What is Dirty Fasting?

8 min read

I’ve been dirty fasting for my entire life – and I didn’t even know it. I just recently came across this term while searching around the web. Therefore, I asked myself: What is Dirty Fasting?

Dirty Fasting works perfectly fine if your goal is to lose weight. With Dirty Fasting, you technically break your fast, but for losing weight it comes all down to the total calorie at the end of the day. If you put a little cream in your coffee, you won’t see a big change in your calories.

Keep reading to find out what the opposite of dirty fasting is, how much influence it has on your results, and more.


What exactly is dirty fasting?

I had no idea what the term dirty fasting is, but I soon realized that I’m doing it myself. I was a little shocked at first because I had no idea in what context “dirty” is. But it turns out it isn’t as bad as it sounds. After reading a couple of different opinions, I was not quite sure what to think.

When you start fasting and don’t want to break it, you’re usually limited to three drinks you can consume:

  • Water
  • Black Coffee
  • Tea (unflavored and unsweetened)

Now, if you allow yourself something other than that, for example, a cup of coffee with cream, you’re technically breaking your fast. The cream will cause a reaction by the body since it needs to digest it. The body will then start producing insulin – and break your fast. But you’re not really consuming any big calories. You won’t see a difference on your weight scale because you consumed a coffee with milk. This is called dirty fasting.


Is dirty fasting effective?

When it comes to losing weight, there is one big thing that will determine whether or not you will fail: Consistency.

I lost count of people on internet forums ranting about their diet and stopping it. Consistency is key to a successful weight loss journey, and if you like your coffee with a little bit of cream, then go ahead and have it. There are experts that argue if weight loss is your ultimate goal, then having a little cream in your coffee won’t really break the fast enough to cause any change in results. You are not stopping the fat loss. You might be slowing it down a bit, but I think this is much better than following a strict diet for a few months and then stopping it because you’ve had enough.


How does our body react to dirty fasting?

If you consume something that spikes our insulin, you break your fast. Simple, right?

Well, let’s take a look at how our insulin gets spiked. Whenever we eat or drink something, there is a rise in glucose or blood sugar. Our body will use that as energy. This result will cause the release of insulin in our body – and then break our fast.

Many people believe that replacing their sugar with zero-calorie sweeteners is the golden solution to an easy fasting window. Not so fast. Multiple studies show, that these sweeteners could still break your fast because your body thinks you are consuming sugar. As soon as he thinks that, he will go into preparation-mode to break down the incoming “sugar” – that’s why he will release insulin, and break the fast. But there are other studies that claim the opposite – sweeteners have zero calories, which is why it won’t cause an insulin response.

Should you consider sweeteners when fasting?equal sweetener

Yes – while some bad sweeteners might indeed cause an insulin spike, FDA registered ones won’t.

Sweeteners won’t break a fast if you…

  • …fast for metabolic health/weight loss
  • …fast for gut rest
  • …fast for longevity



This is a natural sweetener, and won’t inhibit the ability to burn fat or lose weight. So it won’t break your fast if you striving for fat loss and metabolic health. One review submits that stevia improves glycemic control and insulin sensitivity.


Monk Fruit

Monk fruit sweetener is derived from the monk fruit plant. Like stevia, it has no calories and no carbohydrates. It is 250-400 times sweeter than regular sugar. Its sweetness comes from mogrosides, an antioxidant that occurs naturally in monk fruit
I wrote a more detailed article about Monk Fruit and Fasting here.



This is an erythritol sweetener. This sweetener only provides 0.24 calories per gram, which is why it won’t have an impact on your body’s ability to burn fat. It tastes and bakes just like sugar. Not only is it zero-calorie & zero carbs, but it also has no bitter aftertaste.


Downfalls for dirty fasters

Are there any downfalls with dirty fasting?

Well, probably. There are no studies done on dirty fasting. But there are studies done on clean fasting, and it shows, that if you have no glucose (sugar, carbs) left to get used for fuel, your body starts burning fat. When your body has a rise in glucose, even just a little bit, it will start burning that instead of fat. But that doesn’t have to take hours. This could be a matter of minutes. Could! I’m not an expert, but I have done my research. While there are no studies done on this, many experts do believe that.

