How to do a 36 hour fast once a week for maximum metabolic benefits

October 15, 2025 •

4 min read

Research indicates that longer fasts, such as a 36-hour regimen, can promote a more significant increase in autophagy—the body’s process for cellular repair and renewal—than shorter fasting windows. For those with experience, learning how to do a 36 hour fast once a week is an advanced step toward reaping these profound metabolic rewards.

Quick Summary

A detailed blueprint for safely completing a 36-hour fast every week, including the preparatory steps and the best methods for refeeding. Discusses common side effects and highlights key benefits like enhanced fat burning and cellular repair.

Key Points

Preparation is Crucial: Start with shorter fasting windows (e.g., 16:8) before attempting a 36-hour fast to allow your body to adapt.
Hydration is Non-Negotiable: Drink plenty of water, black coffee, or herbal tea throughout the fast to manage hunger and prevent dehydration.
Maximize Fat-Burning: A 36-hour fast pushes your body into a deeper state of ketosis, promoting more efficient fat utilization for energy.
Plan Your Break Carefully: Reintroduce food with small, easily digestible meals like bone broth or steamed vegetables to avoid digestive discomfort.
Monitor Your Body's Signals: Pay attention to side effects like headaches or dizziness and stop the fast safely if you experience severe discomfort.
Enhance Cellular Repair: The longer duration is linked to a more significant boost in autophagy, the body's cellular cleansing process.
Schedule Strategically: Choose a less demanding day of the week for your fast to minimize physical and mental stress.

Understanding the 36-Hour Fast

The 36-hour fast, sometimes referred to as the 'Monk Fast,' is a form of intermittent fasting that involves abstaining from all caloric intake for 36 consecutive hours. This typically means finishing dinner on one evening and not eating again until breakfast on the day after next. For example, if you eat dinner at 7 PM on Monday, your next meal would be breakfast at 7 AM on Wednesday, completing a full 36 hours. During this time, only non-caloric beverages like water, black coffee, and herbal teas are permitted. This fasting duration is believed to push the body beyond its glycogen reserves, forcing it to utilize stored fat for energy, a metabolic state known as ketosis.

Potential Benefits of a Weekly 36-Hour Fast

Incorporating a 36-hour fast once a week can offer several potential health advantages for experienced fasters. These benefits include:

Enhanced Autophagy: A key cellular process where the body cleans out damaged cells and regenerates new ones. Autophagy is believed to increase significantly after the 24-hour mark.
Improved Insulin Sensitivity: By reducing blood sugar and insulin levels for an extended period, the body becomes more efficient at regulating glucose.
Significant Weight and Fat Loss: As the body enters ketosis, it begins burning stored fat for fuel. A weekly 36-hour cycle can create a significant calorie deficit over time.
Reduced Inflammation: Fasting has been shown to lower inflammatory markers in the body, which can help mitigate the risk of chronic diseases.
Better Heart Health: Regular fasting may improve cardiovascular markers such as blood pressure and cholesterol levels.
Mental Clarity and Focus: Many individuals report feeling more mentally sharp during the later stages of a fast due to increased production of brain-derived neurotrophic factor (BDNF).

Step-by-Step Guide to a Successful Weekly 36-Hour Fast

To maximize the benefits and minimize discomfort, careful planning is essential. For beginners, it is highly recommended to build up to this duration from shorter fasting windows, such as 16:8 or 24 hours.

Preparation Phase (Pre-Fast)

Choose the Right Day: Select a day with minimal physical and social demands. A weekend or a day off from work is often ideal to allow for rest.
The Last Meal: Your last meal before the fast should be rich in healthy fats, protein, and fiber, and low in simple carbohydrates. This helps stabilize blood sugar and keeps you feeling full longer. Examples include salmon with avocado and steamed vegetables, or a salad with grilled chicken and olive oil.
Hydrate Well: Increase your fluid intake in the 24 hours leading up to your fast to start in a well-hydrated state. You can also mix a pinch of salt into your water for added electrolytes.

