Any food or drink containing significant calories breaks a fast. Zero-calorie drinks like water, black coffee, and plain tea are generally acceptable during a fasting window. If you are wondering what breaks a fast, the simple rule is to avoid anything that requires your body to process energy until your eating window begins.
Weight management, improved energy, and mental focus are among the reasons people explore intermittent fasting. Fasting simply involves the controlled consumption of food over specific periods. For anyone intending to embark on this practice, understanding the guidelines is the first step.
The answer to what breaks a fast will vary depending on the type of fasting you are following and for what purpose. Some guidance suggests that drinking a specific type and quantity of coffee, tea, and certain zero-calorie additions may not significantly affect a fast.
Every fasting experience is personal. What you can consume during a fast depends on your specific protocol and individual health. Speak with a healthcare provider before starting any fasting regimen.
When we wake up in the morning, we usually look for our first meal of the day. This means we have been fasting from the moment we finished our dinner the previous night. Once you eat your morning meal, you have successfully ended your fasting window. An intermittent fasting diet involves going without food at planned intervals (1), and there are various ways to approach this practice.
There are different types of intermittent fasting, depending on the goals and health status of the person involved. Finding the right intermittent fasting diet plans depends on what fits best into your daily schedule.
A 12-hour fast
This type is often the most accessible option for beginners. You fast for 12 hours per day. You might choose to stop eating after dinner at 8 p.m. and end the fast by eating breakfast at 8 a.m. the next day. This allows your body to rest overnight.
A 16-hour fast
During this type of fast, you eat within an 8-hour window. A common approach to this is to finish dinner at 7 p.m. and wait until 11 a.m. the next day to eat again. You then consume your meals between 11 a.m. and 7 p.m.
A 5:2 fast
This method involves eating normally for five days of the week. On the remaining two days, you reduce your food intake. A common fasting diet for women on this plan involves staying within a 500-calorie limit, while men often stay within a 600-calorie limit on those two days.
Alternate-day fasting
There are various approaches to this method. The most common one involves pausing food intake for a full day and then getting back to your normal eating routine once the 24 hours have elapsed.
‘Skipping meals’ fast
This approach involves choosing to skip either breakfast, lunch, or dinner. It is a flexible method that most individuals engage in since it does not require dramatic changes or drastic restrictions.
A 20-hour fast
During a 20-hour fast, you avoid food for 20 hours of the day. You consume all your meals within the remaining four hours. If you want to try this method, you should consult a healthcare provider, as longer periods without food can be demanding on the body.
| Type | Fasting Period | Eating Window | Best For |
|---|---|---|---|
| 12-hour fast | 12 hours | 12 hours | Beginners looking for a gentle start |
| 16:8 method | 16 hours | 8 hours | Those wanting a structured daily routine |
| 5:2 fast | 2 days (reduced calories) | 5 days | People who prefer weekly flexibility |
| Alternate-day | 24 hours (every other day) | 24 hours | Individuals seeking intermittent longer breaks |
| Skipping meals | Varies | Varies | People with unpredictable daily schedules |
| 20-hour fast | 20 hours | 4 hours | Experienced individuals seeking a challenge |
Many people explore an intermittent fasting diet for a variety of reasons beyond simply changing when they eat. Some research has explored associations between intermittent fasting and various health markers. These include metabolic measures such as blood glucose and insulin patterns, cardiovascular markers, and inflammatory indicators.
Individual responses vary greatly. Findings are an active area of ongoing study, and researchers continue to explore how different intermittent fasting diet plans affect the body over time.
| Area of Research | What Some Studies Explore | Research Status |
|---|---|---|
| Metabolic Markers | How fasting affects blood glucose and insulin patterns | Ongoing research shows varying individual responses (2) |
| Cardiovascular Markers | Associations between fasting and blood pressure or lipid profiles | Some studies note changes, but long-term data is still developing (3) |
| Cellular Processes | The role of fasting in triggering autophagy (cellular cleanup) | Widely studied in models; human research is expanding (4) |
| Cognitive Function | Connections between fasting periods and mental focus or clarity | Many people report improved focus, though clinical studies are mixed (5) |
| Inflammation | How eating windows might influence inflammatory indicators | Early research suggests potential associations for some individuals (7) |
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Once you consume anything that supplies enough calories to fuel your body, you have ended your fasted state. To this end, there are specific foods and drinks you can consume while breaking a fast remains off the table.
If you are incorporating intermittent fasting water is your best option. Water is a calorie-free drink, so you can enjoy it throughout your fasting window. But it is not the only drink that fits into a fasting routine. Some guidance suggests that certain types of coffee, tea, and zero-calorie additions may not significantly affect the fasted state.
