Types of Fasting: How Different Approaches Work and How to Choose One

Fasting, the practice of abstaining from food and sometimes drink for a set period, has been a part of human culture for thousands of years for spiritual, cultural, and health reasons. Today, many people explore fasting for its potential benefits, including potential effects on metabolic markers and weight management for some people. However, with numerous approaches available, understanding the different types of fasting methods is key to finding one that aligns with your goals, lifestyle, and overall wellbeing.

This guide summarizes common methods and what current research explores about the most common fasting protocols. We will explore the various methods, considerations, and provide a framework to help you determine which approach, if any, is right for you. Think of this as your starting point for making an informed decision about integrating fasting into your wellness routine.

Every fast is a personal experience. Your dietary preferences, body composition, and activity level all influence your fasting journey. It’s advisable to consult with a healthcare provider before embarking on a fasting regimen.

Is Fasting Suitable for Everyone?

While for some adults, certain fasting methods may be an option, it is not suitable for everyone. The body’s response to fasting can vary significantly based on individual health status, medical history, and lifestyle. It is always recommended to consult with a healthcare professional, such as a doctor and/or dietitian, before starting any new fasting regimen, especially if you have pre-existing health conditions (1).

Certain individuals should approach fasting with extreme caution and under strict medical supervision, while others should avoid it altogether.

Individuals who should generally avoid fasting include (1):

• Pregnant or breastfeeding women: Nutritional needs are significantly increased during these periods to support both the mother and the developing baby. Restricting calories or nutrients can pose serious risks (2).
• Individuals with a history of eating disorders: Fasting can trigger or exacerbate disordered eating patterns, such as anorexia nervosa or bulimia nervosa. The focus on food restriction can be psychologically harmful (3).
• Children and adolescents: Growing bodies require a consistent and adequate supply of energy and nutrients for proper development. Fasting can interfere with this critical process (4, 5).
• Individuals who are underweight (BMI < 18.5): Further calorie restriction can lead to nutritional deficiencies and other serious health complications.

Individuals who should seek medical supervision before fasting include:

• People with Type 1 or Type 2 diabetes: Fasting can cause dangerous fluctuations in blood sugar levels (hypoglycemia or hyperglycemia) if not properly done (6). Adjustments to medication, such as insulin, are often necessary and must be managed by a doctor.
• Those taking prescription medications: Fasting can affect how some drugs are absorbed and metabolized (7). Medications that need to be taken with food may require a revised schedule.
• People with kidney or liver conditions: These organs are crucial for processing waste products and metabolizing nutrients (8, 9). Fasting can place additional stress on them (10, 11).
• Individuals with heart conditions or low blood pressure: Electrolyte shifts during fasting can potentially affect heart rhythm and blood pressure (12, 13).
• Older adults: They may be more susceptible to muscle loss, dehydration, and nutrient deficiencies (14), making supervised fasting essential.

Read more: Fasting Diets for Seniors: The Best Intermittent Fasting Diets for over-65-Year-Olds

What Are the Five Types of Fasting?

The world of fasting can seem complex, but most protocols can be grouped into five main categories. Understanding each different type of fasting will help you identify which one might best suit your objectives.

1. Intermittent Fasting (IF)

Intermittent fasting is arguably the most popular approach. It focuses on when you eat rather than what you eat, by cycling between periods of eating and voluntary fasting. This structure makes it one of the more flexible types of fasting methods. The core principle is to create a consistent daily or weekly pattern (15).

• Time-Restricted Eating (TRE): This involves eating all your meals within a specific window each day and fasting for the remaining hours (16). The most common protocol is the 16:8 method, where you fast for 16 hours and eat during an 8-hour window (e.g., 12 PM to 8 PM). Other variations include 14:10, 18:6, and 20:4 (also known as the Warrior Diet).
• The 5:2 Diet: This involves eating normally for five days of the week and restricting calorie intake to approximately 500-600 calories on two non-consecutive days (15).
• Eat-Stop-Eat: This method involves a full 24-hour fast once or twice a week (17). For example, you might finish dinner at 7 PM on Monday and not eat again until 7 PM on Tuesday.
• Alternate-Day Fasting: As the name suggests, this involves alternating between days of normal eating and days of complete fasting or very low-calorie intake (18).

2. Prolonged Fasting

Prolonged fasting, sometimes called extended fasting, involves abstaining from food for periods longer than 24 hours. These fasts typically last anywhere from 36 hours to several days (19) and are often undertaken for more significant potential physiological effects, such as cellular recycling processes (autophagy) or temporary metabolic changes during fasting (20).

A common form is water fasting, where only water is consumed for the duration of the fast (typically 24 to 72 hours). Due to the increased risk of dehydration, electrolyte imbalance, and other complications (21), prolonged fasting should only be attempted by experienced individuals, preferably under the guidance of a healthcare professional.

3. Dry Fasting

Dry fasting is the most extreme form of fasting, as it involves abstaining from both food and water. This practice is associated with significant risks, including hypoglycemia, kidney strain, and electrolyte imbalances (22).

