Can You Drink Coffee While Fasting?

Yes, you can drink coffee while fasting if it’s black and free of added calories. Plain black coffee has 3–5 calories per 8 oz and does not affect fat burning, autophagy, or insulin sensitivity. However, for medical tests, bloodwork, or hormone checks, avoid coffee to prevent inaccurate results. The benefits of black coffee during intermittent fasting include appetite suppression, enhanced fat burning, improved brain function, and more.

The best coffee to drink while fasting are black americano, espresso, cold brew, iced, Nespresso, or decaf coffee from Arabica or Robusta beans. Avoid sugar, milk, cream, butter, honey, collagen, or sweeteners, as they can break a fast. The best coffee beans for fasting are freshly roasted Arabica beans from Ethiopia, Colombia, or Kenya. These high-altitude beans are larger in size, denser in structure, and packed with complex flavors without added calories.

Does Coffee Break a Fast?

No, black coffee does not break your fast. A standard cup of black coffee has almost no calories and does not contain fat, protein, or sugar. Because of this, it will not spike your insulin, start digestion, or change your metabolism during intermittent fasting or water fasting. A 2021 study published in Clinical Nutrition ESPEN by Christina M. Sciarrillo from Oklahoma State University found that black instant coffee doesn’t significantly affect fasting triglycerides or glucose levels. In the study, 15 healthy adults drank 240 ml of black coffee or water before a high-fat meal and showed no difference in fasting triglyceride levels.

While drinking black coffee during fasting supports autophagy, ketosis, and blood sugar control, adding calorie additives like whole milk, heavy cream, or sugar may break your fast. According to dietitian Roxana Ehsani, milk or cream—including oat, almond, or cow’s milk—breaks a fast due to its calorie content. However, some people on forums like Reddit share anecdotal stories about still losing weight while adding small amounts of cream or half-and-half to coffee during intermittent fasting. They report no noticeable effect on blood glucose or insulin, especially when using under 1 tablespoon of heavy cream per cup. This type of fasting is called “dirty fasting,” meaning small calorie intake may not disrupt fat loss goals, even if it technically breaks the fast.

Can You Drink Coffee while Fasting for Bloodwork?

No, you should avoid drinking coffee while fasting for bloodwork unless your doctor permits it. Bloodwork refers to laboratory tests that analyze components in your blood, such as glucose, cholesterol, and hormones, to get a baseline reading of your health. The main confusion about coffee and blood tests is believing fasting only means avoiding calories. This focus on calorie count is misleading. For instance, a 2010 study in Diabetes Care by endocrinologist Rupali Deopurkar, M.D., Ph.D., found that drinking black coffee before a blood test did not affect fasting triglyceride or glucose levels in a small trial. However, focusing only on these markers overlooks the main reason to avoid coffee before blood test, which is the caffeine itself.

The primary reason to avoid coffee before a fasting blood test is that caffeine stimulates the body. It raises blood pressure, increases cortisol, and releases fatty acids into the bloodstream. A 2020 study in the British Journal of Nutrition found that drinking caffeine before a blood test may affect markers beyond glucose. The researchers observed interactions between caffeine and genes linked to caffeine metabolism. These interactions affected lipid levels, CRP, and hormone-related biomarkers. The effects were stronger in older adults and people with more body fat. For accurate bloodwork, especially for hormones, cholesterol, or metabolic markers, drink only water unless your doctor advises otherwise.

What are the Benefits of Black Coffee while Fasting?

The benefits of black coffee while fasting include appetite suppression, enhanced fat burning, improved brain function, reduced inflammation, and increased autophagy.

• Suppresses Appetite: Drinking black coffee while doing intermittent fasting, time-restricted eating, or alternate-day fasting helps suppress appetite by reducing hunger and food cravings. This makes it easier to stick to a fasting schedule. A 2019 study in Nutrients found caffeine in black coffee reduces hunger by stimulating the central nervous system. A 2022 study in Metabolism confirmed caffeine decreases appetite perception during fasting, with participants reporting lower hunger levels after consuming black coffee.
• Enhances Fat Burning: Plain black coffee enhances fat burning during intermittent fasting, water fasting, or the Daniel Fast. It promotes the use of stored fat for energy, which supports weight loss. A 2017 study in Sleep Medicine Reviews states that caffeine increases metabolic rate and fat oxidation through adrenaline release. A 2021 study in International Journal of Molecular Sciences indicates that caffeine reduces fat storage and promotes fat burning during fasting, though human evidence is limited.
• Improves Brain Function: Drinking black coffee while fasting improves brain function by increasing focus, alertness, and cognitive performance. A 2014 study in Cell Cycle found caffeine enhances alertness and counters fasting-related fatigue. A 2021 study in Frontiers in Aging Neuroscience showed moderate coffee intake is linked to slower cognitive decline, amplified by fasting’s ketone production. A 1993 study in Neuropsychobiology confirmed caffeine improves concentration in fasted states.
• Reduces Inflammation: Drinking black coffee while fasting reduces inflammation by lowering pro-inflammatory markers and helping decrease chronic disease risk. A 2023 review in Critical Reviews in Food Science and Nutrition found coffee’s polyphenols reduce inflammatory markers, complementing fasting’s effects. A 2019 study in Clinical Nutrition showed coffee consumption is associated with lower C-reactive protein levels in fasting individuals. Fasting and coffee both reduce metabolic syndrome risk, per a 2021 Advances in Nutrition study.
• Increases Autophagy: Drinking black coffee while fasting is valuable for increasing autophagy by supporting the breakdown and recycling of damaged cells, which promotes repair, longevity, and protection from age-related diseases. A 2014 study in Cell Cycle found coffee induces autophagy in vivo, with both regular and decaf coffee triggering this process due to polyphenols. A 2010 study in Autophagy confirmed caffeine enhances autophagy in fasting states, accelerating cellular cleanup compared to fasting alone.

