5 Fasting Facts Backed By Science

Weight Loss & Diets | Written by Nathan | Updated on 27 July 2022

A notebook for someone to write down their diet plan and fasting facts for a healthy weight loss journey.

Understanding important fasting facts backed by science is essential to fully understanding how to incorporate fading into your life. By researching the role calories play in weight loss, hunger vs. thirst, exercising, how fasting can help with stress and mental health, and the importance of protein, you can safely begin fasting. 

Fasting Fact # 1 – Calories In, Calories-Out (CICO) is King

With plenty of new rules and fad diets, we may wonder whether calories in vs. calories expended really matters concerning weight gain or weight loss? In short, the answer is yes – the calories in vs. calories is king and is the most important thing regarding weight loss. Beginners fasting should remember the principles of CICO above all other fasting myths that are bound to be seen online.  

“Calories in”, or calories that a person consumes, is the energy/calories they obtain via eating and drinking. There are calories in almost any food and liquid that we eat or drink, which will increase with what we intake throughout the day.

“Calories out” refers to the expenditure and the energy that we are burning. Our body needs energy to perform basic functions to keep us alive, such as digestion, blood flow, breathing, powering our brain, and much more. The amount of energy needed to sustain our bodily functions is called the basal metabolic rate – without enough energy, our body would soon shut down. 

Not only do we burn calories performing basic bodily functions, but we also move our body throughout the day. When combining the basal metabolic rate and physical activity, we can determine the required number of calories to lose weight, maintain, or gain weight. 

In relation to the CICO diet, fasting is slightly different from simply reducing your calorie intake vs. expenditure. Studies have shown that when comparing a calorie restriction vs. intermittent fasting diets, the latter is more effective in long-term health benefits, longer lifespan, and reduced occurrence of cancer [1]. 

Instead of solely restricting calories to drop pounds – facilitated by an unhealthy narrative – you can schedule your fasting periods to begin dieting safely.

Fasting Fact # 2 – Hunger Pangs Are Often Mistaken for Thirst

One of the most important nutrients that we can consume on a daily basis is something that people often forget about – water. Instead of giving in to temptation and feeding yourself with empty calories that do not contain any nutrients – and giving into hunger pangs that are actually the sensation of thirst – we are simply playing our body with unneeded sugars and fats. Though it is often forgotten about, drinking water is one of the easiest fasting facts to follow.

Drinking water throughout the day is one of the best ways to have healthy digestion, circulation of nutrients throughout your body, and facilitate a higher chance at weight loss. Water is essential during fasting – there are some cases in which drinking liquids of any type are not allowed during a fast, such as for religious purposes. 

However, for those doing intermittent fasting for only health reasons, drinking water helps you stay hydrated and does not negatively affect blood sugar or insulin levels during the fast [2]. 

In some cases, especially when you are on a severely restricted calorie diet or during fasting, you may feel hunger pangs more often than “normal”. Studies have shown that people often feel the sensation of hunger due to motivational instances and psychological cravings for the sensation of food – but these cravings can typically be satisfied by drinking water [3]. It is also very common for thirst to be confused with hunger [4]. Therefore, feeling hungry can be quickly remedied by drinking water during intermittent fasting

Fasting Fact # 3 – Exercising While Fasting Isn’t Dangerous

During a fast, it can be hard to maintain your energy levels and a balanced level of physical activity. However, exercising during fasting isn’t dangerous if done right, it can actually be a great way to positively influence your hormone levels, reduce cravings for high-calorie foods, and mentally detract from the need to think or eat food. As a helpful weight loss solution, exercise positively affects almost everyone, helping individuals reduce their calorie intake and feel positive about themselves throughout the day [4]. 

But how can you safely exercise during fasting? A few things that will help your consistency when it comes to exercise includes thinking about the timing of your workout, selecting the right type of intensity based on your energy intake, and eating healthily before or after the workout to get the desired effects of the workout (building muscle or losing fat) [5]. 

  • Timing – Figuring out when you have peak energy levels and when you prefer working out, such as on an empty stomach vs. right after a meal, can be helpful in scheduling your exercise.
  • Type of Workout – Depending on your macronutrient intake and your intermittent fasting schedule, you can choose the best workout to accommodate your diet. For example, you can correlate a low-carbohydrate day with a HIIT session for optimal results.
  • Eating After a Workout – The last tip to make exercise easy during intermittent fasting is to time foods after a workout based on the specific benefits you want to achieve, like slimming down or maintaining muscle. This can help replenish protein, glucose, and other nutrients to build muscle and/or lose weight.

