What kind of coffee can I have while fasting?

October 14, 2025 •

2 min read

Over 20 million people practice some form of intermittent fasting, making it one of the most popular dietary patterns today. A common question among those following this regimen is: What kind of coffee can I have while fasting? The simple answer for most is plain, black coffee, but the details matter for a successful fast.

Quick Summary

An overview of fasting-safe coffee options, explaining why black coffee is permissible while high-calorie additives like milk and sugar should be avoided. The article also discusses decaf and flavor additions that won't disrupt the fasted state.

Key Points

Plain Black Coffee: An 8-ounce cup of plain black coffee contains only 3-5 calories and will not break a fast for most people.
Avoid Calorie-Based Additives: Adding milk, cream, sugar, or high-calorie flavor syrups will break your fast by spiking insulin levels.
Decaf is Fasting-Friendly: Decaffeinated coffee is a great alternative for those sensitive to caffeine, as it still contains beneficial antioxidants without the stimulant effects.
Use Spices for Flavor: To enhance the taste of black coffee without breaking your fast, try adding zero-calorie spices like cinnamon or nutmeg.
Practice Moderation and Hydration: Limit coffee intake to 2-4 cups per day and ensure you drink plenty of water, as coffee can have a diuretic effect.

The Golden Rule: Plain Black Coffee

For most fasting protocols, plain black coffee is the go-to beverage. An 8-ounce cup typically contains just 3-5 calories and negligible macronutrients, which is usually not enough to trigger a significant insulin response and break your fast. This allows key metabolic processes like fat burning and autophagy to continue.

Several types of pure, black coffee are suitable during a fasting window, including drip or pour-over, espresso, cold brew, and plain instant coffee. Decaf coffee is also an option.

Fasting-Friendly Coffee and Its Benefits

Black coffee can also be beneficial while fasting due to its caffeine content. Caffeine can help suppress appetite, boost metabolism temporarily, and improve mental clarity and energy.

Common Additives That Break Your Fast

Adding calories, particularly from carbohydrates or protein, will trigger an insulin response and break your fast. This includes sugars, syrups, milk, cream (dairy and plant-based), and bulletproof coffee. Artificial sweeteners are debated and may be best avoided for a strict fast.

Creative Ways to Flavor Fasting-Safe Coffee

To enhance plain black coffee without breaking your fast, consider zero-calorie additions like spices (cinnamon, nutmeg, unsweetened cocoa powder) or focusing on high-quality beans.

Potential Downsides and Best Practices

While coffee can be helpful, be aware of potential drawbacks, such as stomach irritation, sleep disruption, jitters, or anxiety. It also has a diuretic effect, requiring increased water intake. Moderate intake, typically 2-4 cups per day, is recommended.

Comparison Table: Fasting-Friendly vs. Fast-Breaking Coffee


Coffee Type	Status	Key Reason
Black Coffee (Hot or Cold Brew)	Fasting-Friendly	Contains minimal calories; does not trigger an insulin response.
Decaf Black Coffee	Fasting-Friendly	Very low calorie and no caffeine; still offers antioxidants.
Black Coffee with Cinnamon/Nutmeg	Fasting-Friendly	Spices add flavor without significant calories or sugars.
Black Coffee with Sugar/Honey	Breaks Fast	Sugar and carbs cause an insulin spike and end the fasted state.
Black Coffee with Milk/Cream/Oat Milk	Breaks Fast	Contains calories and lactose that trigger an insulin response.
Bulletproof Coffee	Breaks Fast	Contains calories from added fats, ending a true fast.
Black Coffee with Artificial Sweeteners	Controversial	While zero-calorie, may trigger cravings or an insulin response in some; best to avoid for a strict fast.

Conclusion

Plain black coffee, regular or decaf, is generally permissible while fasting as it typically doesn't break the fasted state due to its low calorie count. Adding caloric items like milk, sugar, or cream should be avoided. Coffee can support fasting by suppressing appetite and boosting energy, but moderation and hydration are key. Consult a healthcare professional with health concerns. Additional health and diet information is available from {Link: Johns Hopkins Medicine https://www.hopkinsmedicine.org/health/wellness-and-prevention/intermittent-fasting-what-is-it-and-how-does-it-work}.

Frequently Asked Questions

No, even a small splash of milk, whether dairy or plant-based, contains calories and lactose (milk sugar) that will trigger an insulin response, effectively breaking your fast.

As long as it is plain instant coffee without any added sugars or flavorings, it will not break a fast. It has the same negligible calorie count as brewed black coffee.

This is a debated topic. While zero-calorie sweeteners like stevia don't add calories, the sweet taste can cause a neurological response that might interfere with fasting goals like autophagy. For a strict fast, it's best to avoid them.

Coffee is generally known to be an appetite suppressant due to its caffeine content, which helps many people manage hunger. However, individual reactions vary, and some may find it irritates their stomach on an empty stomach.

Experts typically recommend limiting your intake to 2-4 cups (up to 400 mg of caffeine) per day. Excessive consumption can lead to side effects like jitters or anxiety.

Yes, bulletproof coffee breaks a fast. The butter and MCT oil in this drink contain a significant number of calories, ending the fasted state.

Yes, a pinch of zero-calorie spices like cinnamon, nutmeg, or unsweetened cocoa powder can be added to your black coffee to enhance flavor without breaking your fast.