Don’t Break Your Fast! Your Complete Guide to Sweeteners

Hey there, fellow sweet tooth! There are so many reasons so many of us want to switch out over-processed table sugar for healthier alternatives. The recent focus on intermittent fasting and prolonged fasting for autophagy, gut rest, and fat loss is also making many of us question our choices in sugar-free sugar substitutes. But ultimately, we all know that sugar (oh, how sweet you are!) is just bad for us. {*}

So no matter what your reason for switching out sugar, it’s no easy task to understand which sugar alternative is actually bringing you closer to your goals. I did the work for you. Read below to get the down and dirty with all the applicable research now!

Nutritive Sweeteners, Non-Nutritive Sweeteners, and Sugar Alcohols

Nutritive sugars and sugar alternatives are those that provide a significant amount of energy in the form of calories when eaten. Nutritive sweeteners obviously include table sugar, honey, maple syrup, coconut sugar, agave. I will not cover them here as ultimately your body will process them as plain sugar. These do not fit into any type of fasting. However, this category also includes most sugar alcohols like xylitol, sorbitol, maltitol, and mannitol.

Sugar alcohols are a slightly different beast. They may be naturally-occurring or chemically-derived. Most sugar alcohols provide about 2 calories per gram consumed (regular sugar is 4 calories per gram). Many foods labeled as “sugar-free” or “no sugar added” actually contain sugar alcohols. They do contain carbohydrates, but the body does not fully absorb and metabolize sugar alcohols. That’s why if you consume large quantities of sugar alcohols, you could end up adding a lot of calories to your diet and suffer bloating, gas, and other intestinal upset (though your body should get used to it over time).

Non-nutritive sugar alternatives, on the other hand, are those that contain little to no calories. The food industry uses these heavily to make a range of diet products. They are generally much sweeter than sucrose (table sugar). Sometimes thousands of times as sweet. Common non-nutritive sugar alternatives include saccharine (found in Sweet N’ Low), acesulfame potassium (Sunett, Sweet One, Sweet ‘N Safe), aspartame (Equal, NutraSweet), sucralose (Splenda), luo han guo fruit extract (monk fruit), stevioside (Stevia in the Raw, Truvia, Stevia), allulose, and erythritol (sugar alcohol).

Allulose and erythritol deserve a separate mention on here. While they provide some energy, it’s at a minimal amount and therefore they may be considered non-nutritive.

Artificial Sweeteners

So now let’s address all of these to see if artificial sweeteners break a fast. Starting with the most common artificial sweeteners first. The artificial sweeteners listed below are all FDA-approved and are common lab-derived food additives found in many diet foods. It’s important to know that there is a lot of research highlighting the negative health impacts of many artificial sweeteners {*}. Therefore, my personal suggestion would be to avoid all of those when you can. Although, occasional use should likely pose no problems.

Does Aspartame Break a Fast?

What is aspartame? Aspartame is one of the most popular artificial sweeteners. Discovered back in 1965, it is a common additive to diet sodas and chewing gum. It’s about 200 times sweeter than sugar and goes under the trade names of NutraSweet, Equal, and Canderel.

It does contain an essential amino acid phenylalanine. Amino acids are protein molecules that stimulate mTOR. Basically, when mTOR goes up, autophagy goes down. This will break your fast if you are fasting for longevity. Aspartame actually stimulates your gut and alters gut bacteria so not good for gut rest fast. It also likely breaks a fast aimed at metabolic health and fat loss. Although it contains no sugar and won’t spike your insulin, recent studies show that consumption of aspartame over time may increase insulin resistance {*}.

• Fasting for Autophagy: Not Recommended
• Fasting for Fat Loss: Not Recommended
• Fasting for Gut Rest: Not Recommended

Does Sucralose Break a Fast?

What is sucralose? One of the most common sweeteners, sucralose (an ingredient in Splenda), is a sugar substitute that does not break down in the body and contains no calories. It’s produced through the chlorination of sucrose (plain sugar with chlorine, that’s right!). It’s also much sweeter than table sugar at 600 times the sweetness!

