems or stress, avoid coffee on an empty stomach, and stop drinking coffee, if necessary.

You just started intermittent fasting (IF). Good choice. Thanks to recent research, we know IF has the potential to melt excess body fat (1), reduce inflammation (2), cut cravings (3), and protect against a variety of conditions and diseases (4).

But you also love coffee. (Don’t blame you.) Does drinking coffee break a fast? Rendering the precious benefits of your new IF protocol moot? We tapped registered dietitian Imashi Fernando, M.S., R.D. to find out.

About the Expert

Imashi Fernando, M.S., R.D., C.D.C.E.S. is a registered dietitian who works in a large hospital system as a clinical dietitian and provides one-on-one nutrition counseling through her virtual private practice, Brown Sugar Nutrition PLLC. She holds a master’s degree in Nutritional Sciences from the University of Washington.

Does Coffee Break a Fast?

It depends. One cup of coffee (eight ounces) contains about three calories and very small amounts of protein, fat, and trace minerals (5). For most people, one to two cups isn’t enough to initiate a significant metabolic change that would negatively affect a fast (6).  

That said, coffee with added ingredients like cream, creamer, or sugar contains more calories, and may cause a blood sugar response—which may break a fast. Here’s how Fernando breaks it down:

Does black coffee break a fast?

Nope. Go ahead and have that iced Americano. “Drinking moderately low to zero-calorie drinks—like coffee—during a fasting window is unlikely to significantly compromise your fast in any way,” says Fernando. Plus, some studies show that coffee may help lower hunger and suppress appetite (7), making it easier to stick to your fasting window, she adds. 

Does flavored coffee break a fast?

Most coffee shops inject their flavored drinks, like lattes and macchiatos, with syrups and sauces that contain sugar and corn syrup. “Just one pump can contain upwards of 10 grams of sugar (just under one-third of the recommended total daily sugar limit of 36 grams for men),” warns Fernando. “It’s best to limit these drinks altogether, but if choosing to indulge it should be done within your eating window.”

As for artificially flavored roast coffee like beans or pods that come in hazelnut, vanilla, or caramel flavors, Fernando notes that these are similar to drinking black coffee in that they have no extra calories or sugars. “It’s okay to consume artificially flavored coffee while fasting,” she says. “However, some studies suggest artificial flavoring [and sweeteners] may increase hunger (8) and the risk of type 2 diabetes (9) so it’s best to limit them in your diet when you can.”

Does coffee with cream or sugar break a fast?

Although coffee alone isn’t likely to negatively affect your fast, adding calorie-containing ingredients could. “Loading your cup with high-calorie additives like cream, milk, and sugar disrupts your fast and might limit the benefits of an IF protocol,” says Fernando. She recommends staying away from lattes and cappuccinos during your fasting window.

What can you put in coffee that won’t break a fast?

The general rule for what you can put in your coffee while fasting is anything that’s zero calories —in other words, leave it black. If you just can’t stomach black coffee, here are a few minimal-calorie, natural ingredients that won’t significantly affect your fast:

  • Ceylon cinnamon
  • Pure vanilla powder
  • Nutmeg
  • Cardamom
  • Cacao powder (in small amounts)
  • Natural, zero-calorie sweeteners like 100% monk fruit or stevia extracts

Unfortunately, buzzy supplements like collagen don’t qualify. Ditto for a splash of milk or almond milk—they contain too many calories. If you *must* drink your coffee with a splash of something, “try to limit whatever you add to no more than 30 calories to minimize any negative impact to the metabolic benefits of IF,” says Fernando.

Does Bulletproof coffee break a fast?

The one exception to the added ingredient rule: Bulletproof coffee. According to Fernando, if you’re combining keto and IF or your fasting goal is to stay in ketosis, it’s okay to indulge in the creamy blend of coffee, grass-fed butter or ghee, and MCT oil.

“Even though a cup of Bulletproof coffee packs around 230 calories, the calories come from quality fats and thus won’t shift you out of ketosis—the state your body enters when it’s burning fat—like carbs or protein,” she says. Each delicious cup will reward you with healthy fats to keep you full and fueled. Plus, the MCT oil might boost ketone production (10).

