Is it Safe to Fast 24 Hours Twice a Week?

January 8, 2026 •

4 min read

Research indicates that fasting for up to 24 hours, once or twice a week, may be safe and provide health benefits for many adults. This practice, also known as the Eat-Stop-Eat method, can lead to weight loss, improved metabolic health, and reduced inflammation. However, it is crucial to understand the risks and consult with a healthcare professional before beginning.

Quick Summary

This guide examines the safety and effectiveness of practicing a 24-hour fast twice weekly, a popular intermittent fasting schedule. It covers potential health benefits such as weight management and metabolic improvements, outlines the associated risks and common side effects, and provides guidance on who should avoid this fasting method, including preparation and safe refeeding strategies.

Key Points

Generally Safe for Healthy Adults: Fasting for 24 hours twice a week is typically safe for most healthy individuals, but medical consultation is advised.
Benefits Weight Loss and Metabolism: This intermittent fasting approach can help with weight management, improve blood sugar, and reduce insulin resistance.
Promotes Cellular Repair (Autophagy): Extended fasting periods trigger the process of autophagy, where the body cleanses damaged cells.
Potential Side Effects: Common side effects include hunger, fatigue, irritability, and headaches, especially during the initial adaptation period.
Hydration is Crucial: Drinking plenty of calorie-free fluids like water, black coffee, and tea is essential during the 24-hour fast.
Not for Everyone: Certain groups, such as pregnant or breastfeeding women, children, and individuals with a history of eating disorders or diabetes, should not fast.
Proper Refeeding is Important: Breaking the fast with a small, nutrient-dense meal helps prevent digestive issues.
Eat Nutritious Meals on Non-Fast Days: To prevent nutrient deficiencies, ensure your regular meals are well-balanced and rich in essential nutrients.

Understanding the 'Eat-Stop-Eat' Method

Fasting for 24 hours twice a week is a form of intermittent fasting popularized by the 'Eat-Stop-Eat' method. This approach involves abstaining from food for a full 24-hour period, for example, from dinner one day to dinner the next. During the fasting window, only zero-calorie beverages like water, black coffee, and herbal tea are permitted to maintain hydration. This strategy cycles between periods of normal eating and extended calorie restriction.

Potential Benefits of 24-Hour Fasting

For many healthy adults, this fasting protocol offers several notable health advantages:

Weight Management: By naturally restricting calorie intake over the course of the week, this method can lead to weight and fat loss. Some studies even suggest it can be more effective for weight loss than continuous calorie restriction.
Metabolic Health: Regular 24-hour fasts may improve metabolic markers such as blood sugar control, insulin sensitivity, and cholesterol levels. This improved metabolic function helps reduce the risk of conditions like type 2 diabetes and cardiovascular disease.
Autophagy: Extended fasting triggers autophagy, a process of cellular repair and rejuvenation. During autophagy, the body's cells clean out damaged components, which may contribute to anti-aging effects and a lower risk of age-related diseases.
Cardiovascular Health: Evidence suggests that consistent fasting can reduce risk factors for heart disease by lowering levels of triglycerides and harmful cholesterol. A 2018 study even found a reduction in the compound TMAO, which is linked to increased heart disease risk.

The Risks and Side Effects to Consider

While potentially beneficial, fasting for 24 hours twice a week is not without risks, especially for those with pre-existing conditions or who are new to fasting:

Potential for Nutrient Deficiencies: Failing to consume a nutrient-dense diet on non-fasting days could lead to vitamin and mineral deficiencies over time. It's crucial to replenish your body properly during eating periods to avoid malnutrition.
Hunger and Fatigue: Many people experience significant hunger pangs, fatigue, irritability, and headaches during the fasting window, particularly when first starting. These side effects tend to lessen as the body adapts over several weeks.
Risk of Overeating: Some individuals may compensate for the fasting days by overeating during their feeding windows, negating the calorie-reduction benefits and causing digestive discomfort.
Dehydration: It is critical to stay hydrated with water and other zero-calorie fluids while fasting. Inadequate fluid intake can lead to dehydration, dizziness, and electrolyte imbalances.

