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Can You Drink Diet Soda While Fasting?

Does diet soda break intermittent fasting? Can you drink diet soda while fasting? These are the questions you may also have if you’re new to intermittent fasting. The answer depends on different factors because generally, calories can break your fast. So, really zero-calorie diet soda can work. But there are also many alternatives to diet soda you can drink while fasting.

Can You Drink Diet Soda While Fasting?
  • Intermittent fasting is a simple approach to limit caloric intake.
  • You can only consume calorie-free foods and drinks while fasting.
  • Diet soda cannot break a fast but its artificial sweeteners can cause various health issues.
  • Water, black coffee, bone broth, and herbal tea are some of the healthy alternatives to diet soda while fasting.

What Is Fasting?

Fasting or intermittent fasting is an eating pattern that cycles between periods of eating and fasting. It doesn't dictate which foods to eat but rather when to eat them.

Intermittent fasting can be a useful approach to losing weight, improving metabolic health, boosting digestive health, and inducing autophagy, a cleaning process in human cells [1] [2].

Popular methods include:

Although each of these fasting methods has its rules and results, they all focus on restricting calories for health benefits.

The most important rule of intermittent fasting is to avoid calories during the fasting window, meaning that you cannot consume any foods but you can use calorie-free drinks.

Liquids to Drink while Fasting

The best liquids you can consume while fasting are the ones with zero or almost no calories, including the following.

  • Water: The number one choice to stay hydrated
  • Herbal Tea: Has no calories and can help curb hunger
  • Black Coffee: Calorie-free and can even help boost metabolism
  • Green Tea: Low in calories and rich in antioxidants
  • Sparkling Water: Zero calories and can increase satiety

Any drinks containing sugar, cream, milk, or other calorie-containing additives can break your fast. What about diet soda? Can you drink diet soda while fasting?

To see if diet soda can be used while fasting, we need to see what it is and what it includes and find out how it can affect intermittent fasting.

What Is Diet Soda?

Diet soda is a type of soft drink artificially sweetened using zero-calorie or low-calorie sweeteners instead of sugar, and is marketed as a lower-calorie or calorie-free alternative to regular soda.

The ingredients can vary depending on the brand, but common sweeteners used in diet sodas include aspartame, sucralose, and acesulfame potassium.

Other ingredients may include carbonated water, flavorings, preservatives, and sometimes caffeine.

So, can these ingredients break a fast?

Learn More: 20 Best Zero-Calorie Drinks: Are They Healthy for Weight Loss?

Can Diet Soda Technically Break Your Fast?

Technically, no, diet soda does not break your fast - if you’re fasting for calorie restriction or metabolic effects - because it has zero or few calories.

However, you need to consume diet soda in moderation and with caution because some artificial sweeteners may affect insulin response or hunger levels [3] [4] [5].

Does it mean diet soda can hinder weight loss?

Learn More: Do Medications Break a Fast?

Can Diet Soda Impact Your Weight Loss Efforts?

Many studies suggest that although diet soda is marketed as a healthy alternative to regular soda, it’s not that healthy or waist-line-friendly!

Yes, diet soda has no or few calories but it has no nutritional value, either. The table below shows the nutritional facts of 100 grams of diet soda [6].

Calories 0 kcal
Protein 0.1 g
Total Fat 0 g
Carbohydrates 0 g
Fiber 0 g
Sugars 0 g
Calcium 4 mg
Iron 0.04 mg
Magnesium 1 mg
Phosphorus 0 mg
Potassium 2 mg
Sodium 6 mg
Zinc 0 mg
Copper 0.025 mg
Selenium 0 µg
Vitamin C 0 mg

Please note that not all diet sodas are free of calories and sugar, and even not all artificial sweeteners are low in calories or sugar. Some contain both sugar and sweeteners, like Coca-Cola Life, stevia sweetener, 90 calories, and 24 grams of sugar in each can.

The problem is not that diet soda has no specific nutrients, but artificially sweetened drinks may cause different health problems, especially metabolic syndrome, which can lead to various issues like the risk of heart disease and diabetes, insulin resistance, belly fat, and high blood pressure.

A 2015 study on the links between consuming diet soda and waist circumference found that increased consumption of diet soda could increase abdominal obesity, which can raise cardiometabolic risk [7].

Another 2015 study indicated that diet soft drinks can increase the risk of metabolic syndrome, which can lead to weight gain [8].

A 2017 study on the effects of sugar and artificially sweetened drinks on weight gain found that there was a significant relationship between consuming sugar and artificially sweetened soda and obesity [9].

Artificial sweeteners in diet soda can even disrupt the body's natural ability to regulate calorie intake and hunger, leading to overeating and weight gain.

But that’s not all.

