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Can You Drink Water While Intermittent Fasting? (Yes, It’s Essential!)

Yes, you absolutely should drink water while intermittent fasting. In fact, proper hydration becomes even more crucial during fasting periods. When you’re not consuming food, your body still requires fluids to maintain essential functions. Water consumption supports your metabolism, helps manage hunger sensations, and prevents the negative effects of dehydration that can derail your fasting efforts.

Staying properly hydrated is one of the most overlooked aspects of successful intermittent fasting. Many newcomers to fasting mistakenly believe they should restrict all consumption during their fasting window, but this is incorrect and potentially dangerous.

Why Proper Hydration Is Critical During Fasting

Becoming dehydrated while fasting is easy to do and many people are not aware of this. So now you are probably wondering how much water to drink while intermittent fasting. 

When you are fasting, your body is breaking down stored supplies of energy in the form of glycogen (sugar) and fat. When your body breaks down glycogen for energy, you can lose a lot of water, meaning you should drink more liquids during your fasting window.

Additionally, the food we eat naturally contains water. This means that if you are fasting for an extended period of time, you are not getting water and the benefits of water you typically get while you are eating. 

Dehydration Risks: Why You Need More Water While Fasting

Dehydration during fasting can lead to several unwanted side effects that might make your fasting experience unpleasant. These include:

  • Increased hunger sensations
  • Headaches and dizziness
  • Difficulty concentrating
  • Fatigue and low energy
  • Constipation
  • Increased heart rate

The good news is that most of these symptoms can be prevented by maintaining proper hydration throughout your fasting window. Water helps maintain blood volume, supports brain function, and helps your body continue to flush toxins even when you’re not eating.

Also, read – 18/6 Intermittent Fasting: The Secret to Sustained Weight Loss

The Science Behind Water Loss During Fasting Windows

During fasting, your body undergoes several physiological changes that directly impact your hydration status. Without a regular intake of food, your body begins to tap into its stored resources for energy, which has direct implications for your fluid balance.

First, your insulin levels drop significantly when fasting, which causes your kidneys to excrete more sodium. This increased sodium excretion leads to greater water loss through urination. Second, as your body depletes its carbohydrate stores, it releases the water molecules that were bound to those carbohydrates.

How Glycogen Breakdown Affects Your Hydration Needs

One of the primary energy sources your body uses during fasting is glycogen, which is stored primarily in your liver and muscles. For every gram of glycogen your body stores, it also stores about 3-4 grams of water.

As your body breaks down this glycogen for energy during fasting, that stored water is released and eventually eliminated. This process alone can cause significant water loss during the early stages of a fast, especially if you’re new to intermittent fasting. This is why you might notice more frequent urination when you first start fasting.

It is recommended that the average adult drink 8 cups of water a day but try to drink one more cup for every hour you are fasting and go from there. You can adjust and drink less or more depending on how you feel.

This means if you’re following a 16:8 fasting protocol (16 hours fasting, 8 hours eating), you might aim for an additional 8-16 cups during your fasting window. However, personal factors like activity level, climate, and individual physiology will affect your exact needs.

A good rule of thumb is to drink enough that your urine remains pale yellow to clear. Darker urine is typically a sign that you need to increase your fluid intake.

Signs You’re Not Drinking Enough Water During Your Fast

Your body will give you clear signals if you’re not meeting your hydration needs during fasting. Watch for these warning signs:

  • Dark yellow or amber-colored urine
  • Dry mouth and lips
  • Feeling unusually thirsty
  • Headaches that worsen when standing
  • Dizziness or lightheadedness
  • Reduced elasticity when pinching your skin
  • Decreased mental clarity or brain fog

If you experience any of these symptoms, increase your water intake immediately. Severe dehydration can be dangerous, so don’t ignore these warning signs.

Hydration Tips: Making Water More Enjoyable During Fasting

This all being said, it is incredibly important to drink water during fasting periods. This will help ensure that you are staying hydrated and it can also help ward off hunger pains and feelings of tiredness. Try adding lemon or cucumber to your water for variety. Likewise, unsweetened herbal tea is another good alternative don’t forget about iced tea during the warmer parts of the year!

Here are some additional ways to make hydration more interesting during your fast:

  • Try sparkling water for a refreshing change
  • Add a few berries for subtle flavor (without breaking your fast)
  • Freeze herbal tea into ice cubes to add to your water
  • Include a pinch of salt for electrolyte balance
  • Try different herbal teas (hot or cold)

Avoiding Overhydration: Finding Your Perfect Balance

One thing to note, you want to make sure you are not drinking too much water because you may start to experience bad effects of water such as bloating and diarrhea. It is recommended that the average adult drink 8 cups of water a day but try to drink one more cup for every hour you are fasting and go from there. You can adjust and drink less or more depending on how you feel.

While rare, overhydration is possible if you consume excessive amounts of water without adequate electrolytes. This can lead to a condition called hyponatremia, where sodium levels in your blood become dangerously diluted. Signs of overhydration include:

  • Frequent, clear urination
  • Headaches
  • Nausea or vomiting
  • Confusion
  • Muscle cramping or weakness

The key is finding your personal hydration balance. Listen to your body and adjust accordingly.

Special Hydration Considerations For Active Individuals

Keep in mind that athletes and more active individuals are going to require more water and liquids than the average person and this doesn’t change if that individual is on a fasting diet.

If you exercise regularly while practicing intermittent fasting, your hydration needs will be significantly higher. Exercise causes additional fluid loss through sweat, and this fluid needs to be replaced to maintain performance and prevent dehydration.

For active individuals, consider adding electrolytes to your water during longer fasting windows, especially if you’re exercising during your fast. This can be as simple as adding a pinch of high-quality salt to your water or using a zero-calorie electrolyte supplement that won’t break your fast.

Tracking Your Water Intake During Intermittent Fasting

Keeping track of your water consumption can be particularly helpful when you’re fasting. Many people find that their normal thirst cues become less reliable during fasting periods, making it easier to become dehydrated without realizing it.

Consider these tracking methods:

  • Use a marked water bottle with time indicators
  • Track through a hydration or fasting app
  • Set regular reminders on your phone
  • Connect water intake to daily activities (drink after brushing teeth, before meetings, etc.)

The goal isn’t to force yourself to drink a specific amount regardless of how you feel, but rather to ensure you’re not forgetting to hydrate during your fasting window.

How Water Can Help Control Hunger During Fasting Windows

Drinking adequate water can be a powerful tool for managing hunger sensations during your fasting window. Sometimes, what we perceive as hunger is actually thirst, and having a glass of water can help determine if you’re truly hungry or just need hydration.

Water also helps fill your stomach temporarily, creating a sense of fullness that can reduce hunger pangs. This effect is enhanced if you sip warm water or herbal tea, which can be more soothing to an empty stomach than cold beverages.

Many experienced fasters find that staying well-hydrated is their number one strategy for comfortable and successful fasting. Remember that the question isn’t “can you drink water while intermittent fasting?” but rather “how much water to drink while fasting” to optimize your experience.

Asked by: Mary D.

Christine Richardson - Clinical Project Manager and Writer
Clinical Project Manager and Writer

With a Ph.D. in nutritional biology, Dr. Richardson is an expert in the field of nutrition, particularly intermittent fasting. Her dissertation project was an intermittent fasting study in athletes, which is where she gained substantial knowledge on the topic. She has contributed to a number of peer-reviewed articles spanning a wide array of topics and works as a freelance writer trying to make scientific knowledge accessible to the public.