You see, it is kind of like an office building:

When all workers are gone, the cleaning crew starts to clean up (burn fat). They scrub the ground, and suddenly a worker (coffee with cream) comes back in with his dirty shoes (glucose). So instead of removing the dirt from the day, the cleaning crew goes after the worker to clean up after him. When they’re done cleaning up after him, they return to the other dirt. But once their shift ends, they leave, no matter if there is still dirt (fat) on the ground.

Will it delay your weight loss journey? Probably. Will it make you stop losing weight? No, it won’t. If you do everything else right, you will see the results on your weight scale very soon.


Difference between clean and dirty fasting

Clean FastingDirty Fasting
- Limited to water, black coffee, tea+ More freedom, can drink coffee with cream
+ Can also drink zero-calorie drinks+ Can also drink zero-calorie drinks
+ Can add zero-calorie sweeteners+ Can add zero-calorie sweeteners
- Consistency+ Consistency
+ Faster Results (maximal weight loss)- Results take longer


Should you clean or dirty fast?

You need to set your goals. If your goals are health, maximal weight loss, and maximal fat burning, then clean fasting is the best way to go. Why? Because that way you will see results much faster than with dirty fasting. If you decide to do dirty fasting long-term and don’t want to burn out quickly, you might want to consider adding some dirty fasting days. You can also try to do clean fasting for the first few weeks, and then evaluate if you can do this long-term. If you miss your morning coffee with cream, then don’t hesitate to mix some dirty fasting days into your week.


Do zero-calorie drinks break your fast?

Drinks are here to get you through your fasting window. While water, coffee, and tea can be good for a while, it will bore you at some point. Being bored from an intermittent fasting diet can be critical! That’s why I always have some zero-calorie drinks handy. Since they are zero-calorie, you won’t see a difference in your weight loss numbers.

I’ll list some drinks that I like below.

Just to note, all of the following drinks are:

  • Nothing artificial
  • Zero sugar
  • Zero calories
  • Non-GMO verified
  • Plant-based, Vegan and Gluten-free
  • No caramel color or any phosphoric acid


La Croix – Sprinkling Water

This is my go-to for a refreshing drink. Love it in the summer, but I’m also drinking it during the winter. Since you give up sugar during your fasting window, you might start to miss some taste in that clean water. Sometimes it’s just nice to pop a can open, and take a swig of something refreshing. I didn’t want to pay for some premium waters like Evian or Fiji, so I started with La Croix… and it is truly great. Now it’s your turn – try it out yourself. You can get a pack for around $22.00, and you’ll have enough for at least a month.

If you want to find out more about La Croix and Intermittent Fasting, make sure to read this article.


will lacroix break a fast


Zevia Zero Calorie Soda

Not only do I love the packaging – the variety pack was perfect to find what I like best. Healthy water – with a sweet taste. Overall I found the flavors that I like quite fast, and if you are unsure or if you’ve never had a Zevia Soda, go ahead and try the variety pack. The pack has 24 (!) cans for only $ 24.99. This will last for way over a month. You can buy it on Amazon here.

Are you interested in more information about Zevia and Intermittent Fasting? I wrote an article here.

will zevia break a fast

Can you drink coffee while intermittent fasting?

Yes, you’re safe to drink coffee while fasting. It won’t break your fast as long as you consume it black. That means no milk, no cream, and no sweeteners. Some people claim that drinking coffee makes you less hungry, which will make it much easier to stick to your fast. Flavored Coffee is also considered to be ok when dirty fasting.



Before starting intermittent fasting, set your goal. If you want to see fast results, go for clean fasting. If you want to stay consistent and have long-term benefits, go for some dirty fast days. You can make your fasting journey way easier by mixing in some zero-calorie drinks as well as some sweeteners. You might think you don’t need it now, but you will have a desire for new things during your fasting window after a few weeks

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8 thoughts on “What is Dirty Fasting?”

    • Hello Eleanor,
      Sugar-free powder Metamucil is generally safe if you are dirty fasting and should not break your fast.
      You can find more information about Metamucil and Intermittent Fasting here.


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