• Soft Dry Fasting: Allows for external contact with water, such as showering.
• Absolute (or Hard) Dry Fasting: Prohibits any contact with water.

Given the critical role of hydration in bodily functions, this method is not recommended for most people and carries a high risk of adverse health events. If you are interested in learning about the perceived benefits and significant risks associated with this practice, you can find more information about dry fasting, but we also suggest talking to your healthcare provider.

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4. Partial Fasting

Partial fasting involves restricting certain types of foods or drinks for a defined period rather than complete food abstinence. This approach is often seen as more manageable than a full fast, as it still allows for some energy intake.

• Juice Fasting: Also known as a “juice cleanse,” this involves consuming only fruit and vegetable juices for a set period. While it provides vitamins and minerals, it typically lacks fiber, protein, and fat (23).
• Daniel Fast: This is a plant-based fast inspired by the biblical figure Daniel. It typically involves consuming only fruits, vegetables, whole grains, legumes, nuts, and seeds while avoiding all animal products, dairy, processed foods, and stimulants like caffeine (24).
• Fat Fasting: This approach involves consuming the majority of calories (80-90%) from fat, with very low protein and carbohydrate intake, for a short period (2-5 days) to induce ketosis (25).

5. Religious and Spiritual Fasting

For millennia, fasting has been a central practice in many of the world’s religions and spiritual traditions. The motivation behind this type of fasting is typically for spiritual purification, devotion, or commemoration rather than physical health benefits (26).

• Ramadan Fasting: Muslims abstain from all food and drink from dawn until sunset for an entire month.
• Yom Kippur Fasting: In Judaism, this involves a 25-hour fast with no food or water as a day of atonement.
• Lent Fasting: In some Christian denominations, this involves abstaining from certain foods, like meat, on specific days during the 40-day period leading up to Easter.

Which Type of Fasting is Best for Beginners?

For those new to fasting, Intermittent Fasting (IF) is widely considered the best starting point. Its structured yet flexible nature makes it easier to adopt and sustain compared to more restrictive methods. Here’s why IF is an ideal entry into the world of fasting.

Its Flexibility is Unmatched

Unlike prolonged or dry fasts, IF offers various schedules. You can choose a protocol that fits your lifestyle, social commitments, and daily routine. 

The 16:8 method, for example, often just means skipping breakfast and having a later lunch, which many people find manageable. This adaptability makes it less intimidating and increases the likelihood of long-term adherence (27). 

Finding the best intermittent fasting schedule for you is a matter of personal preference and daily rhythm.

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It’s Easier to Adopt

The transition into IF is generally smoother than with other fasting types. 

You can start by gradually extending your fasting window—perhaps beginning with a 12:12 schedule (12 hours of fasting, 12 hours of eating) and slowly working your way up to 14:10 or 16:8. 

This progressive approach allows your body to adjust to the new eating pattern without the shock of a multi-day fast. The psychological barrier is also lower, as you know you will be eating every single day.

Research Has Explored Potential Benefits

Intermittent fasting is not just popular; it’s also widely studied compared to other fasting approaches. Research suggests that IF might offer numerous health benefits, including:

• improved insulin sensitivity (28),
• support for weight management (29), and
• Possible enhanced cellular repair processes (30).

These tangible benefits can be motivating for beginners, providing positive reinforcement to stick with the practice.

The specific advantages can even be tailored based on a person’s life stage, leading many to explore intermittent fasting by age.

Read more: BetterMe Intermittent Fasting Overview (2026)

How to Choose the Best Type of Fasting for Yourself?

Selecting the best type of fasting is a personal decision that depends on a combination of factors. There is no single “best” method for everyone. Here are eight considerations to help guide your choice.

1. Your Health Goals: Are you aiming for weight loss, improved metabolic health, mental clarity, or longevity? Different fasting protocols may be better suited for different objectives. For instance, time-restricted eating is often used for weight management, while longer fasts are sometimes explored for possible benefits like autophagy.
2. Your Lifestyle and Schedule: A successful fasting plan is one you can stick to. Consider your work hours, family commitments, and social life. If you have frequent business dinners, a 24-hour fast might be difficult to maintain. A daily time-restricted eating window might be more practical.
3. Your Experience with Fasting: If you are a complete beginner, jumping into a 72-hour water fast is not advisable. Starting with a less intense method, like the 16:8 schedule, allows you to gauge your body’s response and build confidence.
4. Your Current Health Status: As discussed, your medical history is paramount. If you have any underlying health conditions or take medication, consulting a healthcare provider is non-negotiable. They can help you determine if fasting is safe and which approach may be most appropriate.
5. Your Psychological Relationship with Food: Be honest with yourself about your eating habits and mindset. If you have a tendency toward restrictive behaviors, a highly structured fasting plan may not be healthy for you. An approach that feels less about deprivation and more about mindful eating might be better.
6. Your Body’s Signals: Pay attention to how you feel. While some initial hunger and fatigue are normal, persistent dizziness, extreme weakness, or other concerning symptoms are signs that your current approach may be too aggressive. True wellness is about listening to your body, not punishing it.
7. Nutritional Needs: Ensure your eating window is long enough to consume all the necessary nutrients your body needs to thrive. A very narrow eating window could make it challenging to get adequate protein, fiber, vitamins, and minerals, especially for active individuals.
8. Flexibility for Social Situations: A rigid fasting plan can sometimes lead to social isolation. Choose a method that allows for some flexibility. For example, on the 5:2 diet, you can schedule your low-calorie days to avoid social events centered around food.

