What Breaks a Fast?

April 9, 2025

Intermittent fasting is a highly effective weight-loss tool with various other impressive health benefits. However, many people practicing fasting are unsure of what breaks a fast and what doesn’t.

Discover what foods and beverages you can consume during fasting without interfering with fat-burning or ketosis.

What will break a fast?

What will break a fasting period depends on the exact type of fast you are practicing and how you define breaking a fast.

For example, dry fasting is a strict fast that avoids the intake of all foods and beverages, including water, and consuming any fluids or calories breaks this type of fast.

In contrast, water fasting permits hydration with plain water. However, eating or drinking anything else, including beverages with zero calories, will technically break this fasting practice.

An intermittent fasting plan is a somewhat more flexible approach to time-restricted eating. It allows the intake of certain foods and beverages as long as they don’t raise blood sugar levels and contain very few calories.

Fasting is characterized by calorie restriction, which induces a metabolic state that shifts the body to using stored energy as a fuel source. This promotes weight loss and releases ketones, a metabolic by-product of fat burning that serves as an alternative energy source.

When ketones begin to fuel your cells, your body enters the metabolic state of ketosis.

Not only is ketosis linked to weight loss, but it also supports hormonal balance, promotes metabolic health, increases energy, and enhances cognitive functions.

Any food or beverage that raises blood sugar levels will trigger the release of insulin, a crucial hormone that regulates blood sugar levels. However, insulin also directly inhibits fat-burning and counteracts the health benefits of fasting and ketosis.

This explains why most people refer to breaking a fast when consuming anything that causes an insulin response, as opposed to ingesting any foods or beverages.

What triggers insulin release

Carbohydrates and sugars cause spikes in blood sugar and insulin levels and should be avoided when intermittent fasting, as they can quickly break your fast.

“While protein doesn’t cause as significant blood sugar fluctuations as carbs and sugar, it does stimulate insulin release,” explains Dr. Berg. “To maintain fat-burning and ketosis during your fasting window, it’s important to avoid protein-containing food or drinks.”

While fat doesn’t significantly impact insulin levels and won’t interfere with ketosis, eating too much fat during fasting periods can also break a fast due to its calorie content.

Evidence published in EMBO Molecular Medicine shows that consuming more than a few calories triggers complex metabolic pathways that disrupt the fasting state and interfere with fat burning.¹

How many calories you can consume without breaking a fast depends on your metabolic flexibility and the fat, carbohydrate, and protein content of the food or beverage you consume.

Watch the video below to learn more about what will break a fast and what won’t.

What foods and drinks can you have while fasting?

There are various beverages and a few select foods that won’t raise blood sugar or insulin levels that you can consume while fasting.

Here are fasting-friendly drinks you can enjoy during your fasting window:

Plain or carbonated water
Black coffee
Black, green, and herbal tea
Diluted apple cider vinegar

Adding small amounts of lemon juice to your water, tea, or diluted apple cider vinegar drink won’t interfere with fat-burning and may help enhance the weight loss effects of fasting.

Research published in Nutrition Research found that lemons contain various phytochemicals that promote metabolic health, support fat-burning, and help maintain a healthy body weight.²

If you prefer your coffee or tea with a little sweetness, low-carb sugar alternatives such as erythritol, monk fruit, and stevia contain minimal calories and are fast-friendly.

In addition, consuming small amounts of healthy fats such as coconut oil, grass-fed butter, heavy cream, or ghee while fasting provides energy and may curb cravings. This can help achieve longer periods of caloric restriction, maximizing the health benefits of fasting.

Many individuals who practice fasting drink bulletproof coffee, also known as keto coffee, during fasting periods.

Bulletproof coffee combines black coffee, medium-chain triglycerides (MCTs), and butter. It offers a quick energy source and helps with appetite control without raising insulin levels, which explains why bulletproof coffee won’t break a fast.

However, it’s important to remember that too many calories can disrupt the fasting state, and consuming bulletproof coffee in moderation is crucial while fasting.

What you should avoid while fasting

To maintain a metabolic fasting state, it’s important to avoid any foods or beverages that contain more than a few calories and those that can raise blood sugar or insulin levels.

Bone broth is often mentioned as a fasting-friendly option due to its low carbohydrate content. However, it contains collagen, a type of protein that can break a fast if consumed excessively.

