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Can You Drink Water While Fasting?

"Nora Minno is an award-winning New York-based registered dietitian, certified dietitian nutritionist, and certified personal trainer specializing in wellness communications and marketing. For over ten years, she has consulted for several national publications and CPG companies, offering the latest advice in nutrition and fitness, and appears regularly on the Emmy-nominated Daily Burn 365 as well as the DailyBurn HIIT app."

The short and sweet answer: Yes…but it depends.

Before we dive deeper into whether or not you can drink water during intermittent fasting, it’s important to understand the basic science behind intermittent fasting and what makes it effective.

What is Intermittent Fasting?

Intermittent fasting (IF) refers to a dietary pattern in which you alternate periods of eating and fasting (or significantly reducing your caloric intake). Intermittent fasting doesn’t refer to a specific diet type (i.e. keto, vegetarian, or low-carb) that tells you what to eat, but instead provides a framework for when to eat. This allows individuals to choose a pattern that works for them and their lifestyle.

There are a variety of different intermittent fasting plans to choose from including:

  • 16:8 – Fast for 16 hours, eat within an 8-hour window
  • 20:4 aka The Warrior Diet – Fast for 20 hours, eat within a 4-hour window
  • 5:2 fasting – Eat normally 5 days a week and consume a reduced calorie diet the other 2 days per week

While people may choose to practice intermittent fasting for a number of reasons, most people do so for the potential health benefits including:

  • Weight loss [1]
  • Improved insulin sensitivity [2]
  • Supporting brain health [3][4]
  • Improving heart health markers, such as the reduction of LDL [5]
  • Reducing inflammation [6]
  • Appetite control [7]

Depending on the type of IF you practice, intermittent fasting may have different effects on the body. For example, some studies show that by reducing the number of hours in which you eat throughout the day, you are more likely to consume fewer calories, and therefore weight loss may occur.

Many of the metabolic benefits of intermittent fasting are dependent on the body being in a fasted state. Consuming foods or beverages that contain calories from carbohydrates, fat, or protein can interrupt the body’s fasted state. In other words, eating or drinking calories signals the “on” switch for your body’s endocrine and digestive system and it immediately must go back to work breaking down and sorting out carbohydrates, protein, and fat.

Does Water Break A Fast?

Since it is calorie-free and doesn’t raise blood sugar levels, drinking good old H20 won’t break your fast!  In fact, drinking water while intermittent fasting is encouraged to maintain adequate hydration status.

The only exception to this rule is if you are practicing dry fasting. It restricts both food and liquid, therefore, drinking water while fasting is not allowed. People may practice dry fasting for religious or medical reasons, but since abstaining from water for a prolonged period of time can lead to dehydration, it’s advised to consult with a medical professional before dry fasting.

If you are required to dry fast prior to a medical procedure, be sure to check with your doctor to understand exactly how long you need to abstain from foods and fluids, since it may vary based on procedure. [NM1] 

What Types of Water Can I Drink While Intermittent Fasting?

So plain water is ok outside the eating period, but what about with lemon, flavored ones, seltzers?

The general rule of thumb is:

  • Zero-calorie and zero-sugar beverages are ok to drink;
  • Caloric and sweetened beverages are NOT ok to drink.

The great news is that there are plenty of zero-calorie options to keep you hydrated.

The types of water to drink that are ok include:

  • Plain Water – any temperature
  • Mineral Water
  • Unsweetened Flavored Seltzer Water
  • Unsweetened Club Soda or Sparkling Water
  • Unsweetened Flavored Still Water
  • Unsweetened Lemon Water

The types of liquids not to drink include:

  • Protein Waters
  • Sweetened Sparkling Waters
  • Sweetened Flavored Waters
  • Lemon Water with Added Sugar (i.e. honey or agave)

If you’re opting for a liquid other than plain H20, be sure to check the nutrition facts panel to make sure there is no added sugar or even protein.

The Health Benefits of Drinking Water While Intermittent Fasting

Drinking fluids during fasting is not only allowed – it’s recommended!

About 60-70% of the human body is made up of water, so drinking it and staying hydrated is crucial for supporting a number of important functions including:

  • Physical & Mental Performance [8]
  • Digestion [9]
  • General Energy Levels
  • Kidney Functions [10]

Drinking adequate amounts of liquids while practicing IF can also help manage feelings of hunger during fasting periods.

So how much water per day is considered enough? The Institute of Medicine recommends the following for adults (ages 18-70):

FEMALE    2.2 L or 9 cups as total beverages including water
MALE  3.0 L or 13 cups as total beverages including water

Source: Institute of Medicine

If you participate moderate or vigorous exercise, you will likely want to consider increasing your daily fluid intake to replenish water and other nutrients lost via sweat.

The recommendations above are for total fluids per day – so let’s see what else can help you reach your daily fluid goals while practicing IF.

What About Other Beverages While Intermittent Fasting?

The great news is that there are plenty of options that you can drink when fasting including:

  • Black Coffee
  • Unsweetened Hot or Iced Tea
  • Diet Sodas
  • Apple Cider Vinegar
  • No-Calorie Sports Drinks

Remember, it’s important not to drink sweetened or calorie-containing drinks during while the fasting period. Examples of beverages to avoid include:

  • Alcohol
  • Full-Sugar Sodas
  • Milk (Dairy and Non-Dairy)
  • Sweetened Sports Drinks
  • Protein Shakes
  • Smoothies
  • Sweetened Teas or Iced Teas
  • Juices

Once your fasting window ends, feel free to consume beverages of your choice that align with your nutritional goals or preferences.   
 

[1] https://content.iospress.com/articles/nutrition-and-healthy-aging/nha170036

[2] https://www.sciencedirect.com/science/article/pii/S1550413118302535

[3] https://www.researchgate.net/publication/341802201_Intermittent_Fasting_and_Brain_Health_Efficacy_and_Potential_Mechanisms_of_Action

[4] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3670843/

[5] https://pubmed.ncbi.nlm.nih.gov/19793855/

[6] https://www.cell.com/cell-metabolism/fulltext/S1550-4131(18)30253-5?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS1550413118302535%3Fshowall%3Dtrue

[7] https://onlinelibrary.wiley.com/doi/abs/10.1002/oby.22518

[8] https://cdn-00.cteonline.org/resources/documents/b0/b0972d53/b0972d5361d9225a561e305057d2a520e0e7d59e/HydrationArticle2.pdf

[9] https://www.cambridge.org/core/journals/british-journal-of-nutrition/article/mild-dehydration-impairs-cognitive-performance-and-mood-of-men/3388AB36B8DF73E844C9AD19271A75BF#

[10] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5646211/

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