What is Allowed to Eat During Intermittent Fasting?

January 9, 2026 •

4 min read

According to a 2019 study published in the journal Nutrients, caffeine consumption during fasting periods can help suppress appetite. This practice, along with other calorie-free liquids, forms the foundation of what is allowed to eat during intermittent fasting, while your body shifts into a fat-burning state.

Quick Summary

Intermittent fasting allows only calorie-free beverages during the fasting window, including water, black coffee, and herbal tea. The eating window should include nutrient-rich, whole foods such as lean proteins, healthy fats, fruits, and vegetables to support weight loss and health.

Key Points

Fasting Window Rules: During the fasting period, consume only zero-calorie beverages such as water, black coffee, and unsweetened tea to avoid breaking the fast.
Eating Window Choices: Focus on nutrient-dense, whole foods during your eating window, including lean proteins, healthy fats, fruits, and vegetables to maximize fasting benefits.
Avoid Sugary Additives: Never add milk, sugar, cream, or caloric sweeteners to your beverages during the fasting window, as these contain calories and can cause an insulin response.
Enhance Fat Burning: Black coffee's minimal calories won't break your fast and can actually enhance fat-burning and suppress appetite, making fasting easier.
Break Fast Gently: When ending your fast, start with easily digestible, nutrient-rich foods rather than a large, heavy meal to avoid digestive upset.
Stay Hydrated: Staying properly hydrated with plain water throughout the fasting window is crucial for managing hunger and preventing side effects like headaches or fatigue.
Consider 'Dirty Fasting' Carefully: While some allow minimal calorie intake (e.g., bone broth), a 'dirty fast' technically breaks a true fast and can limit full metabolic benefits like autophagy.

What Can You Drink During Your Fasting Window?

During your fasting period, the goal is to consume as few calories as possible to maintain a fasted state. This enables your body to switch from burning glucose to burning stored fat, a process known as metabolic switching. Staying hydrated is crucial during this time to manage hunger and prevent dehydration.

The following beverages are generally considered safe and will not break your fast:

Plain Water: This is the most essential and foundational drink during any fast. It is calorie-free and helps keep you hydrated.
Black Coffee: With only about 3-5 calories per cup and no fat, protein, or sugar, plain black coffee is safe to drink. It can also help suppress your appetite. Avoid adding milk, cream, or sugar.
Unsweetened Tea: Black, green, and herbal teas (like chamomile or ginger) without added sweeteners are excellent calorie-free options. They offer antioxidants and can be soothing.
Sparkling Water: For those who miss the fizz of soda, unsweetened sparkling water is a great calorie-free alternative to satisfy cravings for carbonated drinks.
Zero-Calorie Sweeteners (with caution): While technically calorie-free, the use of sweeteners like stevia or monk fruit is debated. Some argue the sweet taste can still trigger an insulin response in certain individuals. For a strict fast, it's best to avoid them.

What to Eat During Your Eating Window

Once your fasting window is over, it's not a free-for-all to consume junk food. The success of intermittent fasting depends heavily on making healthy food choices during your eating window to ensure you get the nutrients you need. Focusing on whole, nutrient-dense foods helps maximize the metabolic benefits and promotes a feeling of fullness.

Here is a list of recommended foods:

Lean Proteins: Including skinless chicken, fish, eggs, and legumes will help you feel satiated for longer periods.
Healthy Fats: Incorporate sources like avocado, olive oil, nuts, and seeds into your meals. These are essential for overall health and help with nutrient absorption.
Vegetables: Load up on fibrous and nutrient-rich vegetables such as leafy greens, broccoli, cucumbers, and cauliflower.
Fruits: Enjoy whole fruits like berries, apples, bananas, and pears for natural energy, vitamins, and antioxidants.
Whole Grains: Complex carbohydrates like quinoa, oats, and buckwheat provide sustained energy during your eating period.
Bone Broth: Some individuals on a more flexible or 'dirty' fast might consume bone broth during the fasting window, but it's most effectively used to break a fast. It is rich in electrolytes and can ease your digestive system back into eating.

Comparison of Fasting-Friendly vs. Fast-Breaking Foods

To make it clearer what to consume, here is a comparison table outlining foods and drinks that are generally permitted versus those that should be avoided during the fasting period.


Allowed During Fast	Avoid During Fast
Plain Water, Sparkling Water	Juices, Sugary Sodas, Energy Drinks
Black Coffee (no milk/sugar)	Coffee with Milk, Cream, Butter (Bulletproof)
Unsweetened Herbal & Green Tea	Sweet Tea, Flavored Syrups
Minimal Electrolyte Powder in Water	Protein Powder, Collagen Supplements
A pinch of Pink Himalayan Salt	Honey, Agave, Maple Syrup
Bone Broth (small amount, dirty fast)	All solid food, Processed Snacks
Spices (cinnamon, nutmeg) in Coffee/Tea	Alcohol

How to Break Your Fast Effectively

When your eating window opens, it's best to introduce food slowly to avoid shocking your digestive system. Starting with a large, heavy meal can cause discomfort and bloating. A good strategy is to begin with easily digestible foods and gradually move to larger, more complex meals.

Here are some tips for breaking a fast:

Start Small: Begin with a small portion of a light, nutrient-rich food like a hard-boiled egg, a small bowl of soup, or a handful of nuts.
Prioritize Protein and Healthy Fats: A meal rich in lean protein and healthy fats, such as a salad with chicken or salmon and a drizzle of olive oil, can be a great first meal.
Stay Hydrated: Continue drinking water and other calorie-free liquids. Rehydrating is important, and it can also help you avoid overeating.
Avoid Sugar and Processed Foods: Breaking your fast with sugary or highly processed foods will cause a rapid spike in blood sugar and negate many of the benefits of fasting.

Conclusion

Intermittent fasting is more about when you eat than what you eat, but the quality of your food during the eating window is paramount to your success. To stay in a fasted state, only calorie-free liquids such as plain water, black coffee, and unsweetened teas are permitted. For your feeding window, focus on nourishing, whole foods rich in lean proteins, healthy fats, and complex carbohydrates to maximize the health benefits and support your weight management goals. By paying careful attention to both your fasting and eating periods, you can harness the full potential of this dietary approach.

Need help planning your IF meals?

To find out more about meal planning, consult the following resources:

Frequently Asked Questions

No. Adding cream, milk, or sugar to your coffee provides calories and will break your fast. You must stick to plain black coffee during the fasting window.

While zero-calorie drinks like diet soda won't provide calories, their effect on insulin response is debated. For the strictest fast, it's best to stick to water, black coffee, and unsweetened tea.

Start with small, easily digestible foods like bone broth, a handful of nuts, or a small portion of soup. Gradually introduce larger, more complex meals as your system readjusts.

Most experts advise against chewing gum or having mints, as the sweet taste can trigger an insulin response and potentially break your fast. It is best to avoid them to maintain a pure fasted state.

You should drink plenty of plain water throughout your fasting period to stay hydrated. A good rule of thumb is to drink a glass of water with every cup of black coffee or tea.

Many people find that drinking plain water, black coffee, or unsweetened tea helps curb hunger. It's also important to listen to your body and remember that initial hunger pangs will likely subside as you adjust.

Adding a small dusting of calorie-free spices like cinnamon or nutmeg to your black coffee or tea is generally acceptable and will not break your fast.