You should hold off on sodas because they contain sugar and empty calories. Diet sodas should also be approached with caution during your fast, as they can sometimes influence your appetite.
Avoid alcoholic beverages completely during this period, as their caloric content will break your fast and likely increase your hunger levels. Zero calorie foods and fasting drinks are your main tools during the fasting window.
| Item | Breaks Fast? | Notes |
|---|---|---|
| Water | No | Plain water is always acceptable and encouraged. |
| Sparkling Water | No | Unflavored sparkling water contains no calories. |
| Black Coffee | No | Contains negligible calories; generally acceptable. |
| Plain Tea | No | Herbal, green, or black tea without additives is fine. |
| Lemon Water | No | A squeeze of lemon has minimal calories and is widely accepted. |
| Apple Cider Vinegar (ACV) | No | A small amount diluted in water is usually fine. |
| Diet Soda | Debated | Calorie-free, but may trigger cravings for some people. |
| Stevia | No | A zero-calorie sweetener, though individual responses vary. |
| Sucralose | Debated | Zero calories, but some research explores insulin responses. |
| Aspartame | Debated | Zero calories; accepted by some, avoided by others. |
| Saccharin | Debated | Zero calories, but may affect insulin in certain individuals. |
| Milk | Yes | Contains calories, carbohydrates, and proteins. |
| Cream | Yes | High in calories and fats. |
| Sugar | Yes | Pure carbohydrate; immediately breaks a fast. |
| Bone Broth | Yes | Contains calories and protein, ending the strict fasted state. |
| Flavored Coffee | Yes | Syrups and flavorings almost always contain calories. |
| Protein Shake | Yes | High in calories and protein; used during the eating window. |
| BCAA Supplements | Yes | Amino acids trigger a metabolic response. |
| Collagen | Yes | Contains protein and calories. |
| Gummy Vitamins | Yes | Often contains sugar and calories. |
| Alcohol | Yes | High in empty calories and disrupts metabolic processes. |
Selecting the right fasting food for your eating window is crucial for maintaining your energy. Below is a look at foods suitable for an intermittent fasting diet.
Protein supports muscle maintenance during a fasting protocol and contributes to satiety during eating windows (8, 9). When planning your intermittent fasting meals, prioritizing protein can help you feel fuller for longer. Options include eggs, seafood, soy, beans, legumes, fish, poultry, milk, yogurt, and cheese.
Carbohydrates supply the body with energy (10). You can source them from different foods, focusing on fibers and complex starches. Great examples include brown rice, apples, kidney beans, bananas, oats, sweet potatoes, berries, carrots, broccoli, almonds, and chickpeas. These options provide a steady release of energy rather than a quick spike.
Healthy fats from sources like avocados, nuts, and olive oil are associated with nutritional quality and satiety during eating windows (9). Including these fats in your meals helps round out your diet. Examples of healthy fats include whole-fat yogurt, whole eggs, cheese, dark chocolate, extra virgin olive oil, and salmon.
Other foods to include in your eating window are vegetables like lettuce, celery, tomatoes, cucumbers, and fermented options like sauerkraut and tempeh. Make sure to drink plenty of water. It is a good practice to minimize your intake of refined grains, highly processed meats, and soft drinks.
| Food Category | Examples | Why It Helps During Fasting |
|---|---|---|
| Lean Proteins | Chicken, fish, tofu, eggs | Supports muscle maintenance and keeps you feeling full (9). |
| Complex Carbs | Oats, sweet potatoes, brown rice | Provides steady, long-lasting energy for the day (10). |
| Healthy Fats | Avocados, olive oil, nuts | Contributes to satiety and overall nutritional quality (9). |
| Fibrous Veggies | Broccoli, leafy greens, carrots | Adds volume to meals and aids digestion (11). |
| Hydrating Foods | Cucumbers, celery, strawberries | Helps maintain hydration levels during the eating window (12). |
Read More: 12 Hour Intermittent Fasting for Weight Loss and other Benefits
If you feel like brewing a cup of coffee in the morning, you will not break your fast if you stick to black coffee. Natural tea without added sugar, sweeteners, or milk is also acceptable. Adding milk, whether skimmed or whole, introduces calories and ends your fast.
Although black coffee is practically calorie-free, monitor your intake so you do not upset your stomach. Some people find that large amounts of caffeine affect hunger levels, which is worth monitoring during a fasting window.
If you want to add flavor to your coffee while fasting, certain spices have negligible energy content. You can occasionally add a pinch of powdered cinnamon to your cup without significantly altering your fasted state. Exploring different fasting drinks can keep your routine interesting without adding calories.
Artificial sweeteners provide a sweet taste similar to sugar or honey but without the standard caloric load. To know what artificial sweetener breaks a fast, you must consider its specific composition and how your body reacts to it.