What Coffee Can You Drink While Fasting?

You can drink black coffee, cold brew, iced coffee, Nespresso, or decaf made from Arabica or Robusta beans while fasting, as long as it contains no sugar, milk, or sweeteners. These options are nearly calorie-free and do not interfere with fat burning, blood glucose, or autophagy. Mushroom coffee and flavored coffee are also safe if flavorings contain no calories or carbs. Limit intake to 3–4 cups per day. The following list shows what coffee to drink during intermittent fasting.

1. Black Coffee
2. Instant Coffee
3. Decaf Coffee
4. Mushroom Coffee
5. Flavored Coffee

1. Black Coffee

You can drink up to 3–4 cups of black coffee per day during intermittent fasting. Plain black coffee such as espresso, drip, pour over, or Moka pot without milk, cream or sugar contains almost no calories (about 3–5 per cup) and does not disrupt intermittent fasting benefits such as fat burning, insulin sensitivity, or autophagy. A 2020 research published in Current Developments in Nutrition by Bryant Keirns from Oklahoma State University found that drinking black coffee after a 10-hour fast did not affect triglyceride or glucose levels. Ten adults completed two sessions—one with water, one with 8 oz black coffee—followed by a high-fat test shake. Results showed no difference in metabolic response between the two groups.

2. Instant Coffee

You can drink up to 3–4 cups of plain instant coffee per day while fasting if it contains no additives like sugar, milk, or high calorie flavoring. Instant coffee is brewed coffee that’s been freeze- or spray-dried into granules for quick preparation with hot water. When consumed plain, it contains few calories and does not break a fast. A 2020 study in the American Journal of Clinical Nutrition by Derrick Johnston Alperet from National University of Singapore (NUS) found that drinking four cups of plain instant coffee daily for 24 weeks had no effect on insulin sensitivity or fasting glucose levels in overweight adults.

3. Decaf Coffee

You can drink decaf coffee while fasting if it’s plain and free of additives. Decaf coffee is made by removing most caffeine using water, solvents, or carbon dioxide. Like black coffee, it has minimal calories and won’t break a fast if consumed without cream, butter, or sugar. A 2012 study published in the American Journal of Clinical Nutrition by Keizo Ohnaka from Kyushu University found that drinking five cups of decaffeinated coffee daily over 16 weeks did not significantly affect fasting glucose or insulin sensitivity in overweight adults. There is no strict limit for decaf coffee while fasting if it’s plain and calorie-free. Most people can safely drink 1–3 cups (8–24 oz) per day during a fast.

4. Mushroom Coffee

Mushroom coffee is suitable for fasting if it contains no added sugars, creamers, or significant calories. Mushroom coffee is a beverage made by blending ground coffee with powdered medicinal mushrooms like Cordyceps, Chaga, or Lion’s Mane. A 2023 study in Molecules by Paulina Łysakowska states that 100 grams of dried Cordyceps or Chaga contains 250–300 calories, or 2.5–3 calories per gram. A 1–2 gram serving of mushroom powder adds 2–6 calories per cup, which is below the 50-calorie threshold for intermittent fasting. One to three cups of plain, unsweetened mushroom coffee are safe during fasting, provided no caloric additives are included.

5. Flavored Coffee

You can drink flavored coffee while fasting if it contains no added sugars, syrups, or creamers. Flavored coffee refers to beans infused with natural or artificial flavor compounds such as vanilla, cocoa, or hazelnut. These beans typically add taste without calories. A 2019 study published in Nutrients by Janina Rynarzewski found that 2.5 g of flavanol-rich cocoa did not impact glucose, insulin, or triglyceride levels in people with type 2 diabetes. Flavored coffee with small amounts of natural cocoa added after roasting is unlikely to break a fast. You can drink it like black coffee—1 to 3 cups or more per day—without breaking your fast.

What Coffee Should You Avoid While Fasting?

You should avoid coffee with added sugar, milk, cream, butter, honey, collagen, flavored syrups, or sweetened creamers while fasting. These additives contain calories that can break your fast and disrupt fat burning, autophagy, or insulin sensitivity. Stick to plain black coffee, cold brew, or unsweetened decaf to stay in a fasted state.

