How to STAY in Ketosis After a Water Fast

Written by Ahmed Zayed | Last updated on August 11, 2023

Ever heard of water fasting? It's a practice where you abstain from consuming anything but water for a set period. 

The benefits are numerous, from detoxification to mental clarity. But what's the catch? 

After your water fast, the challenge lies in staying in ketosis, that prized state where your body burns fat for fuel. 

In this blog we will dive into the art of maintaining ketosis post-water fast, ensuring your health journey continues on a high note.

What is Ketosis?

Ketosis is a natural metabolic state in which your body switches from primarily using glucose (sugar) for energy to utilizing ketones, molecules produced from fat breakdown.[1]

This shift occurs when carbohydrate intake is limited, prompting the body to rely on stored fat as its main source of fuel. 

Ketosis is a cornerstone of low-carb diets and fasting, offering benefits like weight loss, improved energy, and mental clarity.

Benefits of Ketosis

Ketosis has several potential benefits, including:

  1. Weight loss: One of the biggest benefits of ketosis is weight loss. The process can help you feel less hungry, which may lead to eating less food. It can help you lose belly fat while maintaining lean mass.[2]

  2. Improved blood sugar management: Ketosis may help improve blood sugar management. It can also help reduce glycemic fluctuations.

  3. Reduced seizures in children with epilepsy: Ketosis may help reduce seizures in children with epilepsy.

  4. Increased focus and energy: Ketosis has been shown to increase focus and energy.

  5. Treating and managing diseases: Ketosis may help treat and manage diseases such as diabetes and degenerative disease.

What is Water Fasting?

Water fasting is a practice that involves abstaining from all types of food and caloric beverages, consuming only water for a defined period.[3]

It's a deliberate break from eating that allows your digestive system to rest and your body to tap into stored energy reserves. 

Water fasting is believed to have various health benefits, including detoxification, weight loss, improved insulin sensitivity, and potential cellular regeneration. 

It requires careful planning and monitoring to ensure safety and effectiveness.

How long does it take to go into ketosis when fasting?

The time it takes to go into ketosis when fasting can vary depending on several factors, including age, metabolism, exercise level, and current carb, protein, and fat intake.[4]

However, some general timelines are:

  • 12 hours: After 12 hours of not eating, the body may go into ketosis, which many people do overnight before they "break fast" with a morning meal.

  • 2-4 days: It typically takes 2-4 days to enter ketosis if you eat fewer than 50 grams of carbs per day.

  • 72 hours (3 days) or longer: Generally speaking, ketosis can be achieved by fasting for longer than 72 hours (3 days) or by following a very low carb (30-50g/day), keto diet for up to several weeks.

It's important to note that the speed at which someone enters ketosis can vary depending on factors such as physical activity level and carb intake. 

Benefits of Water Fasting

Water fasting is a type of fast that restricts everything except water. It has become more popular in recent years as a quick way to lose weight. 

Here are some benefits of water fasting:

  • Weight loss: Water fasting can help you lose weight, as it restricts calorie intake and forces the body to burn stored fat for energy. However, it's important to note that the weight loss may not be sustainable long-term.

  • Improved blood sugar control: Fasting may help maintain steady blood sugar and insulin levels throughout the day, which may optimize levels of human growth hormone (HGH).[5]

  • Reduced inflammation: Fasting has been shown to decrease inflammation in the body, which may help reduce the risk of chronic diseases such as cancer and neurodegenerative disorders.

  • Improved kidney function: Water is a natural appetite suppressant, and it helps improve kidney function by removing waste and toxins from your blood.

  • Improved skin health: Water fasting can improve skin hydration, which can lead to healthier skin.

However, it's essential to approach water fasting with caution, considering individual health conditions and seeking medical advice if necessary.

Safety Considerations for Water Fasts

Water fasting can be a risky practice, and it is not recommended for everyone. 

Here are some safety considerations for water fasting:

  • Limited research: There is very limited research on the health effects of water fasting. Therefore, it is important to approach water fasting with caution and seek guidance from a healthcare professional before attempting it.

  • Risks: Water fasting carries several risks, including dehydration, electrolyte and nutrient deficiencies, muscle loss, low blood pressure, mood changes, migraine headaches, and disordered eating. It can also make you feel physically and mentally drained.