Some approaches suggest that certain zero-calorie artificial sweeteners (such as saccharin, aspartame, and sucralose) may not significantly affect the fasted state, though some research suggests sweeteners may trigger an insulin response in some individuals (12). You should check the labels carefully. Sugars of alcohol with a higher caloric content, such as sorbitol, maltitol, and xylitol, provide enough energy to break your fast.
A keto diet focuses on consuming low-carbohydrate, higher-fat foods. While you rely mostly on energy from fats, you also consume moderate protein and heavily restrict carbohydrates. When you follow a keto diet, you avoid high-carbohydrate foods, sugary drinks, and alcohol (13).
While keto aims at changing the types of foods you eat, intermittent fasting focuses on structuring when you eat. The two methods have a lot in common, as both restrict certain items to encourage the body to use stored energy. They can easily work together. A zero-calorie drink that works for intermittent fasting will generally also align with a keto routine.
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When considering your first meal after fasting, progress slowly. Take note of the following points before eating after a longer fasting window:
Drink enough liquid to keep yourself hydrated before reaching for solid food. Hydration prepares your digestive system for the upcoming meal.
When you are ready to eat, start with something gentle on the stomach. A simple cucumber salad with chopped tomatoes and parsley is a great option. Heavy or highly processed foods can cause discomfort.
Lean proteins like fish or poultry are commonly included in the first meal after a fast, as they provide nutrients the body may have been without. Eat slowly and listen to your body’s fullness cues.
Non-starchy vegetables can be added to your plate. Options like green beans, cabbage, cauliflower, eggplant, and greens work well. You can cook them lightly in healthy fats like olive oil.
Eat something more substantial only after your body has comfortably processed the initial lighter foods. Pacing yourself helps avoid digestive discomfort.
| Food/Drink | Why to Avoid After Fasting |
|---|---|
| Sugary snacks | Can cause a rapid spike and subsequent drop in blood glucose. |
| Greasy fast food | Heavy fats can be difficult to digest on an empty stomach. |
| Large portions of meat | Requires significant digestive energy, which may cause discomfort. |
| Refined carbohydrates | White bread or pastries digest quickly and offer little nutritional value. |
| Carbonated sugary drinks | Can cause bloating and introduce empty calories immediately. |
Every fasting experience is personal. What you can consume during a fast depends on your specific protocol and individual health. Speak with a healthcare provider before starting any fasting regimen.
Read More: Does Coffee Break A Fast: Science-Backed Take On Coffee And Its Effect On Fasting
Most zero-calorie artificial sweeteners (such as stevia, saccharin, sucralose, and aspartame) technically contain negligible calories and are generally considered not to break a fast from a caloric perspective.
However, some research suggests sweeteners may trigger an insulin response in certain individuals (12), which is an area of ongoing debate. You may choose to avoid them if you prefer a strict approach.
Technically, any calorie intake breaks a fast from a strict physiological perspective. Most intermittent fasting approaches use a practical threshold, and many practitioners consider fewer than 50 calories to be unlikely to significantly affect the fasted state for most people, though individual responses vary. It is usually best to aim for zero calories during your fasting window to keep things simple.
Plain water, plain sparkling water, black coffee (no milk or sugar), plain herbal or green tea, and plain electrolyte water (no sweeteners) are all widely considered acceptable during a fasting window by most approaches.
These items provide hydration or mild stimulation without delivering metabolic energy. You can review the master table in this article for a comprehensive breakdown of common items.
There is no single defined duration that guarantees specific results, as research findings vary by outcome and individual. Most studied approaches range from 12 to 24 hours, with the 16:8 method being the most widely researched option (14). Finding a duration that fits comfortably into your lifestyle is generally more important than pushing for extreme hours.
Research does not clearly identify a single fasting window as optimal for reducing belly fat specifically. The 16:8 method is the most widely studied and commonly used framework. The most important factor is your adherence to the routine and your overall nutritional balance during the eating window.
Common signs that many people associate with ketosis include reduced appetite after the initial adjustment, a distinct breath odor, increased thirst, and initial fatigue followed by improved energy for some people (15).
Individual experiences vary widely when transitioning into this metabolic state. Staying hydrated and monitoring how you feel is important during this adjustment period.
Understanding what breaks a fast can make intermittent fasting feel much more straightforward. In most cases, foods and drinks with meaningful calories break a fast, while options like water, plain tea, and black coffee are often considered acceptable during a fasting window. The details can vary based on your approach, your goals, and how strict you want to be.
Every fasting experience is personal. What you can consume during a fast depends on your specific protocol and individual health. Speak with a healthcare provider before starting any fasting regimen.
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