Which Sweeteners Can You Consume While Fasting?

by Lisa Batten, PhD, CPT, PN1

spoon of powder

As intermittent fasting continues to grow more in popularity, many people are left wondering "will this break my fast?". Everyone agrees that a water-only fast is the absolute best way to capitalize on the benefits of fasting, but it's pretty hard to stick with. The second best type of fast is one you can stick with. 

Low-calorie sweeteners are a pretty important part of a healthy lifestyle. They allow us to enjoy many of the indulgent things in life without sugar messing up our business. Not all sweeteners are created equally, so before using them during a fast, it's best to know how they impact your body. 

There is some controversy on the topic because it hasn't been closely studied. What we do know is that some sweeteners spike insulin and may disrupt the benefits of fasting such as gut health, fat loss, and autophagy. To make matters even more confusing, individual responses to certain sweeteners can vary. 

Whether or not you decide to include sweeteners into your daily life or fasting regimen is up to you. However, if you want to capitalize on the benefits of fasting it's best to know which sweeteners may break your fast and which ones are fast-friendly. 


This group of lab-made sweeteners includes the most commonly seen names.

  six assorted-flavor doughnuts

Sucralose (Splenda): Sucralose is a calorie-free sweetener that does not spike insulin in most people. Consuming sucralose can result in alterations of gut bacteria that can negatively affect glucose metabolism, resulting in weight gain. While fasted, there is no evidence that it interferes with autophagy. However, sucralose does stimulate digestion and may impede fat loss. 
Verdict: Not great for fasting. 

Aspartame (Equal): This popular sweetener is often seen in diet sodas. It acts in a similar way to sucralose in that it doesn't spike insulin but can negatively impact gut microbiome and glucose metabolism over time, leading to weight gain. Unlike sucralose, aspartame has a component called phenylalanine that interferes with autophagy.
Verdict: Not great for fasting. 

Diet Coke can

Maltodextrin: Commonly used for filler, flavor, or to prolong shelf-life in packaged foods. It often occurs alongside other sweeteners like stevia. While maltodextrin isn't exactly a sugar, it is a simple starch that causes massive insulin spikes comparable to sugar. Yes, I know, it's ridiculous. It also has calories that are around the same as sugar. As if this wasn't annoying enough, maltodextrin has also been shown to inhibit the growth of probiotic bacteria in the gut.
Verdict: AVOID! This may as well be sugar

Acesulfame k (acesulfame potassium, ace-k): Due to its weird name, you may have seen this substance on labels and not even realized it's a sweetener.  Acesulfame k is a highly popular calorie-free sugar substitute that also remains stable when heated. It is commonly mixed with other sweeteners due to its strong taste. Acesulfame k has had controversy in lab experiments where it was linked to cancer in rats and was also shown to damage thyroid through a byproduct produced during metabolism called acetoacetamide. Acesulfame k has been shown to disrupt gut biome and may lead to weight gain. It may spike insulin in some people and also impede fat loss efforts. It does not appear to have an effect on autophagy.
Verdict: Not great for fasting, not great for daily life. 

Saccharin: This extremely sweet sugar substitute is usually added to products alongside other sweeteners. It is slowly absorbed but may have some impact on insulin. It has also been shown to disrupt gut bacteria, negatively influence insulin response, and may result in weight gain over time. In lab studies, saccharin has been shown to cause inflammation of the liver and to inhibit the growth of probiotic bacteria in the gut. It does not appear to interfere with autophagy during a fasted state.
Verdict: Not great for fasting, not great for daily life.

Allulose: This newer sweetener is a welcomed addition to sugar substitutes. It does not spike insulin, it may accelerate fat loss, and it does not activate digestion or disrupt gut bacteria. It is eliminated from your body without being used as fuel or fermenting. All of these qualities make it an excellent option for getting a little sweet hit without breaking your fast.  
Verdict: Good for fasting.

bunch of lollipops


Sugar-alcohols are derived from plant products. They are more slowly metabolized and contain less than half of the calories of table sugar. 

Erythritol: A popular sweetener made from corn using enzymes and fermentation. It is very low calorie (.25 calories /gram) and does not spike insulin or interfere with autophagy. Consuming erythritol will activate digestion by stimulating proteins, so it is best avoided during a fast if your primary goal is gut health.
Verdict: Ok for fasting

Xylitol: This low-calorie (2.4 calories/gram) sugar-substitute is commonly used in beverages and gum. It is favored for gum due to its ability to reduce bacteria in saliva that causes tooth decay. Xylitol doesn't cause a major spike in insulin when consumed in lower quantities but may elevate it in large amounts. It activates digestion by stimulating hormones in the gut and may interfere with ketone production. It is also more caloric than some other options. There is no evidence that it interferes with autophagy.
Verdict: Ok for fasting in small amounts.

Maltitol: This highly sweet sugar-substitute is widely used in lower calorie foods. It has 2-3 calories per gram (sugar is 4 cal/g) and causes a spike in insulin levels similar to sugar. Furthermore, given that it's only about 80% as sweet as sugar, there isn't a big benefit to using it over sugar. Maltitol also has a reputation for it's bloating and laxative effect. Overall, it's a great substitute for sugar if you want the calories and insulin spike of sugar but also crave painful farts. As for fasting, it interferes with all of the positive benefits of fasting and definitely breaks a fast.
Verdict: Breaks a fast and is a terrible fart-inducing compound

pink smoke

Inositol: Made from glucose, this sugar-alcohol has half the sweetness of sugar and actually occurs naturally in your body. In addition to being used as a sweetener, it has also been investigated for the treatment of depression, panic disorder, and obsessive-compulsive disorder. It has a positive effect on insulin sensitivity and has been used to treat Polycystic Ovary Syndrome (PCOS). Other than activating digestion, it does not interfere with fasts and can actually improve glucose metabolism. 
Verdict: Great for fasting, great for daily life. 

Sorbitol: Mostly made from potato starch, this low-calorie sugar-alcohol is about 60% as sweet as sugar. It is slowly absorbed so it does not create a rapid spike in insulin but does raise insulin levels. It also activates digestion and can cause bloating and diarrhea. It does not appear to impact autophagy.
Verdict: Ok in very small amounts (i.e. gum)


Natural sweeteners offer alternative options for low-calorie treats seekers. They are derived directly from plants and offer options for people who would prefer less gut disruption. 

wooden ladle and chopping board with ginger during daytime

Stevia: Extracted from leaves of the stevia plant, this no-calorie sugar substitute has become extremely popular. Consuming stevia while fasting does not interfere with autophagy or digestion. Furthermore, stevia may improve insulin levels. It is completely safe for fasting so toss a little in your coffee or tea if you feel like it. 
Verdict: Excellent for fasting, excellent for daily life. 

Monkfruit: This antioxidant-rich sweetener is extracted from the monk fruit. The extract is 100-250 times sweeter than sugar and contains zero calories. It may cause a minimal insulin spike and could stimulate digestion which may slightly interfere with fasting, but these effects are very minimal. It does not appear to interfere with autophagy and is extremely rich in antioxidants. 
Verdict: Ok for fasting, great for daily life. 

Oligosaccharides: A zero-calorie sweetener made from probiotic plant fiber.  It is not digested in the gut, does not spike insulin, and does not disrupt autophagy while fasting. Consumption of oligosaccharides may even be beneficial to insulin response and even reduce the risk of diabetes
Verdict: Excellent for fasting, excellent for daily life. 


Table of sweeteners that are ok to consume while fasting

fast friendly sweeteners



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