The Fasting Period (The 36 Hours)

Stay Hydrated: This is the most crucial aspect. Sip plenty of water throughout the 36 hours. You can also have black coffee and herbal teas without milk or sugar. Some also find bone broth helpful for replenishing electrolytes, though it technically contains a small number of calories.
Manage Your Day: Schedule distracting, low-intensity activities to keep your mind off food. Light walking or yoga is acceptable, but avoid strenuous exercise that could lead to dehydration and fatigue.
Recognize Side Effects: Expect some hunger pangs, headaches, or irritability, especially during your first few attempts. These symptoms typically subside as your body adapts. However, if you experience severe discomfort or signs of extreme dehydration like dizziness, it is important to break your fast safely.

Breaking the Fast (The Refeeding)

Start Gently: Your digestive system has been dormant and needs a gentle reintroduction to food. Begin with a small, easily digestible meal. Overeating or consuming heavy, fatty foods immediately can lead to digestive distress.
Smart Food Choices: Opt for a nourishing bone broth, a handful of nuts, or a small portion of steamed vegetables. Fermented foods like yogurt can also help reintroduce healthy gut bacteria.
Build Up Gradually: After the initial gentle meal, you can have a more substantial, balanced meal containing lean protein, healthy fats, and low-glycemic carbs.

Comparison: 36-Hour Fast vs. Shorter Fasts


Feature	16:8 Fast (Daily)	24-Hour Fast (Weekly)	36-Hour Fast (Weekly)
Frequency	Daily eating window	Once a week	Once a week
Duration	16 hours fasting, 8 hours eating	24 hours fasting	36 hours fasting
Ketosis	May induce mild ketosis late in the fasting window	Often induces ketosis	Deepens ketosis, more time in fat-burning state
Autophagy	Minor increase, primarily cell maintenance	Initial boost, more effective than 16:8	Significantly enhanced autophagy
Difficulty	Easiest for beginners	Intermediate, requires planning	Advanced, more challenging but rewarding
Flexibility	Highly flexible, easy to incorporate daily	Requires planning around one day	More restrictive, requires planning for two consecutive evenings/mornings

Final Conclusion

Implementing a weekly 36-hour fast can be a powerful tool for weight management and overall metabolic health, particularly for experienced individuals. The practice promotes enhanced fat burning through ketosis and triggers significant cellular repair via autophagy. Success, however, relies heavily on proper preparation, staying adequately hydrated with non-caloric fluids, and carefully managing the refeeding process with easily digestible, nutrient-dense foods. Listening to your body is paramount, and easing into the schedule is crucial for sustainability. As with any significant dietary change, it is strongly recommended to consult a healthcare professional before starting, especially if you have pre-existing health conditions, to ensure it is the right and safe option for you. Johns Hopkins Medicine offers additional resources on intermittent fasting basics.

Frequently Asked Questions

No, a 36-hour fast is generally not recommended for beginners. It is best to start with shorter, less demanding intermittent fasting methods, such as the 16:8 method, and gradually increase the fasting duration as your body adapts.

During the fasting period, you can drink water, black coffee, and plain herbal tea. It is important to avoid all caloric beverages and any additions like milk, sugar, or artificial sweeteners.

Common side effects include hunger pangs, headaches, fatigue, and irritability, especially in the early stages. Staying well-hydrated can help mitigate some of these symptoms. Most side effects lessen as your body becomes accustomed to the fasting routine.

To prevent digestive shock, your first meal should be small and easily digestible. Ideal choices include bone broth, steamed vegetables, a small serving of lean protein like eggs, or a handful of nuts.

A once-a-week schedule is a sustainable and popular approach for many healthy individuals. For some, fasting more frequently might be possible, but it should only be done under the supervision of a healthcare professional.

Light-to-moderate exercise, such as walking or yoga, is usually acceptable. However, it's best to avoid intense workouts due to the increased risk of dehydration and fatigue when not consuming calories.

A 36-hour fast generally results in a larger calorie deficit over time, and the extended period in ketosis can lead to more significant fat burning and weight loss compared to a 24-hour fast.