intermittent fasting vs calorie restriction

7 Reasons to Intermittent fast over calorie restriction

Last updated on October 23rd, 2020 at 09:08 pm


Global Weight Loss and Weight Management Market is accounted for $168.95 billion in 2016 and predicted to reach $278.95 billion by 2023 (1) with a CAGR of 7.4%. It’s clear that the world is obsessed with weight loss and the main cause behind the growth of the weight management industry is the growing number of bariatric surgeries and the rising number of lifestyle illnesses. 

There are two common approaches to effectively bring down bodyweight. 

Although most of the fitness trainers are always inclined towards a calorically restricted diet for weight loss several studies have proven the effectiveness of intermittent fasting over caloric restricted diet.

How does intermittent fasting prove better than a calorie-restricted diet? While the low-calorie diet has been known to have a negative impact on metabolic rate, fasting has been proven to leave metabolism unaffected. Intermittent fasting has been known to boost production of growth hormones that not only improves performance and strength but also protect your muscle from catabolization while fasting period. Choosing to fast over a low-calorie diet will be easy to follow weight loss protocol that also promotes autophagy.

let’s understand be basics before we discuss intermittent fasting vs calorie restriction diet patterns. 

Basics about caloric restriction diet?

For years, the calorie-restricted diet has been considered the best way to drop weight in a healthy way. 

Calorie restriction is an eating habit when you reduce your food intake without pushing your body into starvation mode. 

To follow the diet, the person needs to calculate his/her body’s daily caloric requirements and then design a daily diet that contains fewer calories than the required calories by body.

Feeding fewer calories than daily requirements initiate weight loss. 

Although, this diet pattern has been proven for its efficiency but some of its drawbacks were hard to ignore. we are going to discuss the drawbacks in the latter part of this article.

What is Intermittent Fasting?

Intermittent fasting is not a diet, it’s a lifestyle.

For many centuries, fasting has always been an integral part of many ancient civilizations, but it got its worldwide recognition in recent years. 

Muslims and Hindus were practicing fasting for thousands of years but that was followed because of religious beliefs. 

Now fasting has been scientifically proven (2, 3, 4, 5) to have multiple benefits and that’s the reason people belonging to different faith have incorporated fasting in their lifestyle.  

Intermittent fasting is a food pattern when you fast for a particular duration of time and then you are allowed to eat in a particular eating window. There are different forms of intermittent fasting, some of the most common forms are: 

  • 16:8 fasting- Conventional fasting
  • 20:4 fasting- also known as Warrior fasting
  • 24 hours fasting- OMAD (One meal a day)

In 16:8 fasting, you are allowed to eat in the 8-hour window and fast for 16 hours. In 20:4 fasting you shrink your fasting window to just 4 hours. 

One meal a day is my personal favorite to rip the full benefits of fasting. OMAD meal includes only a single meal in a day.  


Intermittent fasting vs Calorie restriction

Intermittent fasting and calorie-restricted diet are two different approaches to personal health, both have proven to be beneficial for improving body composition but both the diet pattern have different approaches to health. 

Let’s take a look at the key aspects where intermittent fasting surpasses the benefits of conventional caloric restricted diet pattern.

1# Long term sustainability

An optimum diet should be sustainable enough to help you experience the long term benefits. Let’s see how both the diet patterns fulfills the long term requirement of weight management. 

Calorie restriction: 

Secret of continuous fat loss is the improved Basal Metabolic Rate. 

Lack of long term sustainability is one of the biggest drawbacks of calorie-restricted diet. 

After a few months of eating in the calorie-restricted pattern, your body adapts to the low-calorie diet by reducing its own basal metabolic rate. 

How does it affect progress? Lowering down BMR (basal metabolic rate) leads to a reduction in the daily caloric requirement.  That means your body adapts itself to survive with low calories. 

With the low BMR, you gain weight at a faster pace once you get back to the normal eating pattern. 