A more specialized approach, known as the fasting mimicking diet, offers a structured, low-calorie plan that aims to provide the benefits of fasting without complete food abstinence.

Which Form of Fasting Is Lower-Risk?

How fasting affects someone depends less on the exact method and more on the overall approach. Any fasting routine can involve risks if it isn’t planned thoughtfully, and longer or more intensive fasts usually require additional caution and guidance.

With that said, intermittent fasting – especially time-restricted eating patterns like the 16:8 schedule – is often viewed as one of the more approachable, lower-intensity options for many adults. The reasons are clear: it does not involve long periods without food, the risk of nutrient deficiency is low (assuming a balanced diet during the eating window), and the body is not placed under extreme stress. It maintains a daily rhythm of eating, which helps regulate hunger cues and energy levels more predictably than multi-day fasts.

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A safe approach to any type of fasting includes:

• Staying Hydrated: Unless you are undertaking a medically supervised dry fast, drinking plenty of water is crucial.
• Maintaining Electrolyte Balance: On longer fasts, sodium, potassium, and magnesium levels can drop. Some people choose electrolytes during longer fasts; discuss what’s appropriate for you with a clinician.
• Eating Nutritious Food: When you break your fast, focus on whole, nutrient-dense foods to replenish your body.
• Listening to Your Body: Do not push through severe dizziness, headaches, or nausea. These are signs to stop and re-evaluate.
• Starting Slow: Gradually increase your fasting duration to allow your body time to adapt.

Can a 3-Day Fast Be Harmful?

A 3-day (or 72-hour) water fast can be a powerful tool, but it also carries potential risks and should not be taken lightly. Whether it is harmful depends heavily on an individual’s health status and how the fast is conducted.

For a well-nourished individual, a 3-day fast can be a more intensive approach and should be treated cautiously. It may lead to several temporary side effects as the body adapts. These can include:

• Dehydration and Electrolyte Imbalance: Without careful management, fluid and mineral losses can lead to dizziness, muscle cramps, and headaches (1, 31).
• Hunger and Fatigue: The first 48 hours are often the most challenging, as the body burns through its glycogen stores and transitions to using fat for fuel (ketosis).
• Re-feeding Syndrome: This is a rare but serious risk associated with breaking a longer fast. Introducing food too quickly can cause dangerous shifts in fluid and electrolytes. This is a greater concern for malnourished individuals (32).
• Muscle Loss: While the body prioritizes fat for fuel, some muscle breakdown can occur at the beginning of a fast (33), especially if the fast is not supported by proper hydration and a gradual return to eating.

Despite these risks, a well-managed 3-day fast may also offer benefits, such as has been associated with changes in insulin sensitivity markers and inflammatory markers in some research, though findings are mixed, although more research needs to be done to understand the full picture (34). The key is preparation, proper hydration with electrolytes, and a careful re-feeding plan.

Frequently Asked Questions

• Does fasting help with weight loss?

Fasting may support weight loss for some people mainly by changing eating patterns and total intake; outcomes vary. Some studies also suggest fasting may boost metabolism slightly and improve hormone function to facilitate weight loss, such as by lowering insulin levels (35, 36).

• Can fasting improve metabolism?

Short-term fasting has been linked to temporary changes in stress hormones (including norepinephrine) in some studies (37). 

However, very long fasts (over 3 days) can have the opposite effect and slow down your metabolism. Theoretically, over time while practicing long fasts, the body adapts to conserve energy, entering a more energy-efficient state (38).

• What breaks a fast?

Strictly speaking, any food or drink containing calories will break a fast. This includes anything with carbohydrates, protein, or fat. The amount of calories needed to break a fast is debated, but most experts agree that anything over 5-10 calories will likely interrupt the fasting state.

• Can you drink water or coffee while fasting?

Yes, water is essential and should be consumed freely during most fasts. Many people stick to water, plain tea, or black coffee during fasting windows; individual tolerance varies. However, adding sugar, milk, or cream will break your fast.

• How often should you fast?

The frequency depends on the type of fasting. Time-restricted eating can be done daily. A 24-hour fast may be done once or twice a week. Longer fasts (48+ hours) should be done much less frequently, perhaps once a month or a few times a year, and ideally with medical guidance.

The Bottom Line

Choosing a type of fasting is a journey of self-experimentation and listening to your body. There is no magic formula, only the method that works sustainably for you. By starting slow, prioritizing safety, and aligning your approach with your unique goals and lifestyle, you can explore the potential benefits of this ancient practice in a modern, informed way.