Clean Vs Dirty Fasting: What's The Difference?

If you've tried a variety of diets and still can't seem to shed the pounds, you may be considering checking out the relatively new weight loss trend: dirty fasting. Fasting typically refers to totally or partially abstaining from all foods, through means like restricting calories, only consuming food every other day, and reducing your intake of certain macronutrients. Fasting has historically been associated with religion, as there are a number of faiths that include fasting as part of their belief. For example, Muslims fast during daylight hours for 28-30 days during Ramadan, and Greek Orthodox Christians restrict their diet during the 40 days before Christmas and Easter (via Nutrition Journal).

While fasting has historically been associated with these religions, it has become more part of the mainstream in recent years as a method for weight loss and other potential health benefits, according to the Cleveland Clinic. Intermittent fasting has become a popular option, and some people choose a combination of intermittent fasting, "dirty" fasting, and "clean" fasting.

But what exactly is dirty fasting? Is it safe? And how is it different from clean fasting?

What is dirty fasting and how is it different from clean fasting?

According to, while there are different points of view about what classifies a fast as "clean," and that clean fasting is not considered a medical term, they define a clean fast as "a fast when nothing other than water, black coffee, herbal teas, plain mineral water, or electrolytes is consumed. These additions to a fast are either non-caloric or extremely low in calories (≤5 calories), so they theoretically will not disrupt a fast through an insulin spike."

The main difference between a clean fast and a dirty fast is that a dirty fast provides a bit more leeway, allowing you to ingest artificial sweeteners, dairy products in your coffee or tea, and small amounts of protein. This bit of protein could come from sources like a cup of bone broth or a scoop of collagen powder in your morning drink. While this wouldn't be so much protein that it makes you feel full, the small amount would still be considered dirty fasting. If you are uncomfortable with attempting a clean fast, dirty fasting might theoretically be a bit easier in that it may make you feel less deprived.

How many calories are allowed?

While the definition for dirty fasting is still fluid, Healthline notes that dirty fasting is essentially a modified version of fasting, with people engaging in dirty fasting typically consuming 100 calories or less per day during a fasting window. While you inevitably do consume some calories during a dirty fast, the quantity is so far below what your normal daily intake is that there will inevitably be health benefits, such as weight loss.

However, at the end of the day, dirty fasting is not technically considered fasting by purists because of the intake of calories, even though they are minimal. That said, supporters of dirty fasting say this form of fasting isn't so substantial that it actually breaks a fast. Because of this, they claim it also makes it easier to keep to a fasting regimen, which is important when trying to maintain a new routine.

Does dirty fasting work?

There are a few different ways to fast, whether you're adding in a small amount of calories or not. Medical News Today outlines different ways to do intermittent fasting, one of which is by abstaining from food for 12-hour windows at a time, essentially splitting your day in half. Another is through the 16:8 method, which means fasting for 16 hours and only eating during an 8-hour window. Other options include fasting for two days out of the week, alternating the days you fast, and fasting for an entire 24-hour window once per week.

Proponents of clean fasting claim that going totally without food during the fasting windows has a myriad of health benefits that you just can't get when you're adding in some calories through dirty fasting, according to Healthline. Restricting calories entirely has been shown to promote autophagy, which is the "cleaning" of the body's cells that leads to healthy cellular function. Clean fasting can also reduce blood sugar levels and improve insulin resistance.

Are there risks to dirty fasting?

Given that there is still little research available on dirty fasting, it's hard to say if it has the same benefits as clean fasting, scientifically speaking. But if you want to ease your way into fasting and aren't as worried about weight loss, you might try working with a registered dietician to figure out the most sustainable way to achieve your health goals. Dieticians understand more about the science behind dieting and can help you come up with a plan customized to your goals and needs.

However, dirty fasting may be dangerous for some. Research shows that fasting can have negative effects on hormone levels in women. It's also not recommended for those who have type 2 diabetes, are pregnant or breastfeeding, are on certain medications, or are over 65 years old.

It's important to keep in mind that fasting can also be harmful to those who experience eating disorders or disordered eating, which could also have an effect on children or those who look up to you. "Are you normalizing body dissatisfaction or disordered eating?" asked registered dietitian Samantha Cassetty via EatingWell. "It's important to model a healthy relationship with food and your body, even if you aren't 100% happy with your body size or shape." Healthline suggests that the most effective way to maintain optimal health is through methods supported by science, such as eating a healthy diet, getting adequate sleep, and engaging in regular exercise.