Learn More: Carnivore Diet Fasting

Other Side Effects of Diet Soda

Consuming diet soda can also lead to health problems, including:

  • Type 2 Diabetes
  • Cardiovascular Problems
  • Kidney Problems
  • Mental Issues
  • Dental Issues
  • Digestive Problems
  • Headaches
  • Osteoporosis 

Type 2 Diabetes

A 2018 study on diet soda and sugar content revealed that using artificial sweeteners in diet drinks does not lower the risk of diabetes, and diet soda can be an independent diabetes risk factor [10].

A 2015 study indicated that drinking sugar-sweetened beverages significantly increased the incidence of type 2 diabetes, independently of adiposity. Also, artificially sweetened beverages were not found to be healthy alternatives to sugar-sweetened drinks to prevent type 2 diabetes [11].

A 2009 study on the association between consuming diet soda and diabetes and metabolic syndrome found that daily intake of diet soda was associated with significantly greater risks of metabolic syndrome and type 2 diabetes [12].

A 2010 study on the safety of diet soft drinks indicated that individuals drinking diet soda every day have a higher risk of developing type 2 diabetes and metabolic syndrome, which includes high blood pressure, high cholesterol and triglyceride levels, insulin resistance, and excess abdominal fat [13].

Cardiovascular Problems

A 2016 study found that despite what many may think both sugar-sweetened and artificially sweetened beverages can increase the risk of hypertension [14].

A 2015 study on the connection between hypertension and artificially sweetened drinks suggested that there were statistically significant associations between consuming both sugar and artificially sweetened soda and hypertension [15].

A 2012 study found a direct link between drinking both artificially and sugar-sweetened beverages and the incidence of hypertension [16].

Kidney Problems

A 2017 study demonstrated that consuming diet soda was associated with a higher risk of end-stage renal disease (ESRD) in its population sample [17].

Mental Issues

A 2014 study on the relationship between the risk of depression and drinking coffee, tea, and sweetened drinks found that drinking coffee or tea with no sweetener was linked to lower depression.

Consuming artificially sweetened drinks showed higher risks of depression, i.e., regular intake of sweetened beverages, especially diet drinks, can raise the risk of depression among older adults [18].

A 2017 study on the connection between drinking diet drinks, coffee, and non-nutritive sweeteners and depression indicated that frequent consumption of coffee and non-nutritive sweetener use was directly linked to depression among populations in Atlantic Canada [19].

Dental Issues

Various studies, including a 2005 study indicated that too much consumption of carbonated drinks in the long term can cause erosion lesions. The acidity of diet soda can erode tooth enamel over time, leading to dental problems, such as cavities and tooth sensitivity [20] [21].

Digestive Problems

A 2010 study suggested that artificial sweeteners in diet soda may alter the composition of gut bacteria, which can negatively affect digestive health [22].


Individual reports show that some people experience headaches or migraines as a result of consuming artificial sweeteners found in diet soda.


A 2020 study revealed that both diet and regular cola can cause bone mineral density loss in women. The caffeine and phosphorus content in cola can disrupt normal calcium absorption, leading to mineral density loss and osteoporosis [23].

So, to avoid the negative effects of diet soda, we need alternatives to drink while fasting.

Learn More: What Is Fat Fasting?

Diet Soda Alternatives while Fasting

  • Water: The ultimate fasting-friendly beverage, keeping you hydrated without breaking your fast
  • Black Coffee: Zero-calorie and can help suppress appetite and boost metabolism
  • Herbal Tea: Calorie-free and comes in various flavors to satisfy different tastes
  • Green Tea: Low in calories and packed with antioxidants, providing a gentle energy boost
  • Sparkling Water: Refreshing with no calories or sugar
  • Bone Broth: Low in calories and can provide electrolytes and nutrients, especially in homemade varieties
  • Apple Cider Vinegar Drink: A tangy zero-calorie drink
  • Electrolyte Drinks: Zero-calorie electrolyte drinks that help maintain hydration and electrolyte balance during fasting periods
  • Plain Unsweetened Almond Milk: Low in calories
  • Lemon Water: A flavorful, calorie-free drink that can help digestion

Learn More: Can You Chew Gum While Fasting?

Can I Drink Diet Soda while Fasting for a Blood Test?

It’s best to avoid diet soda in addition to juice, coffee, soda, and other beverages before a blood test, as they can affect the results. The only 100% safe drink while fasting for a blood test is water.

Learn More: Coffee on a Carnivore Diet: Is It OK? The Best Coffee and Alternatives


So, the answer to the question, “Can you drink diet soda while fasting?”, is yes but you need to remember that diet soda may cause some negative health effects while not breaking intermittent fasting.

If you’re fasting to lose weight and gain health benefits, it’s better to adopt a healthy lifestyle and focus on natural drinks instead of industrial beverages that can negatively impact your health and fitness goals.

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