Myths about Intermittent Fasting

There are a lot of talks lately about intermittent fasting as a way to lose weight and diet. This procedure requires abstaining totally or partially from eating for a specific time. Despite its popularity with an upward trend, its opponents often frown upon intermittent fasting due to some persisting myths associated with it.

This article intends to expose the prevailing myths about intermittent fasting to help you know the reality.

We recommend you rely on recent research rather than refusing to change your mind based on previous assumptions.

Today, the evidence in favour of intermittent fasting is much more substantial. Quality human studies, including systematic reviews at the top of the scientific studies hierarchy, support its benefits. However, myths about intermittent fasting persist. The goal here is to expose those weird myths.

Let's discuss them one by one in the light of scientific evidence. 


Intermittent Fasting: Myths vs Reality

Myth 1: It Slows Down Your Metabolism

A popular idea that supports this myth is that eating more often has metabolic benefits and that you should eat that way to lose more weight. This is what drives people to eat six meals a day. People have been obsessed with this idea of frequent eating recently and would eat their meals at regular intervals, whether at work or home, along with a protein shaker and six carefully counted almonds.

The argument behind it is that frequent eating speeds up metabolism based on the thermal effect of food and that eating causes a slight increase in metabolism.

In addition, the idea that intermittent fasting slows down metabolism originated as a result of an experimental study conducted with mice. But, it had two limitations:

  • Since mice have a short life span, a one-day fast would be equivalent to more than a week for them.
  • Mice are more sensitive to caloric deficits since they have very little fat. On the contrary, humans are the primates with one of the highest % of fat.

As far as frequent eating is concerned, the thermal effect of food is related to the amount of food consumed during a meal.

In simple words, if you consume 2000 calories per day, the thermal effect would be 200 calories. For example, the thermal effect of 6 meals of 333 calories each would be 33.3 calories or 200 in total. What if you consume three meals of 666 calories each? You burn ~ 66 per meal. Again, the total will be 200. 

As for the slowing down of metabolism by intermittent fasting, it is quite the opposite in humans. Fasting causes a slight increase in metabolism due to the increase in the release of orexin, which increases metabolic rate.

What slows down the metabolism is precisely a prolonged hypocaloric diet that causes a change in Leptin. But, it is already 3-4 days before the brain notices that change and the hypothalamus reacts.

Myth Busted: Thus, intermittent fasting does not slow down your metabolism rate. 

Myth 2: You Burn Muscles

This myth is supported by the idea that when your body consumes all the amino acids in the blood and stored glycogen, it begins to use the protein stores, your muscles, to convert them into glucose through a process called. That's why people are afraid of losing muscle by leaving too much time between meals.

However, this happens only during prolonged fasting. In fact, a recent systematic review confirms the results of many studies that prove that intermittent fasting, if done correctly, reduces fat mass and maintains muscle mass in humans. One possible limitation of these studies is that they are done in overweight people, and we know that fat protects muscle.

What would happen in people with a lot of muscle and little fat? 

Myth Busted: Another study conducted with Muslim bodybuilders confirms that fasting does not lead to loss of muscle mass and body composition. Thus, you do not lose muscle mass with intermittent fasting.

Muscle Anatomy

Myth 3: It Drops Sugar levels

The body is designed to maintain the proper glucose level in the blood, so it is not necessary to eat constantly. When we eat, we produce insulin to store excess glucose. When we fast, we produce glucagon and cortisol, responsible for using stored glucose and providing energy to the body. 

Myth Busted: Studies have determined that intermittent fasting helps regain sensitivity to a greater extent than classic calorie restriction in people with insulin resistance. However, there are no specific studies regarding the effects of intermittent fasting on people with hypoglycemia.

Myth 4: It Negatively Influences Sports Performance

The impact of fasting on performance depends on many factors, such as the individual's health status, correct protein intake, the type of physical activity, the fasting duration, and the adaptation level.

Myth Busted: An intermittent fasting approach with a sufficient intake of calories from good quality food sources and fluids could enhance physical performance. The truth is that training on an empty stomach favours adaptations.

An athlete running

Myth 5: It Leads to Hunger and Irritation

It is possible that this happens, especially when you do it the first time. Change is always difficult initially; it is a matter of adaptation. But, a lot of evidence suggests that increasing the frequency of meals increases hunger. The most important thing to improve adherence is to stay satisfied when you eat. For example, if you take 1,800 calories a day and divide them into six intakes, you have a 300 calorie meal. The result is constant hunger. 

Myth Busted: Regarding irritation, it is subjective. But some studies show that intermittent fasting improves mood states and depression symptoms. In addition, studies also suggest that reducing the frequency of meals reduces appetite.


Contrary to popular beliefs, intermittent fasting is a very beneficial tool for health if done correctly. That's why knowing what it brings us is necessary to banish the false beliefs associated with it and thus take advantage of this practice. We hope this article has helped you clear the doubts surrounding intermittent fasting and give this form of eating a try.


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