In the 1950s Dr. Ancel Key’s famous Minnesota Starvation Study placed volunteers on a ‘semi-starvation’ diet of 1500 calories per day. In response to the restricted food volunteers, their basal metabolic rate dropped by about 30%. After the end of the restricted diet, volunteers were found to gain weight faster because of the low BMI. 

Another thing to worry about a calorie-restricted diet is the persistent low metabolism even after finishing diet (8).  

Intermittent fasting:

On the other hand, intermittent fasting has totally different results on the basal metabolic rate. 

Intermittent fasting doesn’t put your body on the “starvation mode”; instead, it places your body on a “fight or flight response mode”. 

Intermittent fasting stimulates multiple neurological and hormonal adaptation to the situation. Adaptation includes the release of catecholamines, which include adrenaline and noradrenaline, it also triggers the production of growth hormone (GH) that spike up the metabolic rate of the body. 

Why metabolism increase while fasting? 

The answer lies in the adaptation of primal human beings. Primal humans (before we learned the art of farming) were primarily dependent on hunting and there were days when the availability of food was limited. 

Putting the body on the starvation mode while the unavailability of food could have lead to the mass extinction of the human race. So instead of putting our body on the “starvation mode”, unavailability of food leads to the body’s “fight response” to the situation. In simple terms, over a period of time, the human body adapted to the new pattern when it secreted all essential hormones to achieve top performance even in the absence of food.  

A study (6) conducted at the University of Vienna proved the point. Researchers found the accelerated fat loss by increasing the overall metabolic rate. 

In short, instead of putting the body on the “starvation mode”, intermittent fasting lead to the secretion of hormones that help in elevated metabolism for energy and higher performance. 

#2 Muscle Health

While some of the people are looking for accelerated weight reduction others are just looking to cut down on fat while preserving muscle mass. Let’s have a look how body diet patterns respond.

Calorie restricted diet

Diet with a calorie restriction not only reduces your metabolic rate but it also leads to the loss in muscle mass. 

Numerous studies (9, 10) have proven the negative effects of a calorie-restricted diet on muscle mass if the optimum ratio of protein is not included in the diet.  

Basically, a calorie-restricted diet is too complicated to be designed by yourself, to get good weight loss results you will be required to take expert advice to reach the desired body composition goal. 

Intermittent fasting

Intermittent fasting has been proven superior to maintain and develop muscle mass.  

Fasting has been proven to naturally increase the production of growth hormones. A study  (11) conducted on “effect of prolonged fasting on levels of growth hormone-binding protein and free growth hormone” researchers found a considerable increase in GH after 24 hours fast. Other studies (12, 13) conducted on the effects of different types of fasting on growth hormone production found similar improvement in the production of GH, some studies observed the improvement of up to 300% in growth hormone production. 

The human growth hormone is a hormone that has many health benefits, including – growth, metabolism, strength gains and weight loss. 

Production of Human Growth Hormones (HGH) led to the promotion of fat burning while preserving muscle tissues. The growth hormone is a leading factor that determines maximum fat burning and preserving muscle mass at the same time. 


3# Testosterone levels

Apart from growth hormone, another hormone that plays an influential role in a healthy body is the “Testosterone levels”

Testosterone is a powerful male hormone, which is responsible for major functions in the male body, like sex drive, muscle building capacity, bone density, mood swings, etc.

Let’s see how both diet patterns affect your testosterone levels- 

Calorie restriction diet: 

In the pursuit to lose weight fast, watch out if you are losing your testosterone levels because of calorie restriction. 

A study (14) conducted on the effects of a calorie-restricted diet in Amateur Wrestlers and Its Effect on Serum Testosterone Levels found some eye-opening results. Researchers concluded, “Large reductions in body fat induced by caloric restriction and exercise during the season resulted in the largest decreases in testosterone.”

Another study conducted on the group of soldiers who were given low (1800 kcal/day), moderate (3200 kcal/day), or high (4200 kcal/day) calorie diets. After 5 days of dieting and sleep deprivation lead to the drop in testosterone levels to 50%.  