However, she explains if you’re doing a traditional fast and abstaining from all food, then yes, Bulletproof coffee will break your fast. “Ultimately, you need to decide if Bulletproof coffee is right for you based on your fasting goals,” she adds.

Pros of Drinking Coffee When Fasting

Many of the benefits of drinking coffee mirror the benefits of intermittent fasting. Here, a few.

Reduce inflammation

“Coffee is packed with antioxidants which work to neutralize oxidative stress-inducing and disease-promoting free radicals in the body, a process that lowers systemic inflammation (11),” says Fernando. Chronic inflammation is the root cause of many illnesses, from erectile dysfunction to heart disease. Research suggests that both intermittent fasting and coffee can help reduce inflammation (2, 12).

Improve metabolic health

Higher coffee intake is also associated with a decreased risk of metabolic syndrome (13, 14)—an inflammatory condition characterized by excess abdominal fat, high cholesterol, and elevated blood sugar levels. It’s also linked to a reduced risk of type 2 diabetes (15, 16), and heart disease (17).

Boost brain function

“Coffee contains caffeine, which stimulates the nervous system,” says Fernando, “It does this by promoting the release of neurotransmitters, or chemicals, which may also play a role in improved mood, cognitive and brain function.” Regular coffee consumption is associated with a reduced risk of mental decline, Alzheimer’s, and Parkinson’s disease (18).

In a fasted state, your body also produces energy from fat in the form of ketones (19), a process linked to improved brain function (20). “Some studies have shown that caffeine may promote ketone production, too (21),” says Fernando.

Cons of Drinking Coffee When Fasting

Drinking coffee on an empty stomach might not be right for everyone. A few reasons you might avoid coffee while fasting, below.

Might impair blood sugar control

Some studies suggest drinking coffee might actually increase blood glucose levels and prolong the duration of elevated blood sugars short term (22). Yet, others found coffee could have a positive effect on glucose metabolism long term (23).

“More studies are needed to fully understand the effect of coffee on blood sugar control,” advises Fernando. “Until then, practice moderation.” The US Food and Drug Administration (FDA) considers 400 milligrams of caffeine per day—the equivalent of 4 cups (8 ounces per cup) of coffee—safe for most healthy adults.

Heightens cortisol response

“There is some thought that drinking coffee first thing out of bed may interfere with your body’s ability to regulate cortisol balance,” says Fernando. Your cortisol levels are typically highest in the morning, due to the cortisol awakening response—which peaks 30 minutes after waking up (24).

“It is possible that combining coffee with this cortisol spike may promote longer periods of elevated cortisol, which could increase stress and cravings for snacks packed with sugar and fat,” she adds. “Therefore, it may be best to let your cortisol spike naturally when you wake up. Then add in the caffeine for an additional boost of energy about two to three hours later.”

Could cause digestive issues

We couldn’t leave out the obvious. Drinking coffee before breakfast may be more likely to trigger peristalsis—helping you go number two faster (25). However, coffee may increase stomach acid secretion, so those who have more sensitive stomachs or pre-existing gastrointestinal (GI) conditions like irritable bowel syndrome (IBS) may need to limit or avoid coffee intake (25, 26).

To settle unpleasant symptoms, Fernando suggests trial and error. “Some people tolerate decaf coffee better, others may find a splash of milk helps. Avoiding coffee on an empty stomach may also help, or try switching to tea which has less caffeine,” she says. “Experiment to find what works best for you.”

Unfortunately, if you do identify coffee as the trigger for your GI woes, Fernando advises the best course of treatment is to cut it out.

So, Should You Drink Coffee While Fasting?

If you don’t like drinking coffee, there’s no pressing reason to start. “While coffee contains antioxidants that can help reduce inflammation, so do many fruits, vegetables, whole grains, legumes, and healthy fats,” says Fernando. If you are intermittent fasting, Fernando points out you should still aim for a balanced diet during your eating window. If you do, it should be easy to obtain all of the nutrients you need.

