What Breaks a Fast? What You Can (and Can't) Have While Fasting
Updated: Nov 2
The quick answer: Technically, anything with calories breaks a fast. Water, sparkling water, black coffee and plain tea do not. A splash of heavy cream, a little butter or ghee, lemon water or bone broth will break a strict "clean" fast, but they have very little effect on insulin, so many people use them as fasting aids to go longer with less hunger.
New to fasting? Start with my Beginner's Guide to Intermittent Fasting, or book a free consultation with me.
What breaks a fast? At a glance
Food or drink | Breaks a fast? | Coach Theah's take |
Water (still or sparkling) | No | Drink plenty! It's the foundation of every fast |
Black coffee | No | Fine for most people; skip it if it makes you jittery |
Plain tea (green, black, herbal) | No | Great for calming hunger waves |
Water infused with fruit or herbs | No (trace amounts) | Cucumber, mint, berries or citrus slices for flavor |
Lemon or lime water | Technically, barely | Minimal impact; fine as a fasting aid |
Heavy cream in coffee or tea | Yes, minimally | Fasting aid: limit to 2 tablespoons |
Butter or ghee in coffee | Yes, minimally | Fasting aid: limit to 2 to 3 teaspoons |
Bone broth | Yes, minimally | Fasting aid: great for hunger and minerals |
Electrolytes (no sugar) | No | Salt, magnesium and potassium help prevent headaches |
Artificial sweeteners and diet soda | Avoid | Can trigger cravings and an insulin response in some people |
Gum and anything you chew | Avoid | Chewing kick-starts digestion and hunger |
Milk, lattes, creamers with sugar | Yes | Too much sugar and protein; save for your eating window |
Protein powder and BCAAs | Yes | Protein spikes insulin and ends your fast |
Juice, smoothies, gummy vitamins | Yes | Sugar ends your fast quickly |
What doesn't break a fast
These have no or almost no calories and won't raise insulin. Enjoy them throughout your fast:
Water, still or sparkling. Aim to drink more than usual, since you're not getting water from food.
Black coffee. It can even help curb hunger. Limit it if you feel anxious or jittery.
Plain tea, green, black or herbal, hot or iced.
Infused water with fresh fruit slices or herbs for flavor.
Fasting aids: they technically break a fast, but help you go longer
If a little something helps you fast longer and feel better, it's often worth it. These have a limited impact on insulin:
Lemon or lime water
Heavy cream in your coffee or tea (limit to 2 tablespoons)
Butter or ghee in your coffee or tea (limit to 2 to 3 teaspoons)
Bone broth, beef or chicken. Add a little fat if you need it. Here's why bone broth works while fasting.
Using small amounts of fat or calories during a fast is sometimes called "dirty fasting." Learn the pros and cons in What Is Dirty Fasting, and Should You Try It?
Supplements during your fast
Electrolytes: salt, magnesium and potassium. These are the biggest help for headaches, fatigue and dizziness while fasting. Choose sugar-free options.
Glutamine and glycine: some people use small amounts of these amino acids to support their gut and ease hunger during longer fasts. Check with your provider first.
Most other vitamins and supplements are best taken with food during your eating window, especially anything that upsets your stomach or must be taken with a meal.
What to avoid while fasting
Artificial sweeteners. Zero calories, but they can keep sugar cravings alive and may trigger an insulin response in some people.
Anything you chew, including gum. Chewing signals your body to get ready for food.
Gummy multivitamins. They're basically candy.
BCAAs and protein powder. Protein raises insulin and ends your fast.
Supplements with hidden sugar: cane sugar, fruit juice concentrate, pectin or maltodextrin.
Does it depend on why you're fasting?
Yes! If your main goal is weight loss and lower insulin, small fasting aids like cream, butter or bone broth are usually fine if they help you go longer. If you're fasting for gut rest or cellular cleanup (autophagy), a clean fast with only water, black coffee and plain tea is best.
If you need more help: try a fat fast
Struggling to get through a fast? A short fat fast can ease you in, curb cravings and help your body shift into fat-burning mode. Learn how in Fat Fasting 101: The Reset Button Your Body Has Been Craving.
FAQ
Does coffee break a fast?
Black coffee does not break a fast. Adding sugar, milk or sweetened creamer does. A splash of heavy cream breaks a strict fast but has very little effect on insulin.
Does lemon water break a fast?
A squeeze of lemon or lime in water has so few calories that it has almost no effect. It's a great way to add flavor and make fasting easier.
Does creamer break a fast?
Sweetened and flavored creamers do break a fast. Up to about 2 tablespoons of plain heavy cream is a fasting aid many people use with little impact on insulin.
Do electrolytes break a fast?
Sugar-free electrolytes (salt, magnesium and potassium) do not break a fast, and they can help prevent headaches and fatigue.
Does chewing gum break a fast?
Most gum has sweeteners and very few calories, but chewing can trigger hunger and digestion. I recommend skipping it while fasting.
Does bone broth break a fast?
Technically yes, since it has some calories and protein. But a cup of bone broth has little effect on insulin and can help you get through a longer fast with fewer hunger pangs.
Keep learning
Want a fasting plan that works for you?
Book a free 60-minute consultation and we'll find the fasting rhythm, and the fasting aids, that fit your body and your goals.
Disclaimer: This content is for education only and is not medical advice. If you take medication, especially for blood sugar, are pregnant or breastfeeding, or have a history of an eating disorder, talk with your doctor before fasting.
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