  • Supervision: Water fasting should only be done under the careful supervision of a healthcare professional. This is especially important for people who are on blood pressure medications or have certain medical conditions such as type 2 diabetes.

  • Duration: If followed carefully and for no more than 72 hours, then water fasting can be considered safe. However, fasting for longer periods can be dangerous, especially when re-feeding the body after a long fast.

In conclusion, water fasting is not a safe practice for everyone, and it should be approached with caution. 

It is important to seek guidance from a healthcare professional before attempting it and to only fast under their careful supervision.

9 Ways To Stay in Ketosis After a Water Fast

  1. Don't Rush Reintroduction: Resist the urge to overload on carbs; reintroduce foods gradually.

  2. Don't Skimp on Healthy Fats: Don't cut back on essential fats; they're vital for sustained ketosis.

  3. Avoid Carb Overload: Steer clear of carb-rich foods that can kick you out of ketosis.

  4. Don't Skip Protein: Don't neglect protein intake; it's essential for muscle maintenance.

  5. Stay Clear of Sugar: Avoid sugary treats that can spike insulin levels and hinder ketosis.

  6. Don't Forget Hydration: Don't overlook hydration and electrolytes; they're crucial for ketosis.

  7. Don't Stay Sedentary: Avoid inactivity; regular exercise aids ketone production and metabolism.

  8. Mind the Macros: Don't disregard macronutrient ratios; they're key for sustained ketosis.

  9. Don't Stress or Skimp on Sleep: Prioritize sleep and stress management for optimal ketosis.

Frequently Asked Questions

What are the first signs of ketosis?

In the early stages of ketosis, you might notice increased thirst, dry mouth, and frequent urination. 

Your breath could develop a distinct fruity odor, and you may experience temporary fatigue or "keto flu" symptoms. 

Additionally, appetite suppression and improved mental clarity are common signs as your body adapts to using ketones for energy instead of glucose.

What being in ketosis feels like?

Being in ketosis often feels like heightened mental clarity and sustained energy levels. You might experience reduced hunger and cravings, contributing to easier appetite control. 

Physical signs could include increased urination and a dry mouth due to the diuretic effect of ketosis. 

Some people also enjoy a gradual weight loss while maintaining muscle mass. 

It's important to note that individual experiences vary; while many find ketosis invigorating, some may encounter temporary challenges like the "keto flu" as their bodies adjust to this metabolic state.

How do you trigger ketosis?

To trigger ketosis, limit your carbohydrate intake to around 20-50 grams per day. This depletion of carbs forces your body to use stored fat for energy. 

Include moderate protein and prioritize healthy fats. Fasting or practicing intermittent fasting can accelerate ketosis. 

Regular physical activity aids in depleting glycogen stores. Stay hydrated and manage electrolytes, as they are crucial. 

Remember, individual responses vary; monitoring ketone levels can help determine if you've successfully entered ketosis. 

Always consult a healthcare professional before making significant dietary changes.

How long do I need to fast to get back into ketosis?

The duration required to re-enter ketosis through fasting varies. 

Generally, it takes around 24 to 48 hours of fasting to deplete glycogen stores and transition into ketosis. 

However, individual factors such as metabolism, activity level, and previous dietary habits play a role. Keep in mind that entering and sustaining ketosis involves more than just fasting—it requires maintaining a low-carb, high-fat diet. 

Monitoring ketone levels can help gauge your progress. Consulting a healthcare professional before attempting extended fasting is advised, especially if you have underlying health conditions.


In conclusion, mastering how to STAY in ketosis after a water fast is the key to unlocking sustained benefits. 

By gradually reintroducing foods, prioritizing healthy fats, and monitoring your macronutrient balance, you can maintain this metabolic state. 

Remember to stay hydrated, exercise regularly, manage stress, and seek professional guidance if needed. 


  1. Ketosis. Retrieved from

  2. What Is Ketosis, and Is It Healthy?. Retrieved from

  3. Water Fasting: Benefits and Dangers. Retrieved from

  4. How Long Does It Take to Enter Ketosis?. Retrieved from

  5. 8 Health Benefits of Fasting, Backed by Science. Retrieved from

About the author 

Dr Ahmed Zayed is a medical resident specializing in plastic surgery with years of experience in the field. He is also a writer for top-rated websites including Washington Post, Chicago Tribune, ConsumerHealthDigest, and Huffington Post

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