Is there anything I can put in my coffee while intermittent fasting?

December 27, 2025 •

4 min read

Plain black coffee, with approximately 3-5 calories per cup, is generally considered safe during intermittent fasting. Navigating the rules for additives can be tricky. This guide explores ingredients that can be added to coffee without compromising fasting goals, from calorie-free flavor enhancers to options for specific fasting protocols.

Quick Summary

This article explores coffee additives safe for intermittent fasting, including spices and zero-calorie sweeteners. It clarifies why caloric creamers and sugar should be avoided to maintain fasting benefits.

Key Points

Black Coffee is Safest: The purest option for intermittent fasting is plain black coffee, as it contains negligible calories and won't break a fast.
Zero-Calorie Sweeteners are an Option: Pure monk fruit and stevia extracts are generally considered safe in moderation, but be wary of commercial blends with added fillers.
Spices Enhance Flavor: Minimal additions of cinnamon, nutmeg, or cardamom add flavor without introducing calories or breaking your fast.
Avoid Sugars, Milk, and Syrups: Any ingredient with sugar or dairy will trigger an insulin response and should be avoided during the fasting window.
Understand "Dirty" Fasting: Additives like MCT oil and butter are used by some fasters, particularly on a ketogenic diet, but they contain calories and will break a clean fast.
Read Labels on Creamers: Many "sugar-free" creamers contain other caloric ingredients that can interfere with your fast, so always check the nutritional information.

What is a "Clean" Fast?

A "clean" fast means consuming only water and other non-caloric beverages that don't trigger an insulin response. The goal is to keep insulin levels low, encouraging the body to burn stored fat (ketosis) and support autophagy, the body's cellular "self-cleaning" process. Even small amounts of sugar, milk, or other caloric additives can prompt an insulin release, effectively breaking the fast.

The Golden Rule: Stick to Black Coffee

The simplest and safest option for coffee consumption during intermittent fasting is to drink it black. This means no sugar, honey, milk, or cream. The following sections provide alternatives.

Fast-Friendly Coffee Additives

Zero-Calorie Sweeteners

Zero-calorie sweeteners are a popular solution for those who can't stand unsweetened coffee. Some debate exists on whether the sweet taste itself could trigger a metabolic response or cravings. For most, however, a small amount of a high-purity, non-nutritive sweetener is unlikely to have a significant impact.

Monk Fruit: Derived from monk fruit, this natural, zero-calorie sweetener does not impact blood glucose or insulin levels. Be cautious of commercial blends that may include erythritol or other fillers, which might affect certain fasting goals.
Stevia: Extracted from the Stevia rebaudiana plant, pure stevia extract is another calorie-free, natural sweetener. Check for fillers in powdered blends. Stevia is generally well-tolerated and does not seem to affect gut microbiota.
Erythritol: A sugar alcohol with virtually no calories, erythritol is also considered safe for most fasting protocols as it is not metabolized in a way that significantly impacts blood sugar.

Spices for Flavor

Natural spices are an excellent choice if sweeteners are not preferred. They are low-calorie and don't affect insulin levels when used in small amounts.

Cinnamon: A small sprinkle adds a warm, spicy flavor without calories. It may help with blood sugar regulation, complementing fasting benefits.
Nutmeg and Cardamom: A dash of nutmeg or cardamom can introduce a different flavor profile, offering variety.

Healthy Fats (with a Caveat)

Some intermittent fasters, particularly those following a ketogenic diet, incorporate fats into their coffee. This practice is known as "dirty fasting" because it introduces calories and technically breaks a "clean" fast, but proponents argue it doesn't significantly spike insulin.

MCT Oil: Medium-chain triglyceride (MCT) oil is a type of fat rapidly converted into ketones for energy. While it contains calories (roughly 130 per tablespoon), it can help suppress appetite and provide a mental boost without spiking insulin dramatically.
Grass-fed Butter or Ghee: Combining coffee with grass-fed butter or ghee results in a "Bulletproof coffee". Like MCT oil, this adds fat-based calories but is debated for its effect on a clean fast, as it still provides fuel to the body.

Comparison of Coffee Additives During Intermittent Fasting


Additive	Fasting-Friendly Status	Primary Impact	Best For	Considerations
Black Coffee	Ideal	Minimal	Strict fasts, weight loss, autophagy	Can be challenging for those used to sweet coffee.
Pure Stevia/Monk Fruit	Generally safe	None (low calorie)	Weight loss, calorie restriction	Watch for additives in commercial blends; may trigger cravings in some.
Cinnamon/Spices	Safe	Minimal	Flavor enhancement	Use sparingly; can be added without concern.
MCT Oil	"Dirty" fast	Provides fat-based calories	Keto/fat-burning focus	Breaks a clean fast; high in calories.
Heavy Cream (small)	"Dirty" fast	Small amount of fat calories	Less strict fasts	Still breaks a clean fast; higher impact than MCT oil.
Sugar, Honey, Syrups	Breaks fast	Triggers insulin spike	None	Completely breaks the fasting state.

What to Absolutely Avoid

Certain common coffee additions will immediately break a fast due to their caloric and carbohydrate content, triggering an insulin response and halting the fat-burning and autophagy processes. These include:

Sugar and Syrups: Any form of sugar, including honey, maple syrup, and flavored syrups, is off-limits.
Milk and Cream: Dairy contains lactose, a form of sugar, which will spike insulin. This includes cow's milk and most plant-based milks like oat or sweetened almond milk.
Standard Creamers: Most coffee creamers, even many marketed as "sugar-free," contain oils and other ingredients that provide calories and can break a fast. Always check the nutrition label.
Collagen and Protein Powders: These additives contain protein and calories, which will end your fast.

Finding Your Balance

The best approach depends on personal fasting goals. Sticking to black coffee is the safest bet for maximum autophagy and metabolic benefits. A minimal amount of zero-calorie sweetener or a dash of spice is likely fine for those focused on weight loss and who need a little flavor to get through the fasting window. It is wise to consult a healthcare professional, especially if pre-existing health conditions like diabetes exist. Understanding how different additives affect the body allows informed decisions that support health goals. For more information on the principles of intermittent fasting, a great resource is Johns Hopkins Medicine.

Frequently Asked Questions

Yes, even a small splash of milk or cream contains lactose (milk sugar) and calories, which can trigger an insulin response and break a clean fast.

While calorie-free, artificial sweeteners like Splenda (sucralose) are debated. Some studies suggest they may cause a minor insulin response or increase cravings, potentially dampening the benefits of a fast.

No, Bulletproof coffee technically breaks a fast because it contains a significant number of calories from fat. While it won't spike insulin like sugar, it provides fuel that takes you out of the fasted state.

Most sugar-free creamers contain oils and other additives with calories. Always check the label, as these will likely break your fast. Stick to black coffee for best results.

A small sprinkle of cinnamon is generally considered safe and will not break a fast. It contains a negligible amount of calories and can add flavor without concern.

A "clean" fast involves consuming only non-caloric beverages like water and black coffee. A "dirty" fast allows for minimal calorie intake (often less than 50) from fat sources, which technically breaks the fast but aims to avoid an insulin spike.

To improve the taste of black coffee, try using a higher-quality bean, adding a pinch of salt to reduce bitterness, or experimenting with spices like cinnamon or nutmeg. Pure zero-calorie sweeteners like stevia can also help if used sparingly.