"Dirty" vs. "Clean" fasting... what's the difference and is one better at burning fat than the other? Today, we're diving into the details on dirty vs. clean fasting and what type of fasting is best for your weight loss goals.
What is "Dirty Fasting"?
"Dirty" fasting is a newer term describing a type of Intermittent Fast where you're allowed to have certain foods and not break your fast. There are a few ways to approach "dirty" fasting:
From a calorie perspective
From an insulin perspective
From a calorie perspective, proponents of this type of "dirty" fasting will suggest that anything less than 100 calories will not break a fast. This approach isn't discriminatory against the types of calories consumed. This means anything from fat to protein to sugar is fair game.
From my experience as a Nutritionist, this perspective of dirty fasting doesn't make much physiological sense. 100 calories of fat has a much different impact on the body than 100 calories of carbs. Adding 100 calories of sugar to your morning coffee will spike your storing hormone insulin and shift you out of any debatable state of fasting.
Which brings us to the second "dirty fasting" theory:
From an insulin perspective, anything that doesn't cause the fat storing hormone insulin to spike can be had during a fasted state. Pure fat is the only macronutrient that does not cause insulin to spike. This means that following this protocol allows you to consume any pure fat source such as grass-fed butter, coconut oil and MCT oil.
The rationale behind this theory is specifically related to weight loss and blood sugar concerns. One of the main benefits of Intermittent Fasting is that it allows for a natural dip in the storing hormone insulin, and therefore makes it easier for the body to utilize fat as fuel and achieve a weight loss goal.(1) Following this logic, since fat does not cause an insulin response, fat during the fast will not "break" the fast.
This is why many people are consuming pure fat coffee and tea drinks during their fasted state and still seeing great weight loss and fat burning results.
What is "Clean Fasting"?
Clean fasting involves not consuming any calorie containing foods or beverages during your fast. This involves sticking to water, unsweetened tea and unsweetened coffee. In some cases, "clean fasting" proponents will suggest that you can only have water during your fasted state.
"Clean" fasting maintains the benefits of naturally lower insulin levels and therefore boosted fat burning that the second "dirty fasting" option has.(1) However, "clean" fasting has the added perk of boosting the gut healing process called the Migrating Motor Complex. This natural process involves a series of contractions and secretions in the GI Tract that prevents bloating in the body and is only triggered when you haven't had anything to eat or drink (other than water) for at least 3 hours and 45 minutes.(2)