A 36-hour fast usually means going one full day plus two nights without calories. For example, you might finish dinner at 7 p.m. on Monday and eat again at 7 a.m. on Wednesday. It is much more restrictive than common daily intermittent fasting schedules such as 14:10 or 16:8.
Some people are interested in a 36-hour fast for appetite reset, weight-loss structure, or metabolic health. The safer way to think about it is more modest: a 36-hour fast is an advanced fasting pattern that may not be appropriate for many people. Longer fasts are not automatically better. Johns Hopkins specifically cautions that 24-, 36-, 48-, and 72-hour fasts are not necessarily more effective and may be dangerous for some people [1].
Key takeaways
- A 36-hour fast is an extended fast, not a beginner default.
- Possible benefits depend on the overall eating pattern, not the fasting window alone.
- Side effects can include fatigue, headache, dizziness, nausea, irritability, low energy, and trouble concentrating [2][3].
- People who are pregnant or breastfeeding, under 18, underweight, managing diabetes, taking medication, or living with a current or past eating disorder should avoid extended fasting unless guided by a qualified clinician [1][3][4].
- Breaking a 36-hour fast gently matters. A very large first meal can feel uncomfortable.
- If a 36-hour fast causes unsafe symptoms or rebound eating, a shorter schedule may be a better fit.
Table of Contents
What is a 36-hour fast?
A 36-hour fast is a fasting window that lasts about a day and a half. It is often arranged around sleep so that you skip one full day of eating.
| Example schedule | What happens |
|---|---|
| Monday 7 p.m. | Finish dinner and begin fasting |
| Tuesday | Fast through the day |
| Wednesday 7 a.m. | Break the fast with breakfast |
That is different from 16:8, where you fast for 16 hours and eat within an 8-hour window each day. It is also different from a 24-hour fast, which usually runs from one meal to the same meal the next day.
Because 36 hours is longer and more disruptive, it deserves a higher safety bar. If you have only tried short overnight fasting, a 36-hour fast is usually too large a jump.
What may happen during a 36-hour fast?
Most people notice the practical effects first: hunger, changes in mood, lower energy, more thoughts about food, or a strong desire to eat when the fast ends. Some people feel steady for part of the fast and then hit a harder stretch later.
Johns Hopkins describes intermittent fasting as switching between fasting and eating on a regular schedule and notes that after hours without food, the body uses stored energy differently [1]. That does not mean every longer fast produces better results. Going longer can also make the routine harder to tolerate.
Possible experiences during a 36-hour fast include:
- hunger that comes and goes
- fatigue or low energy
- headache
- dizziness
- irritability
- nausea
- trouble concentrating
- feeling cold
- stronger cravings when the fast ends
Mayo Clinic notes that intermittent fasting may cause tiredness, dizziness, headaches, mood changes, constipation, diabetes management issues, and menstrual effects [3]. Cleveland Clinic describes 24-hour fasting methods as more likely to bring stronger symptoms such as fatigue, headaches, irritability, hunger, low energy, nausea, weakness, and trouble concentrating [2].
Are there benefits to a 36-hour fast?
A 36-hour fast may help some adults reduce eating opportunities or create a clearer reset after a period of grazing. But it should not be treated as a reliable upgrade over shorter fasting windows.
For weight-related goals, the key question is whether the pattern helps you sustain an overall calorie pattern without rebound eating, poor nutrition, or unsafe symptoms. A 2026 Cochrane review found that intermittent fasting may make little to no difference to weight loss compared with traditional dietary advice in adults with overweight or obesity [5].
That does not mean fasting cannot help anyone. It means the fast itself is only one part of the routine. Meal quality, total intake, activity, sleep, stress, medication needs, and consistency all matter.
For many people, a shorter approach such as 14:10, 16:8, or occasional 24-hour fasting is easier to evaluate than jumping straight to 36 hours. If you are comparing longer fasts, read about when longer fasts may be too much before making the window more restrictive.
How often should you do a 36-hour fast?
There is no universal schedule. For most people, a 36-hour fast should not be a frequent default. If someone chooses to try it, it is better treated as an occasional advanced experiment, not a routine punishment for eating more than planned.
Be especially cautious if a 36-hour fast makes you:
- overeat when the fast ends
- skip balanced meals on non-fasting days
- feel anxious about breaking the fast
- push through dizziness or weakness
- extend the next fast to compensate for a meal
- ignore medication, training, work, or family needs
If those patterns appear, the fast is not helping. A shorter fasting window with more consistent meals is likely a better next step.
How to prepare for a 36-hour fast
Preparation starts before the fast. Do not enter a 36-hour fast after a very low-calorie day, heavy alcohol intake, poor sleep, illness, or unusually hard training.
Before starting, ask:
- Have I tolerated shorter fasts without symptoms?
- Can I drink enough water during the fast?