Comparison of Fasting Protocols


Feature	24-Hour Fast (Twice Weekly)	16:8 Method (Daily)	5:2 Method (Twice Weekly)
Fasting Window	Two full 24-hour periods per week	16 hours of fasting every day	Two non-consecutive days per week
Eating Window	Five days of normal eating	An 8-hour window every day	Five days of normal eating, 500-600 calories on fast days
Intensity	High intensity; can be challenging initially	Moderate intensity; easier for most to adapt to daily	Moderate intensity; structured calorie restriction
Metabolic Shift	Promotes pronounced metabolic switching to fat-burning mode due to longer fasts.	Consistent, but less dramatic metabolic switching each day.	Calorie restriction on two days promotes a metabolic shift.
Side Effects	More pronounced initial hunger, irritability, and fatigue.	Generally milder side effects as adaptation occurs.	Can cause hunger and fatigue on restricted days.
Key Benefit	Stronger activation of autophagy and potential for more significant fat loss.	Consistency and sustainability for long-term adherence.	Flexibility and less restrictive for daily meals.

Who Should Avoid This Fasting Approach

Certain individuals should not attempt 24-hour fasting twice a week without strict medical supervision:

Individuals with a history of eating disorders.
Those who are pregnant or breastfeeding.
People with type 1 or uncontrolled type 2 diabetes.
Children and adolescents under 18.
Individuals recovering from surgery or with compromised immune systems.
Anyone taking medications that require food for proper absorption.

Safely Incorporating the Fast

If you are a healthy adult and wish to try this method, a few steps can increase its safety and effectiveness:

Start Slowly: Begin with shorter fasting periods, such as a 16:8 schedule, to allow your body to adapt before attempting a full 24-hour fast.
Hydrate: Drink plenty of water throughout the fasting period to combat hunger, fatigue, and dehydration.
Eat Nutrient-Dense Meals: On non-fasting days, prioritize healthy, balanced meals rich in protein, fiber, and essential nutrients to support your body.
Break the Fast Gently: When ending your fast, start with a small, easily digestible meal like a soup or smoothie. This prevents overwhelming your digestive system with a large meal.
Listen to Your Body: Pay close attention to how you feel. If you experience persistent discomfort, severe dizziness, or other concerning symptoms, stop the fast and consult a doctor.

Conclusion: A Powerful Tool, Not a Panacea

For many healthy individuals, practicing a 24-hour fast twice a week can be a safe and powerful tool for weight management, metabolic improvement, and promoting cellular repair. However, it is a high-intensity intermittent fasting protocol that requires careful planning, proper nutrition on eating days, and attentive listening to your body's signals. The initial side effects of hunger and irritability are common but often subside as your body adapts. Critically, it is not suitable for everyone, and certain populations must avoid it entirely due to potential health risks. As with any significant dietary change, discussing your plans with a healthcare professional is the most responsible first step to ensure your safety and success. For those who can adhere to it safely, this method can unlock significant health benefits by leveraging the body's natural fasting mechanisms.

InsideTracker Article on 24 Hour Fast

Frequently Asked Questions

This method is often referred to as the 'Eat-Stop-Eat' approach, a type of intermittent fasting where you fast completely for two non-consecutive 24-hour periods each week.

After about 8 to 12 hours without food, your body depletes its glycogen stores and switches to burning stored fat for energy. This metabolic shift, known as ketosis, is what drives many of the benefits of fasting.

Yes, by restricting your weekly calorie intake, a 24-hour fast twice a week can be an effective strategy for weight loss. Studies show it can be as effective as daily calorie restriction for shedding pounds.

A well-managed 24-hour fast twice a week is unlikely to cause significant muscle loss, especially when combined with a proper resistance training routine and sufficient protein intake on non-fasting days. The body tends to burn stored fat rather than muscle for a 24-hour period.

To safely break your fast and avoid digestive upset, start with a small, easy-to-digest meal. Foods like soup, smoothies, or a handful of nuts are good options before gradually reintroducing larger meals.

During your fast, you should stick to zero-calorie beverages to maintain hydration. Good options include water, black coffee, unsweetened tea, and herbal tea.

It is highly recommended to consult a doctor before starting if you have any pre-existing conditions, especially diabetes, a history of eating disorders, or if you are pregnant, breastfeeding, or under 18.