At a glance
Fasting means avoiding calories for a set period of time, but there are several different types of fasting, including time-restricted eating, OMAD, alternate-day fasting, 5:2 fasting, 24-hour fasting, and extended fasting. These fasting methods may support weight loss, blood sugar balance, metabolic health, and digestive health when paired with a healthy diet, adequate protein, and proper hydration.
There are many types of fasting patterns, and choosing the right approach depends on personal factors such as lifestyle, underlying health conditions, and nutritional and fitness goals.
Learn about some of the most common fasting methods and how to choose the best fasting routine for your health goals.
What is fasting?
Fasting is a period during which you avoid eating calorie-containing foods and drinks for an extended period, allowing the body to shift from using incoming fuel to drawing more on stored energy.
There are several reasons to practice fasting, and it’s been used for religious, spiritual, and practical purposes for centuries. Today, it’s a major focus in health and wellness, widely practiced and studied for its effects on metabolic health and even chronic diseases.
“Fasting gives the body a break from constant eating, allowing insulin—the metabolic hormone that regulates blood sugar levels and fat storage—to decrease and the digestive system to rest,” explains Dr. Berg, “This allows processes such as autophagy and ketosis to occur much more efficiently, promoting cellular repair and deep fat-burning.”
Research published in EClinicalMedicine highlights that certain intermittent fasting (IF) techniques can offer significant health benefits, particularly for overweight or obese adults. Compared to a non-intervention diet, IF was associated with improved metabolic health markers, including waist circumference, fat mass, fasting insulin, and cholesterol.
Furthermore, instead of causing muscle wasting, the researchers also observed an increase in fat-free mass (FFM), meaning it helped participants retain or gain lean muscle while losing fat, effectively supporting overall body composition.
Watch the video below to discover some of the worst fasting methods.
So what does fasting actually look like?
The different types of fasting are generally categorized by how long each fast lasts and how often it repeats. Most methods fall into two broad categories: intermittent fasting and extended fasting.
Intermittent fasting (IF) includes several fasting patterns that typically involve fasting periods of less than 48 hours, practiced on a regular schedule. Extended fasting refers to longer fasts and is typically practiced less frequently.
Here are six common fasting methods.
1. Time-restricted eating
Time-restricted eating (TRE) is a widely practiced form of intermittent fasting. It involves regular periods of eating and fasting within a single day.
One of the most popular TRE patterns is the 16:8 method, which pairs roughly 16 hours of fasting with an eight-hour window for meals.
Other common TRE fasting windows include:
- 12:12—12 hours fasting with a 12-hour eating window.
- 14:10—14 hours fasting with a 10-hour eating window.
- 18:6—18 hours fasting with a 6-hour eating window.
- 20:4—20 hours fasting with a 4-hour eating window.
People often choose TRE because it is straightforward, fits easily into a daily routine, and oftentimes, a significant portion of fasting occurs overnight while you sleep.
According to research published in Obesity, TRE had the highest average participant retention rate (94 percent) among tested fasting methods, outperforming the 5:2 diet (88 percent) and alternate-day fasting (85 percent).
2. One meal a day
Experienced fasters sometimes work up to one meal a day (OMAD). This pattern of fasting involves eating one full meal within a short time frame, usually within a 1-hour window, and fasting the rest of the day.
OMAD can be a beneficial strategy for those seeking to spend more time in autophagy, although it can make achieving nutritional goals significantly more challenging, which is why it’s recommended to develop a personalized execution plan with a healthcare provider or a registered dietitian before attempting more restrictive patterns.
3. 24-hour fasting
The 24-hour fast, sometimes called eat-stop-eat, involves a full 24-hour fast that spans from one meal to the same meal the next day, such as from dinner to dinner.
Though this may sound similar to OMAD, it’s a slightly different technique as you stop eating for a full 24 hours. In contrast, with OMAD the fast is technically about 23 hours long. Importantly, a 24-hour fasting approach is typically only practiced 1 or 2 times a week, rather than daily like OMAD.
4. Alternate-day fasting
Alternate-day fasting (ADF) involves switching between eating days and fasting days. Some versions involve no calories on fasting days, while modified versions allow a small amount of food, often around 20 to 30 percent of typical intake.
People practice ADF for varying durations, anywhere from a few weeks to months at a time, depending on health goals.
5. 5:2 fasting
The 5:2 method involves eating normally for five days a week and restricting calories on the other two. On fasting days, women typically consume about 500 calories and men about 600 calories at any time of day. Because there are still calories being consumed, people may not reach the fasting state at all using this method if they spread the calories throughout the day, making it ineffective unless combined with TRE.
Fasting days usually aren’t consecutive. You can choose any days that fit your schedule, but it’s generally recommended to have at least one day of regular eating between fasts rather than two fasting days back-to-back.