Following these fasting facts will make it easier to exercise while intermittent fasting. The benefits of exercising while on a fast include the potential of managing blood sugar levels, burning extra fat during your workout, and keeping an eye on type 2 diabetes [5]. 

Fasting Fact # 4: Fasting Helps With Sleep, Stress, and Mental Health

In addition to helping with weight maintenance, fasting can help individuals prioritize sleep, deal with stress, and focus on positive mental health. Intermittent fasting can be one of the best diet rule strategies to help those who are suffering from affective disorders, sleep disorders, and cognitive disorders by changing the timing and frequency of brain signaling in those affected [6]. Furthermore, studies have shown positive effects on mental health, with results stating that fasting positively influenced the relation between insomnia, anxiety, and social dysfunction [7]. 

Fasting not only has positive effects for those with mental health concerns or cognitive disorders, but can signify those who have sleep disorders. Intermittent fasting can help those with sleep disturbances, reducing the likelihood of individuals waking up during the night, providing a more restful night’s sleep, and increasing the individual’s mood and focus during the following day [8]. 

Lastly, intermittent fasting is an efficient method of reducing stress. Studies have shown that intermittent fasting can help individuals prone to high levels of stress by regulating cortisol, the hormone associated with the body’s fight or flight in response to a stressful stimulus [9]. If done safely, this dieting trend can boost your weight loss goals. 

Fasting Fact # 5 – You Can Get Enough Protein While Fasting

Protein is one of the main macronutrients that we find in our diet. Without enough protein, our body would be unable to lose weight, gain muscle, and have enough energy for our daily activities. So how does one who is intermittent fasting get the required amount of protein to maintain muscle mass and facilitate weight loss?

Although getting the correct protein intake while fasting can be difficult, it is not impossible. Even though it may take more planning and meal prepping in advance, individuals who are intermittent fasting can still have the same amount of protein in their diet as they would regularly. If you are always on-the-go, you can drink protein shakes for weight loss and maximum results all while sticking to the above mentioned fasting facts. 


[1] Calorie Restriction and Fasting Diets: What do we Know? National Institute on Aging, 2018. 

[2] Rachael Link (2021). Can you drink water when fasting? Retrieved from https://www.healthline.com/nutrition/can-you-drink-water-when-fasting#intermittent-fasting

[3] Betley, J., Xu, S., Cao, Z. (2015). Neurons for hunger and thirst transmit a negative-valence teaching signal. Nature 521, 180–185. https://doi.org/10.1038/nature14416

[4] Synder, C. & Petre, A. (2021). 13 Science-Backed Ways to Help Reduce Hunger and Appetite. Retrieved from https://www.healthline.com/nutrition/ways-reduce-hunger-appetite#TOC_TITLE_HDR_6

[5] Daniel Bubnis. (2020). How to Exercise Safely During Intermittent Fasting. Retrieved from https://www.healthline.com/health/how-to-exercise-safely-intermittent-fasting#effective-workouts-while-fasting

[6] Currenti, W., Godos, J., Castellano, S., Mogavero, M., Ferri, R., Caraci, F., Grosso, G., & Galvano, F. (2021). Time restricted feeding and mental health: a review of possible mechanisms on affective and cognitive disorders. International Journal of Food Sciences and Nutrition, 72(6), 723-733, DOI: 10.1080/09637486.2020.1866504

[7] Seyed Ali, M., Mansour, R., Sahar, A., & Maryam, S. (2014). Effect of Fasting on Mental Health in the General Population of Kermanshah, Iran. Journal of Fasting and Health, 2(2), 65-70.

[8] Tom Ryan. (2021). Why Intermittent Fasting Can Lead to Better Sleep. Retrieved from https://www.sleepfoundation.org/physical-health/intermittent-fasting-sleep

[9] Natasha Adelayanti. (2020). Discovering the Advantages of Fasting For Mental Health. Retrieved from https://www.ugm.ac.id/en/news/19358-discovering-the-advantages-of-fasting-for-mental-health

About the Author


Nathan has been a fitness enthusiast for the past 12 years and jumps between several types of training such as bodybuilding, powerlifting, cycling, gymnastics, and backcountry hiking. Due to the varying caloric needs of numerous sports, he has cycled between all types of diets and currently eats a whole food diet. In addition, Nathan lives with several injuries such as hip impingement, spondylolisthesis, and scoliosis, so he underwent self-rehabilitation and no longer lives with debilitating pain.