Sucralose will probably not break a fast aimed at autophagy since it contains no proteins and no energy. It also won’t break your fast if you are fasting for weight loss, as there is no insulin response to it. However, when used over longer periods of time, it does alter gut bacteria in a way that could also provoke insulin resistance {*}. Although it’s free of energy, most evidence points to eventual gain in body weight and increased risks of metabolic disorders including heart disease {*}. Due to that, it’s probably best to avoid it if you can.

• Fasting for Autophagy: Ok – Limited Quantities
• Fasting for Fat Loss: Not Recommended
• Fasting for Gut Rest: Not Recommended

Does Saccharin Break a Fast?

What is Saccharin? It’s the main ingredient in a popular sugar substitute Sweet N’ Low. Research shows that it may affect gut bacteria, so probably not the best choice for a gut rest fast {*}. It does not appear to interfere with autophagy. From a weight-loss perspective, however, it appears to influence the insulin response over time and may eventually lead to weight gain {*, *}. Similar to sucralose above, best avoided.

• Fasting for Autophagy: Ok – Limited Quantities
• Fasting for Fat Loss: Not Recommended
• Fasting for Gut Rest: Not Recommended

Does Acesulfame Potassium Break a Fast?

What is Ace K? Basically, this popular “flavor enhancer” and sugar substitute found in Sweet One. It’s about 200 times sweeter than sugar. Ace K may disrupt the gut biome. It also has been shown to spike insulin in humans and may lead to weight gain over time {*, *, *}. So if you want to burn fat, best to avoid it. However, it doesn’t contain any calories or nutrients and thus likely does not interfere with autophagy.

• Fasting for Autophagy: Ok – Limited Quantities
• Fasting for Fat Loss: Not Recommended
• Fasting for Gut Rest: Not Recommended

Natural Sweeteners

These are the sweeteners that are either found in nature or naturally derived. It is important to note, however, that all of them have to undergo some processing to make it to the store shelves.

Does Stevia Break a Fast?

What is Stevia? Stevia sweeteners come in liquid, grain, and powder forms. Stevia extract is about 200 times sweeter than sugar. It comes from the leaves of the stevia plant mostly grown in Brazil. Specifically, stevioside and rebaudioside A (reb A) are the most common sweet components of the leaf extracted. Stevia does not have an impact on the gut biome. Stevia does not raise blood glucose and does not spike insulin {*}. Stevia may aid in weight loss without negative side effects over long-term use {*}. It’s also my personal favorite in black coffee during an intermittent fast or a more extended fast. And if you’re worried that coffee breaks a fast, I direct you to this paper that concludes that coffee actually stimulates autophagy and fat breakdown {*}.

• Fasting for Autophagy: Recommended
• Fasting for Fat Loss: Recommended
• Fasting for Gut Rest: Recommended

Favorite Stevia Products

• SweetLeaf Organic Sweet Drops – Flavored Stevia Sweetener – English Toffee is totally a favorite, but they are all great!
• SweetLeaf Natural Stevia Sweetener Packets – Pure Stevia with Inulin (this is a fiber that has many benefits including the ability to stabilize blood glucose and enhance the gut environment!) If you don’t mind the taste of Stevia, this is the one I buy and use most often.

Does Monk Fruit Break a Fast?

What is monk fruit? Monk fruit is a fruit called Lo Hun Guo or Swingle Fruit. It is native to China. It has been used for many centuries in Eastern medicine. Mogrosides are the specific compounds in the fruit that give it its sweetness. Monk fruit has not been studied much in humans yet. However, current animal studies suggest that it may have an impact on the gut biome and may produce a slight spike in insulin levels {*}. On the up-side, however, monk fruit contains no calories and is very high in antioxidants that may actually help stimulate autophagy.

• Fasting for Autophagy: Recommended
• Fasting for Fat Loss: Not Recommended
• Fasting for Gut Rest: Not Recommended

Favorite Monk Fruit Products

• It’s Just – 100% Monkfruit Extract Powder, Non-GMO, 25% Mogrosides, Non-Glycemic – Pure Monk Fruit with one of the highest concentrations of Mogrosides (the sweet part of the Monk Fruit).
• Lakanto Monkfruit Sweetener with Erythritol – This sugar-free replacement blend tastes so good!
• Wholesome Yum Keto Coffee Syrup – Sugar-Free Syrup with Monk Fruit & Allulose, Non-GMO, Gluten-Free – This is an amazing product made by a good friend! Perfect if you’re looking for a syrup to add to your coffee that’s not Stevia-based. Comes in Vanilla or Hazelnut flavors. Yum!

