Does Stevia Break a Fast? The Science Explained Simply

Intermittent fasting is one of the most popular methods of dieting. It can help you lose weight, improve mental clarity, and boost energy levels. But it can be confusing to know exactly what you can put into your morning coffee without breaking your fast.

Stevia is a natural sweetener that some argue is fine to have during fasting, but others are strongly against having it. The last thing you want to do is put in a lot of work with fasting but have your results ruined just because you added stevia to your coffee.

So, can stevia break your fast? In my 20 years as a personal trainer and nutrition coach, I’ll break down why having a little bit of stevia is fine with intermittent fasting. Here, I’ll share with you the pros and cons of having stevia during your fasting window.

Why Stevia Doesn’t Break Intermittent Fasting

I’ve personally used stevia in my coffee for years while intermittent fasting for weight loss without losing any results. But be sure to check your stevia to make sure that no additives are included that could spike your blood glucose levels.

Stevia is from the stevia rebaudiana plant and is a non-nutritive natural sweetener that’s 200-300 times sweeter than table sugar.¹ It’s seen as a healthier alternative to artificial sweeteners like aspartame and sucralose.²

Despite this sweetness, stevia itself doesn’t contain calories.

Stevia also ranks 0 on the glycemic index (GI), having no measurable impact on blood sugar levels. Steviol glycosides are the active compound that provides sweetness, and it doesn’t contain any calories.

It is possible that stevia, despite being a zero-calorie sweetener, could still cause an insulin response. This is due to the cephalic response, which means your body could trigger an insulin response after consuming something so sweet in anticipation of a blood glucose spike.³

But there isn’t much (if any) research on this with stevia to prove this insulin response can create a physiological change big enough to break a fast. And even if it does cause an insulin response, it would be so small that it wouldn’t ruin your results.

If you have a sweet tooth and want to add a natural sweetener like stevia to your coffee, then go for it.

You’ll lose more weight in the long run if it helps stick to your intermittent fasting window for longer. However, some have said that using zero-calorie sweeteners like stevia can cause increased hunger and cravings.

Be Careful Which Stevia Product You Buy

Stevia was previously restricted in Europe before 2011 simply because there was still limited research at the time on its long-term safety. However, stevia has since been approved by the European Union (EU) as a sweetener.⁴

While stevia is good for weight loss as a sugar replacement, you should still be careful not to overconsume it. Many think using a zero-calorie sweetener like stevia gives them a “free ride” to eat or drink more food than they usually would.

But research has found stevia doesn’t blood sugar levels after eating (in fact, blood sugar was lower when consuming stevia), and doesn’t increase food intake.⁵

I personally prefer pure stevia extract or drops since they don’t have any of the thickening agents added. Stevia drops may say it has “natural flavors” added, which are usually citrus extracts or fruit essences to enhance the flavor. But these shouldn’t cause your blood sugar to spike and are added to cover stevia’s natural bitterness.

Many stevia products contain additive thickening ingredients like dextrose, maltodextrin, or sugar alcohols that contain some calories and carbohydrates. Food manufacturers add these ingredients as fillers or bulking agents in commercial products for easier use.

Here are a few common additives in stevia products:

• Dextrose: a simple sugar, with GI of 100
• Maltodextrin: high processed carbohydrate, with GI of 85-105
• Erythritol: a sugar alcohol, with GI of 0

You can see how using a stevia sweetener with either dextrose or maltodextrin could cause a higher blood sugar spike, thus breaking your fast. So, be sure always to check the ingredient label on your stevia product to know if you’re truly getting zero calories.

Here is a breakdown of many of the popular stevia sweetener products:

Truvia

Stevia in the Raw

Wholesome Stevia

SweetLeaf Stevia

365 Whole Foods Stevia

SweetLeaf Stevia drops

365 Pure Stevia Extract

Can Stevia Trigger Insulin?

Stevia will not trigger an insulin spike, and studies have actually found it can lower your blood glucose levels.⁶ This is due to stevia’s natural active compound that improve insulin sensitivity, pancreatic function, and glucose metabolism.

Another study found stevia contains compounds that can’t be broken down or absorbed in your gut.⁷ So stevia should pass right through your gut, and shouldn’t raise your blood sugar levels.

More studies have found consuming stevia daily didn’t elevate blood glucose or insulin responses.⁸ Researchers said stevia is a helpful tool for weight loss since it reduces calories without having to change your diet.

Consuming stevia can also help to reduce appetite. Studies have found that stevia can reduce hunger and thus calorie intake without affecting your blood sugar levels.^9,10

Researchers even found that having stevia before a meal had more of an effect on lowering hunger than water alone. Study participants ate less during their meals if they had stevia beforehand, improving weight loss.¹¹

So, you can safely add stevia to your coffee, green tea, espresso, or water without fear of it triggering an insulin and breaking your fast.

