How Long Can You Water Fast Without Losing Muscle?

You might worry about losing your muscles when using water fast to lose excess body fat or weight, considering you’re restricting food intake and only drinking water. After all, you require energy to maintain your muscles. So, how long can you water fast without losing muscle?

You can water fast without losing muscle for about 24 to 72 hours and gain health benefits, such as weight loss, lower blood pressure, and autophagy. However, if your fast lasts longer than three days, you should do so under a doctor’s supervision to avoid any health risks.

In the rest of the article, I’ll take you through the benefits and drawbacks of water fasting. I’ll also highlight who should not water fast and how to prepare for it. Keep reading to learn more.

Benefits of Water Fasting

You can reap several health benefits by adhering to the recommended water fasting period of 1-3 days, including the following:

  • Weight loss: You can lose a significant amount of weight through water fasting because you’re in a calorie deficit, which promotes weight loss. You’ll first lose water weight but shed off the excess fat weight over an extended period.
  • Promotes autophagy: It is the process through which old and damaged human cells are eliminated and replaced with new cells. As a result, autophagy slows the aging process and inhibits cancer cells from replicating quickly.
  • Lowers blood pressure: According to research, supervised water fasting for nearly ten days can help lower blood pressure for hypertension patients. This is because they consume less salt and only drink water, which helps regulate blood pressure.

Drawbacks of Water Fasting

Although water fasting seems safe, it can lead to several health issues, especially if practiced for longer than three days without medical supervision.

  • Loss of lean muscle mass: You can lose lean muscle mass if you practice water fasting for an extended period without professional medical guidance. When there is no food intake, your body usually uses the energy from your muscles to recharge itself.
  • Dehydration: When you only drink water, you may still become hydrated and have symptoms like dizziness, headaches, and weakness. This is because over 20% of your daily water intake comes from the food you consume. Fortunately, you can prevent dehydration by drinking more water than normal. 
  • Unsafe blood pressure changes: After water fasting, you may experience dizziness and risk of fainting, referred to as orthostatic hypotension. Therefore, you shouldn’t drive or perform strenuous tasks to prevent accidents or injury.

Who Should Not Water Fast?

You should not water fast if you have underlying medical conditions like chronic kidney disease, diabetes, and eating disorders because it can worsen things, causing severe health implications.

Additionally, the following people shouldn’t go on water fast.

  • GERD (gastroesophageal reflux disorder) and heartburn patients
  • Children or teenagers under the age of 18
  • Elderly (75 and older)
  • Pregnant or breastfeeding women

5 Tips on How To Prepare for a Water Fast

There are no specific dietary restrictions or meal plans to follow for a water fast because you only need to drink water and nothing else for a set number of days. Although it may sound easy, you must prepare thoroughly to avoid backing out or doing more harm than good to your body.

Let’s look at five preparation tips for a water fast.

1. Prepare Your Body and Mind for the Fast

You must prepare physically and mentally before performing water fast to avoid giving up or straining yourself. The good news about water fasting is that there are no specific starting instructions. 

However, you’ll need to prepare by limiting your intake of food and other drinks except for water a few days or weeks before fasting. It’s also recommended to start with a 1-day fast and work your way up to a 3-day fast.

Beyond the initial 3-day fast, you’ll require medical supervision to ensure your body’s vital signs are healthy and normal.

2. Make Sure You Have a Comfortable Setting and Time

Next, consider the setting and time you want to do a water fast. Plan your water fast for rest days when you’re in a comfortable setting away from work or other strenuous daily activities. 

If you want to start with a 3-day water fast, you can fast on the weekends from Friday through Sunday. You’ll have enough time and space to fast effectively without distractions.

3. Avoid Stressful Behavioral or Routine Changes

The last thing you want to do is add stressful behavioral or routine changes like heavy weightlifting and extreme HIIT (high-intensity interval training) because you may feel hungrier and more energy drained, forcing you to break your fast and eat.

However, you can do light exercises like walking, yoga, and meditation. Keep your body relaxed by getting plenty of rest every night and strictly drinking water on fasting days.

4. Stop Fasting if You Feel Unwell

Be cautious to stop water fasting when you feel unwell for a prolonged period, whether hours or days, especially when done under no medical supervision. 

The following are some serious warning indications that you should stop fasting.

  • Severe dizziness and muscle weakness
  • Stomach and reflux problems
  • Sudden fluctuation in blood pressure and heart rate

It’s normal to feel tired, hungry, and uncomfortable during the first days, but you shouldn’t feel unwell to the point where you can’t perform your daily tasks. If this happens, stop fasting and seek immediate medical help.

5. Refeed Properly After Breaking the Fast

When you break your water fast, add foods and drinks slowly and gradually into your diet to avoid refeeding syndrome and stomach problems such as indigestion and bloating. Start with soft foods like fruit juices or vegetable soup to prepare your digestive system.

You can progressively introduce all the other types of food, starting with lean sources of protein, vegetables, and fruits to refuel your body and muscles.


Water fasting can present benefits and drawbacks for your health, so you should consult your doctor and seek permission before attempting it to be on the safe side. However, water fasting for 24 to 72 hours is generally safe and won’t cause you to lose muscle.

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