However, if drinking coffee seems to make your fast a little easier, there’s no reason to quit. Just watch the added ingredients.

1.Kang, J. et al. (2022). Effects of an Intermittent Fasting 5:2 Plus Program on Body Weight in Chinese Adults with Overweight or Obesity: A Pilot Study.
2. Paoli, A. et al (2019). The Influence of Meal Frequency and Timing on health in Humans: The Role of Fasting. 
3. Zajac, I. et al (2021). Modified Fasting Compared to True Fasting Improves Blood Glucose Levels and Subjective Experiences of Hunger, Food Cravings and Mental Fatigue, But Not Cognitive Function: Results of an Acute Randomised Cross-Over Trial. 
4. Mattson, M. et al (2017). Impact of Intermittent Fasting on Health and Disease Process. 
5. United States Department of Agriculture, (2018). Beverages, Coffee, Brewed, Prepared with Tap Water. 
6. Dam, R. et al (2004). Effects of Coffee Consumption on Fasting Blood Glucose and Insulin Concentrations: Randomized Controlled Trials in healthy Volunteers.
7. Schubert, M. et al (2017). Caffeine, Coffee, and Appetite Control: A Review. 
8. Neumann, N. et al. (2022). Added Flavors: Potential Contributors to Body Weight Gain and Obesity?
9. Mathur, K. et al (2020). Effect of Artificial Sweeteners on Insulin Resistance Among Type 2 Diabetes Mellitus Patients. 
10. Vetrani, C. et al. (2023). Supplementation With Medium-Chain Fatty Acids Increase Body Weight During Very Low-Calorie Ketogenic Diet: A Retrospective Analysis In a Real-Life Study.
11. Yashin, A. et al (2013). Antioxidant and Antiradical Activity of Coffee. 
12. Paiva, C. et al (2019). Consumption of Coffee or Caffeine and Serum Concentration of Inflammatory Markers: A Systematic Review. 
13. Suliga, E. et al (2017). Coffee Consumption and the Occurrence and Intensity of Metabolic Syndrome: A Cross-Sectional Study. 
14. Grosso, G. et al (2015). Association of Daily Coffee and Tea Consumption and Metabolic Syndrome: Results From the Polish Arm of the HAPIEE Study. 
15. Carlstrom, M. et al (2018). Coffee Consumption and Reduced Risk of Developing Type 2 Diabetes: A Systematic Review With Meta-Analysis. 
16. Jiang, X. et al (2014). Coffee and Caffeine Intake and Incidence of Type 2 Diabetes Mellitus: A Meta-Analysis of Prospective Studies. 
17. Poole, R. et al (2017). Coffee Consumption and Health: Umbrella Review of Meta-analyses of Multiple Health Outcomes. 
18. Gardener, S. et al. (2021). Higher Coffee Consumption Is Associated With Slower Cognitive Decline and Less Cerebral Aβ-Amyloid Accumulation Over 126 Months: Data From the Australian Imaging, Biomarkers, and Lifestyle Study.
19. Anton, S. et al (2018). Flipping the Metabolic Switch: Understanding and Applying the Health Benefits of Fasting. 
20. Altayyar, M. et al (2022). The Implication of Physiological Ketosis on The Cognitive Brain: A Narrative Review. 
21. Vandenberghe, C. et al (2017). Caffeine Intake Increases Plasma Ketones: An Acute Metabolic Study in Humans. 
22. Dewar, L. et al (2017). The Effect of Acute Caffeine Intake on Insulin Sensitivity and Glycemic Control in People with Diabetes. 
23. Reis, C. et al (2018). Effects of Coffee Consumption on Glucose Metabolism: A Systematic Review of Clinical Trials.
24. Elder, G. et al (2014). The Cortisol Awakening Response—Applications and Implications for Sleep Medicine. 
25. Montoro, M. et al. (2022). Effects of Coffee on the Gastro-Intestinal Tract: A Narrative Review and Literature Update.
26. Koochakpoor, G. et al. (2021). Association of Coffee and Caffeine Intake With Irritable Bowel Syndrome in Adults.