While it may be tempting to sip a diet soda during fasting, this isn’t recommended, as artificial sweeteners can stimulate insulin release and increase cravings for sugary foods.

In addition, research published in Nutrients found that synthetic sweeteners such as aspartame, which are often used to sweeten diet sodas and low-calorie food, may pose significant long-term health risks.³

According to this study, aspartame has been associated with hormonal imbalances, increased risk of cancer, neurodegenerative disorders, skin problems, and dysregulated immune responses.

Although a cup of black coffee won’t break a fast, it’s vital to avoid excessive intake. Consuming too much caffeine can trigger the body’s stress response, which involves cortisol release and activates gluconeogenesis.

Gluconeogenesis is a metabolic process that converts proteins into glucose, thereby increasing blood sugar concentration and stimulating insulin release, which will break a fasting state.

Healthy ways to break a long fast

Reaching your health goals with fasting doesn’t just require achieving prolonged fasting periods but also depends on how you break your fast and your overall dietary choices.

Avoid breaking your fast with heavily processed foods, sugars, or refined carbs. These foods cause rapid blood sugar and insulin spikes, putting your body immediately into a fat-storage mode, directly counteracting the benefits of caloric restriction.

Instead, opt for nutrient-dense foods rich in healthy fats. Limiting carbs while providing the body with fats helps avoid blood sugar fluctuations, prolonging the fat-burning effects of fasting and ketosis.

One of the best dietary patterns to combine with intermittent fasting is a nutritious low-carb diet such as Healthy Keto®.

Healthy Keto focuses on highly nutritious foods while limiting carbohydrates. This helps replenish nutrient levels and maintain ketosis even after breaking your fast.

Following a low-carb diet and practicing intermittent fasting is an excellent strategy for supporting metabolic balance, maintaining a healthy body weight, and enhancing overall health and well-being.

Some individuals can experience digestive issues such as bloating, belching, and diarrhea after breaking a fast.

Refeeding with easy-to-digest soups, bone broth, cooked vegetables, or full-fat yogurt can ease the transition into your eating window without negatively affecting the digestive system.

Key takeaways

Knowing what breaks a fast and what doesn’t is vital to maintaining a fasted state and reaping the impressive benefits of prolonged caloric restriction.

While consuming any foods or beverages technically breaks fast, drinking coffee, tea, and plain water and eating small amounts of healthy fats won’t interfere with the metabolic fasting state or disrupt fat-burning.

In addition, combining intermittent fasting with a nutritious low-carb diet such as Healthy Keto helps maintain ketosis after breaking your fast, maximizing the profound health advantages of caloric restriction.

FAQ

1. Will five calories break a fast?

It’s unlikely that five calories will break a fast. However, it does depend on the food or beverage consumed. Especially carbohydrates and sugars can quickly break a fast, even if consumed in small amounts.
Foods or drinks containing carbs and sugars raise blood sugar and insulin levels, which inhibits fat burning and breaks the metabolic fasting state.

2. Does chewing gum break a fast?

Chewing gum sweetened with sugar or artificial sweeteners can break a fast by stimulating digestive processes and triggering insulin release.
However, sugar-free gum with minimal calories is unlikely to impact blood sugar or insulin balance and won’t break a fast.

3. What foods do not break a fast?

Although consuming any food will technically break a fast, healthy fats such as coconut oil, grass-fed butter, or ghee won’t raise blood sugar levels and can be consumed while fasting to provide energy and curb hunger.
It’s important to remember that consuming too many calories triggers digestive processes and insulin release, and it’s crucial to consume only small amounts of high-fat foods to maintain the fasting state.

4. What will knock you out of a fasting state?

Any food or drink that contains too many calories or triggers insulin release will knock you out of a fasting state. Especially carbohydrates, sugars, and protein can stimulate an insulin response and should be avoided during your fasting period.

5. What foods should I eat to break a fast?

It’s important to break a fast with easy-to-digest, nutrient-dense foods to replenish essential vitamins and minerals while minimizing the risk of digestive issues. Bone or vegetable broth, soups, and full-fat yogurt are excellent options to break a fast.
It’s also recommended to refeed with low-carb foods and consume plenty of healthy fats. This helps avoid blood sugar and insulin spikes, which can directly counteract the metabolic benefits of fasting.