How Can I Fast Correctly? A Safe Guide for Beginners

November 20, 2025 •

4 min read

According to Johns Hopkins neuroscientist Mark Mattson, our bodies have evolved to function well for many hours without food, supporting the practice of fasting. Learning how to fast correctly is a skill that can provide numerous health benefits when approached with the right knowledge and precautions.

Quick Summary

This guide covers various correct fasting methods, pre-fast preparation, the importance of hydration and electrolytes, and how to safely reintroduce food for a successful fasting experience.

Key Points

Start Gradually: Begin with shorter fasting periods, like 12 hours (e.g., 12:12 method), and slowly increase the duration as your body adjusts.
Prioritize Hydration: Consistently drink plenty of water and, for longer fasts, consider adding electrolytes to prevent dehydration-related side effects.
Prepare and Break a Fast Properly: Eat smaller, whole-food meals before your fast and break it gently with light, easy-to-digest foods like soups and soft fruits.
Focus on Nutrition During Eating Windows: Emphasize balanced meals with complex carbohydrates, lean proteins, healthy fats, and plenty of vegetables and fruits.
Listen to Your Body: Pay close attention to how you feel; if you experience concerning symptoms like severe dizziness or nausea, stop the fast immediately.
Consult a Professional: Always seek medical advice before starting a new fasting regimen, especially if you have pre-existing health conditions or are on medication.

Before You Begin: Preparation is Key

For a successful and safe experience, proper preparation is essential, especially for beginners. A correct fasting routine should not be started impulsively, but rather with mindful planning to ease your body into the process.

Physical and Mental Preparation

Gradual Reduction: In the days leading up to your fast, gradually reduce your meal sizes. Avoid heavy, sugary, or fried foods, which can cause cravings and make the initial hours of fasting more difficult.
Hydration Pre-Loading: Increase your water intake in the 24 hours before you begin to help your body stay hydrated. Some experts also recommend focusing on water-rich foods like fresh fruits and vegetables.
Set Clear Intentions: Understand your purpose for fasting, whether it's for weight management, metabolic health, or spiritual reasons. This mental clarity can strengthen your resolve during challenging moments.
Timing is Everything: Choose a fasting schedule that fits your lifestyle. Weekends or less stressful days are often easier for beginners, allowing you to rest more if needed.

Popular and Correct Fasting Methods

There is no single "correct" way to fast, but several popular methods offer different entry points and intensities for beginners and experienced fasters. Intermittent fasting involves cycling between periods of eating and fasting.

Types of Intermittent Fasting

12:12 Method: This is the most beginner-friendly approach, involving a 12-hour eating window and a 12-hour fast. Since much of this is done while you sleep, it's an easy way to start.
16:8 Method: A widely practiced method that involves fasting for 16 hours and eating all your meals within an 8-hour window. For instance, you could eat between noon and 8 p.m., skipping breakfast.
5:2 Diet: This involves eating normally for five days of the week and restricting your calorie intake to about 500-600 calories on two non-consecutive days.
Weekly 24-Hour Fast: Known as "Eat-Stop-Eat," this involves a 24-hour fast once or twice a week. Many fast from dinner one day to dinner the next. It's more challenging and may be better for those with prior experience.

The Critical Role of Hydration

Many of the common side effects of fasting, such as headaches, fatigue, and dizziness, are due to dehydration and electrolyte imbalance. Staying properly hydrated is arguably the most important component of a safe fast.

Drink Plenty of Water: Aim for at least 2 liters of water daily, sipping consistently throughout your fasting window.
Replenish Electrolytes: Fasting can cause your body to lose essential minerals like sodium, potassium, and magnesium. On longer fasts (over 24 hours) or for those who exercise, a calorie-free electrolyte supplement or a pinch of salt in your water can be beneficial.
Acceptable Drinks: During a clean fast, only water, black coffee, and plain tea are recommended. Avoid anything with calories, sugar, or artificial sweeteners, as these can trigger an insulin response and break your fast.

Comparison: Foods to Ease Back In vs. Foods to Avoid


To Eat When Breaking a Fast	To Avoid When Breaking a Fast
Broth/Soups: Gentle on the stomach and rehydrating.	Heavy, Fried, or Fatty Foods: Can overwhelm your digestive system and cause bloating.
Cooked Vegetables: Steamed or boiled vegetables provide nutrients without excess fiber.	Simple Sugars/Sweets: Cause rapid blood sugar spikes and crashes.
Water-rich Fruits (e.g., Watermelon): Hydrating and easy to digest.	Raw, High-Fiber Veggies: Can be tough on a system that's been resting.
Small, Lean Proteins (e.g., eggs): Provides essential nutrients and keeps you full.	Large, Heavy Meals: Can lead to digestive distress and tiredness.

Listening to Your Body and When to Stop

While temporary hunger and mood changes are normal, certain signs indicate you should stop fasting immediately and seek medical attention if symptoms are severe. These include extreme weakness, prolonged nausea, or confusion. Always trust your body's signals.

Who Should Avoid Fasting?

Fasting is not suitable for everyone, and certain individuals should always consult a healthcare professional before starting. These groups include children and teens under 18, pregnant or breastfeeding women, people with a history of eating disorders, and those with underlying medical conditions like diabetes, kidney problems, or low blood pressure.

Conclusion: Making Fasting a Sustainable Practice

Learning how to fast correctly is a journey of understanding your body's signals and needs. By starting with shorter fasts, prioritizing hydration, and choosing nutritious, whole foods during your eating windows, you can harness the potential benefits of fasting safely. Remember that this should be a sustainable practice, not a short-term, punishing diet. A mindful and gradual approach is the most effective way to integrate fasting into a healthy lifestyle for the long term. For more in-depth information, resources from reputable institutions like Johns Hopkins Medicine are excellent references.

Johns Hopkins Medicine's intermittent fasting guide

Frequently Asked Questions

The easiest method for beginners is the 12:12 fast, which involves a 12-hour eating window and a 12-hour fasting window, as much of the fasting occurs during sleep.

During a 'clean' fast, you can have water, black coffee, and plain tea. Avoid any beverages with calories, sugar, or artificial sweeteners, as these can trigger an insulin response.

To manage hunger, try drinking more water or black coffee/tea. Distract yourself with work or hobbies, and remember that initial hunger pangs often subside as your body adjusts.

Break your fast with light, easy-to-digest foods like vegetable broth, cooked vegetables, or water-rich fruits such as watermelon. Gradually reintroduce more substantial foods.

Avoid heavy, fatty, or sugary foods immediately after a fast. Fried snacks and desserts can shock your system and lead to digestive discomfort.

Moderate, low-intensity exercise like walking or stretching is generally acceptable. Avoid strenuous physical activity, especially during extended fasts, and listen to your body.

Individuals who are pregnant, breastfeeding, under 18, or have a history of eating disorders or conditions like diabetes should not fast without consulting a medical professional.