Does Coffee Break Intermittent Fasting Dr. Berg's Perspective?

January 6, 2026 •

3 min read

According to Dr. Eric Berg, consuming plain black coffee does not break an intermittent fast because it contains negligible calories and does not trigger an insulin spike. However, he emphasizes that the key to staying in a fasted state depends entirely on what is added to your morning cup.

Quick Summary

Dr. Berg confirms that plain black coffee is generally acceptable during intermittent fasting as it avoids an insulin response. The fasting state is broken by caloric additives, especially sugar and milk, so additions must be chosen carefully to maintain the metabolic benefits of fasting.

Key Points

Plain black coffee is safe: Black coffee with no additives contains negligible calories and won't break a fast according to Dr. Berg.
Caloric additives break the fast: Adding milk, sugar, or high-calorie creamers will spike insulin and end the fasted state.
Beware of artificial sweeteners: Dr. Berg advises against most artificial sweeteners like sucralose, which can trigger an insulin response and affect gut health.
Use natural zero-calorie sweeteners: Stevia and monk fruit are considered acceptable for weight loss fasting, but check for added fillers.
Small amounts of fat may be okay: On a 'Healthy Keto' plan, a small amount of fat like butter or MCT oil in bulletproof coffee is permissible for energy and satiety, but may disrupt autophagy.
Moderation is important: Excessive caffeine can lead to negative side effects like jitters or sleep disruption.
Hydration is still key: Drink plenty of plain water alongside coffee to stay hydrated during your fast.

Understanding the Fasting State

Before diving into coffee, it's essential to understand the core principle of intermittent fasting, particularly from Dr. Berg's perspective: it's about keeping insulin levels low. When you consume anything that raises your insulin, you exit the fasting state, effectively stopping the beneficial fat-burning and cellular repair processes like autophagy. The goal is to minimize caloric and carbohydrate intake during your fasting window to maintain this low-insulin state and maximize results.

The Role of Plain Black Coffee

For most people practicing intermittent fasting, plain black coffee is completely safe and beneficial. Here's why:

Negligible Calories: A standard cup of black coffee contains only about 3 calories, an amount too small to trigger a significant metabolic change.
No Insulin Response: Without added sugar or cream, black coffee does not cause an insulin spike, allowing your body to remain in a fasted, fat-burning state.
Appetite Suppression: The caffeine in coffee can act as a natural appetite suppressant, making it easier to extend your fasting window and control hunger.
Enhanced Focus and Metabolism: Caffeine can also boost energy levels and sharpen mental clarity, and it has a thermogenic effect that can slightly increase your metabolic rate.

Coffee Additives: The Line Between Fasting and Feasting

This is where Dr. Berg and other experts draw a firm line. Any ingredient that contains sugar, protein, or significant calories will break your fast. You must be vigilant about what goes into your coffee to avoid sabotaging your progress.

Forbidden Additives According to Dr. Berg

Sugar and Syrups: Any form of sugar or sweetened syrup will immediately spike your blood glucose and insulin levels, breaking the fast.
Milk and Creamer: Milk contains lactose (a sugar) and protein, which both stimulate insulin. Flavored creamers are even worse due to added sugars and artificial ingredients.
Artificial Sweeteners: Dr. Berg advises against most artificial sweeteners like Splenda (sucralose). Even if they are calorie-free, they can trigger an insulin response and affect gut health, disrupting metabolic benefits and potentially causing cravings.

What About Fats in Coffee? (The Keto Exception)

For those following a ketogenic diet alongside intermittent fasting (which Dr. Berg refers to as "Healthy Keto®"), the rules are slightly different. He notes that adding a small amount of pure fat, such as grass-fed butter or MCT oil, in the form of "bulletproof coffee," can be acceptable. This is because pure fats do not trigger an insulin spike. However, it's important to understand the nuance:

For Weight Loss: A small amount of added fat won't kick you out of the fat-burning state for weight loss. It can provide energy and curb hunger.
For Autophagy: If your primary fasting goal is autophagy (cellular cleanup), introducing any calories, even from pure fat, will likely interrupt the process. For deep, pure fasting, stick to plain liquids.

Comparison of Coffee Types and Fasting Impact


Coffee Type	Additives	Fasting Friendly? (Dr. Berg's View)	Reason
Black Coffee	None	Yes	Minimal calories, no insulin spike.
With Milk/Sugar	Milk, sugar, flavored creamer	No	Triggers insulin response, breaking the fast.
Bulletproof Coffee	Butter, MCT Oil	Yes (for Healthy Keto)	Pure fats don't spike insulin, provides energy.
With Artificial Sweetener	Splenda, aspartame	No	May trigger insulin response and create cravings.
With Natural Sweetener	Stevia, monk fruit	Yes (in moderation)	Zero-calorie, does not significantly affect blood glucose or insulin.

How to Incorporate Coffee into Your Fasting Routine

Moderation is Key: Don't overdo it. Excessive caffeine, especially on an empty stomach, can cause jitters, increased heart rate, or digestive issues for some individuals.
Listen to Your Body: Pay attention to how coffee affects you personally. If it causes discomfort or negatively impacts your sleep, you may need to reduce your intake or drink it earlier in the day.
Stay Hydrated: Remember that coffee is a diuretic. It's crucial to also drink plenty of plain water during your fast to stay hydrated.

Conclusion

For those wondering, "Does coffee break intermittent fasting Dr. Berg?", the answer is clear and depends on how you take it. Plain black coffee is perfectly acceptable and can even enhance your fasting experience by boosting energy and suppressing appetite. However, adding caloric ingredients like sugar and milk will break your fast. While Dr. Berg permits small amounts of fat for those on a keto diet, the purest form of fasting requires sticking to non-caloric liquids. By following these clear guidelines, you can enjoy your coffee and maximize the benefits of intermittent fasting.

Visit Healthline for more on combining coffee and fasting.

Frequently Asked Questions

Dr. Berg states that plain black coffee is acceptable during an intermittent fast because it is extremely low in calories and does not trigger an insulin spike, allowing the body to remain in a fasted state.

Yes, according to Dr. Berg, adding milk, creamer, or any other calorie-containing liquid to your coffee will break a fast. These additives contain protein and sugar that cause an insulin response, interrupting the metabolic benefits of fasting.

Natural zero-calorie sweeteners like stevia and monk fruit are generally okay in moderation for fasting related to weight loss, as they do not significantly impact insulin levels. However, Dr. Berg warns against most artificial sweeteners, which can have negative metabolic effects.

Dr. Berg considers bulletproof coffee acceptable for those on a 'Healthy Keto' plan, as the pure fats do not spike insulin. However, this is not a pure fast and will interrupt some fasting benefits like autophagy.

Dr. Berg recommends moderation, as too much caffeine can cause side effects like jitters, anxiety, and sleep issues. The exact amount varies by individual tolerance, so it's important to listen to your body.

Yes, caffeine has a natural appetite-suppressing effect, which can make it easier to manage hunger and extend your fasting window.

Plain black coffee does not negatively impact ketosis. In fact, some evidence suggests that caffeine may even enhance ketone production. However, adding carbs or sugar will immediately disrupt ketosis.