What to drink while intermittent fasting

Feb 9, 2024

Key takeaways

  • Intermittent fasting involves periods of fasting and eating.

  • What’s allowed during a fasting period depends on the type of intermittent fasting and your personal goals. 

  • It’s important to drink adequate water and electrolytes to prevent dehydration during any kind of fast. For autophagy to occur, avoid sugary drinks, including juice and smoothies, cow’s milk or plant-based milk, artificial sweeteners and alcohol during the time spent fasting. 

Intermittent fasting has become popular thanks to its potential health benefits, including weight management, improved metabolic health and longevity. It’s important to understand what you can drink during fasting periods in order to stay properly hydrated and support your overall well-being, without breaking your fast. 

ABCs of intermittent fasting 

Intermittent fasting is an eating pattern that alternates between periods of fasting and eating. There are various intermittent fasting methods which can be chosen based on your lifestyle and individual goals.

Common types of intermittent fasting include:

  • Time-restricted eating is based on a set amount of hours per day that you eat, such as 16:8, which involves eating for eight hours per day and fasting for sixteen (8). 

  • Alternate-day fasting involves eating normally on one day, and significantly reducing calorie intake or observing a complete fast (27).

  • 5:2 plan involves eating as usual for five days a week and consuming very limited calories (around 500-600) on the other two non-consecutive days (1). 

  • O.M.A.D is short for “one meal a day”. It involves fasting for 23 hours and eating all daily calories within a one hour window per day. 

Benefits of intermittent fasting

Giving your body a break from food and calorific drinks during fasting periods induces a metabolic shift, using fat as fuel instead of glucose. This has the potential to improve body composition and reduce the risk of a number of chronic diseases (2). It also gives your gut a moment to rest and your cells time to recover and renew, allowing them to function better (3). 

  • Weight management - after about 12 to 16 hours of fasting, a metabolic shift occurs which helps break down fat in the body (4). 

  • Enhanced insulin sensitivity which reduces the risk of type 2 diabetes (28). 

  • Improved brain function - fasting promotes the production of brain-derived neurotrophic factor (BDNF), a protein which protects against damage and inflammation (5). 

  • Autophagy: removing and recycling damaged or dysfunctional cells, promoting overall cellular health and improved healthspan (6).

What counts as breaking a fast?

A fasting window is generally deemed to be one where you refrain from calorie consumption, only drinking water and certain low-calorie beverages, such as herbal teas. However, this depends on the type of intermittent fasting you choose to undertake and your reason for fasting. 

Weight management 

Intermittent fasting tends to result in a reduction in calorie intake. By restricting the time during which you eat, you may naturally consume fewer calories, which can help you lose excess weight. In addition, during fasting periods the body also shifts from using glucose as a primary energy source to burning stored fat (7). 

Autophagy or digestive rest 

If it's autophagy (cell recycling and renewal) you’re going for, avoid all calories during fasting times. Fasting for longer periods (starting at 16 hours) is associated with the stimulation of autophagy (9). Stimulating insulin and mTOR (a protein that controls cell metabolism) activity by consuming calories or amino acids (protein building blocks) during a fast may potentially inhibit autophagy (10). 

Fasting gives your gut a break; reducing inflammation and enhancing the abundance and diversity of beneficial gut bacteria, which in turn, has been linked to better overall physical and mental wellbeing (11). 

If your aim is to improve gut health, avoid calories or anything that may stimulate the digestive process. This typically means only drinking water, water with electrolytes, or herbal tea during fasting times. Coffee is not typically recommended for a gut resting fast because it stimulates digestive processes (13). 

What can you drink during intermittent fasting?

Water ✅

Water regulates body temperature, lubricates joints, protects tissues and rids the body of waste (15). It’s important to drink enough water during both your eating and fasting periods for proper hydration. 

Daily fluid recommendations are around 3.6 litres for men and 2.7 for women (16). However this includes water obtained from food and beverages. Since about 20% of daily fluid intake comes from food and the rest from drinks, it makes it even more important to focus on water while intermittent fasting (17). 

It's also important to get enough electrolytes (sodium, calcium, chloride, potassium, magnesium) to offset the loss of electrolytes via the urine or sweat during fasting. In fact, the body actually loses more electrolytes during fasting due to the metabolic changes taking place in the body (18). Electrolytes are vital because they play crucial roles in maintaining proper hydration, nerve function and muscle contractions (19). It can be helpful to add electrolytes to your water, but if you are fasting, opt for the versions without sweeteners or additives. 

Black coffee ✅

Drinking coffee won’t break your fast, because black coffee only contains a few calories per cup. In fact, some research suggests that coffee can help enhance some benefits of intermittent fasting, such as reducing the risk of cognitive decline (21). However adding sugar, cream or other additives to your coffee during fasting times will disrupt your fast. (20). 

If your primary goal is gut healing, you may want to consider drinking herbal tea instead of coffee because the latter has been shown to stimulate gastrin, a hormone that causes movement in the gut (13). 

Tea ✅

Some tea is beneficial for fasting, particularly green tea, which is rich in antioxidants like catechins. Antioxidants help combat oxidative stress and inflammation in the body, promoting overall health and supporting fasting benefits (22). 

A few cups of plain tea (green tea, black tea, herbal tea) will also leave your fast intact. Again, avoid additives like sugar, honey, milk or cream. Many iced teas sold in shops tend to have sweeteners added, so steer clear of these during a fast. 

Drinks to avoid during intermittent fasting

Sugary drinks ❌

Regular consumption of sugar-sweetened beverages is linked to weight gain, obesity, type 2 diabetes, heart disease, kidney diseases, non-alcoholic fatty liver disease and tooth decay(23). Consuming sugary drinks such as fizzy drinks, tonics, fruit juices and energy drinks will all break your fast.

It’s best to avoid artificial sweeteners too. While they might appear to be an ideal solution for satisfying sweet cravings during intermittent fasting, some are known to impact a because they impact insulin levels (29). 

Fruit and vegetable juice ❌

While fruit and vegetable juice contain some vitamins and minerals, they also contain calories. These drinks also often lack fibre, which slows down the absorption of sugar by the body and contributes to feelings of fullness (24). The sugars in juice are naturally occurring, but they rapidly spike blood sugar levels. This results in an insulin response, interfering with autophagy. Even vegetable juice, which is lower in sugar, contains carbohydrates which can also disrupt the fasting state. 

Milk or milk substitutes ❌

Milk or milk substitutes, such as almond milk, soy milk or oat milk all contain calories and macronutrients that  break a fast. If your goal is weight loss, consider adding a small splash of unsweetened milk to your coffee or tea. 

Alcohol ❌

Alcohol contains calories which interrupts the fasting state. Alcohol is also a diuretic, meaning it can lead to increased urine production and potential dehydration, which is also a risk during fasting. 

Alcohol may interfere with fasting goals even if consumed during non-fasting hours. Depending on the amount consumed, it leads to fluctuations in blood sugar and insulin levels. Alcohol also increases inflammation and can lead to an imbalance in gut bacteria (25, 26). If you do drink alcohol, avoid drinking immediately before a fast. 


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