Does Allulose Break a Fast?

What is allulose? Allulose is a fairly new sweetener that is actually only 70% as sweet as sugar. It’s naturally present in several foods like corn, fruit, and maple sugar. It was first discovered in the 1940s, but only recently came on the market as a low-calorie sweetener. It’s similar to fructose but does not get metabolized by your body. Although it contains some energy at 0.2 – 0.4 calories per gram, it does not affect insulin and blood sugar levels {*}. It probably breaks gut rest fast as the body does metabolize it. For autophagy and longevity, it is probably okay as it does not contain any amino acids (protein) and is a very low-calorie sweetener.

• Fasting for Autophagy: Recommended
• Fasting for Fat Loss: Recommended
• Fasting for Gut Rest: Not Recommended

Favorite Allulose Products

• Wholesome Yum Besti Keto Powdered Allulose Sweetener, Non-GMO – This is a pure allulose sweetener that dissolves great, and does not contain trace amounts of corn. It is derived using a natural fermentation process from different plants.
• Wholesome Yum Keto Maple Syrup – Sugar-Free Pancake Syrup With Monk Fruit & Allulose – So this is a blend and I know it’s maple syrup. But who says you can’t use Maple Syrup in your coffee?!

Sugar Alcohols

Does Erythritol Break a Fast?

What is erythritol? Erythritol forms naturally in small quantities in some foods like dried fruit. It is almost calorie-free at roughly 0.24 calories per gram. It’s only partially absorbed and digested by the intestinal tract, but due to that is a no if you are fasting for gut rest. In studies, it does not appear to stimulate insulin nor raise blood sugar {*}. It does not contain proteins and has very little energetic value, so it’s likely okay for fasting for longevity.

• Fasting for Autophagy: Recommended
• Fasting for Fat Loss: Recommended
• Fasting for Gut Rest: Not Recommended

Favorite Erythritol Products

• Anthony’s Erythritol Granules, 2.5 lb, Non-GMO, Keto & Paleo Friendly – I really like this brand if you are looking for non-GMO options.
• Whole Earth Erythritol – Pure erythritol with sugar-like texture.
• Besti Monk Fruit and Erythritol Blend – Powdered Sugar Replacement, Non-GMO – This is a great blend in a powdered form to ensure easy blending.

Does Xylitol Break a Fast?

Because xylitol does not contribute to cavities and gum disease, you can often find it in sugar-free gum. Since most sugar alcohols do contain about half the energy of regular table sugar, it probably isn’t a great alternative to consume in large quantities during a fast. For the same reasons, it isn’t great for a gut rest. Nor is it great in large quantities if you are fasting for autophagy. There is some insulin response, but it’s quite small {*}.

• Fasting for Autophagy: Ok – Limited Quantities
• Fasting for Fat Loss: Ok – Limited Quantities
• Fasting for Gut Rest: Not Recommended

Favorite Xylitol Products

• NOW Foods, Xylitol, Pure with No Added Ingredients, Keto-Friendly, Low Glycemic Impact, Low Calorie – I would be careful with Xylitol for any kind of fast, but small quantities should not kick you out of autophagy or ketosis.

Does Sorbitol Break a Fast?

Sorbitol acts similarly to xylitol. Your intestines can partially digest sorbitol, so it probably is not great for a gut rest fast. Sorbitol contains half the calories of table sugar and may impact insulin {*}, and thus should not be consumed in large quantities for fat loss or autophagy. But limited quantities found in sugar-free gum should not be a problem. Just watch out for bloating and other digestive issues common to all sugar alcohols.

• Fasting for Autophagy: Ok – Limited Quantities
• Fasting for Fat Loss: Ok – Limited Quantities
• Fasting for Gut Rest: Not Recommended

XO, Marina

Disclaimer: I am not a medical doctor or Registered Dietitian. The information presented is not medical advice. It is purely to share my experiences and opinions based on the linked research. As always, check with a doctor before making any fitness or nutrition changes. The author and blog disclaim liability for any damage, mishap, or injury that may occur from engaging in any activities or ideas from this site.