- Is my schedule low-stress enough for a longer fast?
- Do I take any medication that requires food?
- Do I have diabetes, blood sugar concerns, or a history of fainting?
- Am I using fasting to support a routine, or to compensate for eating?
Your last meal should be normal and nourishing, not a huge "last chance" meal. Include protein, fiber-rich carbohydrates, vegetables or fruit, healthy fats, and water.
If you track routines, GoFasting can help you log fasting windows, water intake, weight, steps, and calorie intake while you review whether shorter or longer windows are actually repeatable. Use tracking as feedback, not pressure to finish an unsafe fast.
How to break a 36-hour fast
Break a 36-hour fast gently. You do not need a complicated protocol, but you should avoid making the first meal extremely large, greasy, or mostly sugary.
Good first-meal options include:
- eggs with vegetables and toast
- Greek yogurt with berries and oats
- lentil soup with salad
- tofu or chicken with rice and vegetables
- salmon, potatoes, and greens
- cottage cheese with fruit and nuts
Eat slowly and stop before you feel uncomfortably full. If your stomach feels sensitive, start with a smaller balanced meal and eat again later.
For more detail on food choices after fasting, see how to break a fast safely and foods that help you start steady before fasting.
When a 36-hour fast may not be the right fit
Avoid a 36-hour fast unless a qualified healthcare professional specifically guides you if you are:
- pregnant or breastfeeding
- under 18
- underweight, malnourished, or recovering from illness
- living with a current or past eating disorder
- managing diabetes or blood sugar instability
- taking insulin, glucose-lowering medication, or medication that must be taken with food
- dealing with kidney disease, heart disease, liver disease, or another chronic condition
- experiencing frequent dizziness, fainting, or low blood pressure symptoms
Stop the fast and seek guidance if you develop fainting, severe dizziness, confusion, chest pain, persistent weakness, vomiting, severe headache, symptoms of low blood sugar, or symptoms that feel unsafe.
The point is not to prove that you can complete 36 hours. The point is to choose a pattern that supports your health and daily life.
FAQ
Is a 36-hour fast good for weight loss?
It may help some people reduce eating opportunities, but weight loss may not happen for everyone. Evidence does not show intermittent fasting is clearly superior to traditional dietary advice for weight loss [5]. Rebound eating can erase the intended calorie reduction.
What can I drink during a 36-hour fast?
Water is the simplest default. Johns Hopkins lists water, black coffee, and tea as common fasting-window options [1]. Avoid alcohol and calorie-containing drinks during a strict fasting window.
Is a 36-hour fast better than a 24-hour fast?
Not automatically. A 36-hour fast is more restrictive and may be harder to tolerate. Longer fasting is not necessarily more effective and may be dangerous for some people [1].
Can beginners do a 36-hour fast?
It is usually not a beginner default. Most beginners should start with shorter windows, such as 12:12, 14:10, or 16:8, and only consider longer fasts if shorter schedules feel stable.
What should I eat after a 36-hour fast?
Choose a balanced meal with protein, fiber-rich carbohydrates, vegetables or fruit, healthy fats, and water. Avoid making the first meal extremely large.
Bottom line
A 36-hour fast is an advanced fasting pattern. It may appeal to people who want a more defined reset, but it is not automatically more effective than shorter schedules and may be unsafe for some people.
Start with safety, not the longest possible window. If you try a 36-hour fast, prepare with balanced meals, hydrate, break the fast gently, and stop if symptoms feel unsafe.
Medical disclaimer
This article is for general education only and is not medical advice. Speak with a qualified healthcare professional before trying a 36-hour fast, especially if you are pregnant, breastfeeding, under 18, underweight, taking medication, managing diabetes or another chronic condition, or have a current or past eating disorder.
References
- Johns Hopkins Medicine. Intermittent Fasting: What Is It, And How Does It Work? URL: https://www.hopkinsmedicine.org/health/wellness-and-prevention/intermittent-fasting-what-is-it-and-how-does-it-work
- Cleveland Clinic. Intermittent Fasting: What It Is, Benefits and Schedules. URL: https://health.clevelandclinic.org/intermittent-fasting-4-different-types-explained
- Mayo Clinic. Intermittent fasting: What are the benefits? Published March 8, 2025. URL: https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/expert-answers/intermittent-fasting/faq-20441303
- Harvard T.H. Chan School of Public Health, The Nutrition Source. Diet Review: Intermittent Fasting for Weight Loss. URL: https://nutritionsource.hsph.harvard.edu/healthy-weight/diet-reviews/intermittent-fasting/
- Cochrane. Intermittent fasting for adults with overweight or obesity. 2026. DOI: 10.1002/14651858.CD015610.pub2. URL: https://www.cochrane.org/evidence/CD015610_intermittent-fasting-traditional-dietary-advice-or-no-treatment-which-works-better-help-adults