• Coffee with Sugar: Any sugar or flavored syrup breaks a fast by causing an insulin spike that stops fat burning. Even small amounts of white sugar, brown sugar, honey, agave, or syrups contain enough calories and carbs to disrupt fat oxidation and blood sugar balance.
• Coffee with Milk: Avoid adding milk, half-and-half, or cream to coffee during fasting, as all contain calories and lactose that trigger insulin and break a fast. Heavy cream has less impact than milk but still breaks a strict fast. For autophagy or metabolic health, drink black coffee only.
• Coffee with Sweeteners: Even "natural" zero-calorie sweeteners like stevia, allulose, and monk fruit are debated in fasting communities. While they don’t contain calories or carbs, they may stimulate cravings and trick the body into expecting food, potentially dampening fasting effects. If strict fasting is your goal, it’s best to avoid all sweeteners and keep coffee completely black.
• Bulletproof Coffee: Bulletproof coffee breaks a true fast because butter and MCT oil contain calories, even though they don’t spike insulin. Fat-only coffee, such as "keto coffee" may help in keto or fat fasting by supporting ketosis and reducing hunger, but it limits autophagy and deep fasting benefits. For full fasting effects, choose plain black coffee instead.
• Collagen Coffee: Collagen coffee breaks a fast because collagen provides 20–35 calories and triggers digestion and insulin release. This disrupts autophagy and gut rest. For fat loss or metabolic flexibility, moderate collagen may be acceptable. It has little effect on ketones and fits fasting methods that allow under 50 calories.
• Protein Coffee: Protein coffee breaks a fast because protein powder contains calories and triggers insulin and digestion. This stops fasting benefits like autophagy and fat burning. To stay fasted, avoid protein during fasting and only consume it during the eating window of plans like 16/8.

How to Choose the Best Coffee for Fasting?

To choose the best coffee for fasting, follow the 5 steps below.

1. Choose plain black coffee: Select black coffee without milk, cream, sugar, or flavorings. It contains only about 3 calories per 8 oz and won’t break your fast. High-quality Arabica single origin coffee contains no additives but offers natural flavors like citrus in Ethiopian Sidama and chocolate or nuts in Colombian Tolima.
2. Avoid insulin-spiking additives: Skip anything with calories or sweeteners that can raise insulin levels and disrupt autophagy such as honey, condensed milk, maple syrup, or flavored milk.
3. Select coffee based on acidity and flavor: Choose light roast specialty coffee for more subtle flavors or dark roast low-acid options if you have a sensitive stomach.
4. Match caffeine level to your tolerance: Use caffeinated coffee to support focus and fat burning, or Swiss Water Process decaf if you're caffeine-sensitive but still want antioxidants.
5. Use fasting-friendly brewing methods: Drip, espresso, Americano, instant, and French press are all suitable as long as you don’t add extras.
6. Limit intake and time it wisely: Stick to 2–3 cups during your fast and avoid drinking coffee late in the day to protect sleep and fasting effects.

Where to Buy the Best Coffee for Fasting?

The best place to buy the best coffee for fasting is Colipse Coffee. We provide single-origin and blended coffees with natural flavor notes and no added sugars. The selection includes beans from high- and low-altitude regions, offering diverse taste profiles and high quality. Blends are tailored for brewing methods such as espresso and French press. Whole bean or pre-ground options in medium, coarse, or fine grinds are available to suit various brewing styles. Flavored coffees use natural extracts and oils, free of synthetic additives or sweeteners, to maintain fasting compliance.

What’s the Best Time to Drink Coffee while Fasting?

The best time to drink coffee while fasting is during the morning or early fasting window, typically within the first 2–4 hours after waking. This supports alertness, helps suppress appetite, and minimizes sleep disruption. Avoid drinking coffee late in the fast, especially in the afternoon or evening, to protect circadian rhythm and sleep quality.

Is Black Coffee Good for Weight Loss?

Yes, black coffee supports weight loss, according to the European Journal of Nutrition. A 2015 study found that drinking 3 or more cups daily was linked to lower BMI, waist size, and triglycerides, and higher HDL cholesterol. Coffee without sugar also lowered the risk of metabolic syndrome by 25%, based on data from the HAPIEE study in Poland.

Does Drinking Black Coffee Count as Water Intake?

Yes, drinking black coffee in moderation (2–3 cups per day) contributes to daily hydration, especially for regular coffee drinkers. A 2014 University of Birmingham study found that four mugs of instant black coffee provided hydration equal to the same amount of water. However, while black coffee can be hydrating for regular coffee drinkers, it might not be a perfect substitute for water, especially for those who don't drink it habitually.

A 1997 clinical trial at Justus Liebig University showed that non-habitual coffee drinkers experienced a significant increase in urine output (753 ml) along with the loss of electrolytes like sodium and potassium, leading to a negative fluid balance and temporary dehydration after consuming six 8-ounce cups of black coffee in one day.