You need an insulin spike to break a fast, and since stevia prevents a raise in glucose, then it should be safe when intermittent fasting.

Will Stevia Break Autophagy?

Autophagy is your body’s natural recycling system. It’s a process where your cells clean themselves up by getting rid of the old, damaged ones and reusing them to make new, healthy cells.

You have to fast for at least 16 hours before the autophagy benefits really start to ramp up.¹⁷ Having a low-carb meal for your meal before starting your fast can help you activate autophagy sooner.

Low insulin levels are a key signal for autophagy, and high insulin will lower it. Having low insulin from fasting lowers mTOR, which is a major “block” of autophagy. mTOR is activated with carbs and proteins.¹⁸

The autophagy process is a lot less forgiving with consuming anything other than water. Any elevation in insulin or blood sugar levels could suppress autophagy.

Insulin suppresses autophagy because your body is signaled to focus on storing energy, instead of cleaning up your cells. So even a small insulin response could prevent autophagy, at least temporarily.

Autophagy is also highly sensitive to calorie intake. But since pure stevia is calorie free, then this shouldn’t cause autophagy to lessen.

Like earlier said, stevia (and any other calorie-free sweeteners) could cause a cephalic response, in which your brain releases insulin to prepare the body for digestion. This could also happen just by smelling or thinking about food, so it’s probably unlikely or at least very minimal impact.

If you want to consume stevia while fasting without it breaking autophagy, then use these tips:

• Have a small amount – only a few drops of stevia
• Have stevia later in your fast – insulin levels are higher in earlier stages of fasting
• Notice your reaction – individual response varies person to person, some may have a stronger insulin response than others.

The only way to know 100% for sure if stevia affects your blood sugar and insulin is to wear a glucometer and ketone blood tester. Otherwise, it’s best to follow the tips above or stick to a pure water fast to be certain stevia doesn’t break autophagy.

Does Stevia Break Ketosis?

Ketosis is when your body runs out of its fat stores for energy instead of sugars or carbs you’ve eaten. If you haven’t eaten enough carbs or sugars then your body switches to burning body fat stores instead.

Consuming too many carbs or sugars will break ketosis. Even small amounts of foods or drinks that contain sugars or carbs high on the glycemic index can spike insulin, kicking you out of ketosis.

The typical daily carb limit to stay in ketosis is 20-50 grams of net carbs.

Since pure stevia doesn’t contain any sugars, carbs, or calories, it shouldn’t break ketosis. But it could possibly break ketosis if other ingredients are added to the stevia product.

Yet, the amount of these additives like maltodextrin and dextrose is very small, so it’s unlikely a single serving won’t be anyway near enough to break ketosis.

As said earlier, there is a belief that anything so sweet, such as stevia, could cause an insulin release in anticipation of incoming food. But this spike probably doesn’t happen very often, and when it does, it’s probably so small that it’s not likely to break ketosis.

Many stevia products are mixed with sweeteners like maltodextrin, dextrose, and erythritol, which contain calories or carbs. This is why it’s always a good idea to check the ingredients label and try to use pure stevia products.

The GI of maltodextrin and dextrose is very high, with maltodextrin at 85-105 and dextrose at 100. This will cause an insulin response that could very well break ketosis. Go with a stevia product with erythritol if you are going to use one, it has a GI of 0 and has virtually zero calories.

Sweeteners That Don’t Break a Fast

Consuming zero-calorie sweeteners shouldn’t break a fast, especially if you’re fasting for weight loss and not following a pure water fast.

Even an artificial sweetener like sucralose and aspartame shouldn’t break your fast despite being chemically derived. They both contain zero calories and shouldn’t cause an insulin response in most people (but some can have a small insulin release).

But I’m not a big fan of chemically derived artificial sweeteners like sucralose and aspartame. There are studies and reports they can affect gut health and cause digestive issues.¹⁹ And they both have been linked to brain issues like triggering migraines, and causing possible neurological issues.²⁰

I prefer non-nutrivite natural sweeteners when intermittent fasting. These include:

• Stevia
• Monk Fruit
• Allulose

But the only way to know 100% for sure is to wear a glucometer and use a ketone blood tester. Some individuals may have different responses to sweeteners despite them containing zero calories or sugars and ranking 0 on the glycemic index.

Try stop using a sweetener during your fasting window if you haven’t been getting results. It’ll also help to kick the sugar addiction. These sweeteners are significantly more sweet than regular sugar, so they could cause your taste buds to adjust and give you a higher sugar craving.

Many like adding a sweetener and creamer to their morning coffee. This is perfectly fine and won’t break your fast if you’re doing it for weight loss.

You can also definitely add coffee creamer when fasting as long as you’re using the right ones. I prefer to use a keto coffee creamer that contains a C8 MCT oil or powder that is converted into ketones in your body, helping to kickstart the fat-burning ketogenic process.²¹