6. Extended fasting
Extended fasting, also sometimes called prolonged fasting, involves abstaining from food for 48 hours or more.
Rather than a regular daily or weekly routine, this practice is typically performed every few months or years to help trigger a metabolic reset, support gut health, and maximize the potential benefits of autophagy. Autophagy is the body’s natural system for cleaning out, recycling, and repairing old, damaged cell structures.
Because extended fasting is more demanding on the body, it carries a higher risk of side effects and generally calls for medical supervision, especially for anyone with underlying health conditions.
How to choose the best fasting method
For beginners, time-restricted eating is usually the most practical starting point.
People who do well with structure may prefer the 16:8 or 18:6 intermittent fasting schedules. Those who frequently snack or feel tired or irritable while fasting may do better by starting with a wider eating window, such as 14:10, while prioritizing protein, electrolytes, sleep, and food quality.
ADF, 24-hour fasting, and 5:2 fasting can be good options for people who want to experiment with fasting without committing to a daily routine.
However, because variations of ADF and 5:2 allow for a small amount of calories during fasting days, they may not effectively achieve many of fasting’s core benefits, such as autophagy, unless combined with a TRE approach. Even a 500-calorie deficit can halt autophagy if it’s spread across frequent snacks, since eating triggers insulin and shuts down cellular cleanup.
Therefore, when following an ADF or 5:2 fasting plan, it’s recommended to avoid grazing on fasting days and consume your allotted calories in a single meal to maintain a more efficient fasting window.
Extended fasts are best reserved for experienced fasters who have safely adapted to shorter protocols. Typically lasting 48 to 72 hours or more, these advanced methods require careful planning, strategic electrolyte replenishment, and a structured refeeding phase to avoid digestive distress.
Because prolonged nutrient deprivation can lead to muscle loss, nutrient deficiencies, or refeeding syndrome, extended fasts should always be conducted under professional supervision to ensure safety and efficacy.
Safe fasting tips
The safest way to fast is to start gradually, stay hydrated, and ensure that eating windows provide adequate amounts of high-quality whole foods to support muscle mass, energy, and overall health.
Beginners should ease into fasting
Most practitioners recommend that beginners ease into fasting, starting with shorter fasting windows and gradually increasing as the body adapts.
In addition, consciously eating fewer meals by reducing snacking and aiming to reach nutrition goals at breakfast, lunch, or dinner can be a helpful way to more comfortably adapt to the lifestyle while supporting more stable insulin throughout the day.
Stay hydrated
Staying properly hydrated is essential during any fasting period. As stored glucose is depleted early in a fast, the body excretes significant amounts of water, and with it go key minerals like sodium, magnesium, and potassium.
Consuming mineral water or a high-quality, zero-calorie electrolyte beverage can help you stay adequately hydrated throughout your fast. During eating windows, a homemade electrolyte smoothie can also be a great way to naturally replenish depleted minerals.
Eat high-quality whole foods
Finally, what you eat when breaking a fast can significantly influence both how you feel during fasting and how well your body maintains its benefits over time.
Building meals around high-quality proteins may help prevent compensatory overeating and protect muscle mass.
Including healthy fats, non-starchy vegetables, and low-glycemic fruit can further support steady energy levels, promote healthy digestion, and provide antioxidants that support cellular resilience.
Who should be careful with fasting?
If you struggle with constant hunger, binge eating, poor mental health, or persistent low energy while adapting to fasting, your approach may be too aggressive. It can also signal a need to adjust other lifestyle factors, such as diet quality, hydration habits, or physical activity levels.
Additionally, people taking medications or living with certain health conditions should consult a healthcare provider for the right guidance before fasting. This may include individuals with:
- Gout
- Diabetes
- Low blood pressure
- Poor heart health
- Kidney disease
- Liver disease
- A history of fainting
- A history of disordered eating patterns or those who are underweight.
Breastfeeding women should also be cautious for medical reasons, as fasting and skipping meals regularly can affect energy levels, hydration, and milk supply.
Key takeaways
- Common fasting methods include time-restricted eating, OMAD, 24-hour fasting, alternate-day fasting, 5:2 fasting, and extended fasting.
- Time-restricted eating is usually the most practical starting point for beginners.
- Fasting may support weight loss, blood sugar balance, autophagy, and overall metabolic health.
- Safe fasting depends on gradual adaptation, adequate protein, hydration, and high-quality whole foods.
- People who use medications or have medical conditions should fast only with professional guidance.
FAQ
- 1. What is the easiest type of fasting to start with?
- 2. Can I drink water while fasting?
- 3. Is alternate-day fasting safe?
- 4. Is fasting the same as calorie restriction?