Intermittent fasting

Fasting has been proven very effective in maintaining healthy levels of testosterone levels. 

A study conducted on the effects of short term fasting with a group of non-obese men. It found some promising results, the study stated LH (luteinizing hormone – a testosterone precursor hormone) rises up to 67% and overall testosterone increased by 180%.

So basically, a simple 16 hours fasting can help you retain your muscle mass and keep your body healthy. 

A study conducted at the Department of Internal Medicine, University of Virginia Medical School, Charlottesville found breathtaking improvement in GH production. Researchers found, just a 24-hour fast can elevate your growth hormone levels by up to 2000% in men.


4# Autophagy

Autophagy is the body’s natural mechanism to regulate the elimination of cells that are unnecessary or dysfunctional. It allows the orderly degradation and recycling of cellular components. 

Autophagy has become more essential because of the increment in environmental pollution. Toxins have become a part of our life, they are in the air we breathe in, the water we drink and the food we eat, and these toxins are making us vulnerable to life-threatening diseases (like cancer). Let’s see how these diets affect the natural process of autophagy. 

Calorie restricted diet on autophagy

Calorie restricted diet has always been linked to the anti-aging because of its ability to promote autophagy. To a greater extent, a calorie-restricted diet is far better than a regular diet for cellular level repair and regeneration. 

Intermittent fasting on autophagy

When it comes to autophagy, fasting has left calorie-restricted way behind. 

The promotion of autophagy has been one of the greatest benefits of intermittent fasting. Fasting is a very powerful tool to treat and prevent tumor formation, one 2002 study (15) on rat found that alternate-day fasting helped block tumor formation. 

Another test-tube study (16) found that several cycles of fasting were found to be as effective as chemotherapy to delay the growth of the tumor. 

Although there is still an absence of concrete evidence proving the effectiveness of fasting in reducing the effects of tumors. 

Autophagy is directly related to insulin levels, the rate of autophagy is low in a few states because of the abundance of insulin. Insulin drops while fasted state which can help in promoting the process of autophagy for up to 5-folds. 

The size of your fasting window decides the level of autophagy your body experiences. By increasing autophagy, intermittent fasting causes the breakdown and clearance of damaged cell parts.

5# Financial aspect

 The financial aspect is a significant factor, no one wants to spend unnecessary bucks (some exceptions are always there). I have also seen many people who were unable to follow a diet given by dieticians because of monetary aspect, not everyone is capable of spending hundreds of bucks on supplementations required for accelerated fat loss.

Calorie restriction diet: 

A calorie restriction diet may demand you to consume a 4-6 low calories diet. 

It’s not always feasible to prepare all meals at home which results in buying yourself food from the stores or cafeterias. Basically, a calorie-restricted might add-up financial burden on you.

Intermittent fasting

Intermittent fasting not just assist in transforming into a healthier being but it also helps in saving a lot of money. 

16-hours of fasting allows you to skip breakfast which definitely helps in saving a few bucks. 24-hours fasting saves a lot of time and money on unnecessary snacking. 

Eating all day is unhealthy and expensive too. Following One meal a day is an inexpensive way to stay lean all season. 

6# Mental clarity/ Energy levels

Everyone wants to lose weight but not at the cost of low mental clarity or energy levels. 

Maintaining good energy levels is an important aspect of efficient diet. Let’s see the difference in energy levels of both tiet.. 

Calorie restricted diet on energy levels

Calorie restricted diet is designed to feed fewer calories than the daily caloric requirement that can lead to low mental clarity for most people. 

Additionally, restricted diet is also proven to slow down the basal metabolic rate that surely have an adverse effect on the energy levels. 

Intermittent fasting on energy levels

Fasting, on the other hand, is quite difficult to start and many people are not even strong enough to survive it for a few weeks. 

Starting intermittent fasting can surely make you feel dizzy and jittery in the beginning but soon your body will adapt to new diet patterns. 

Once you adapt to fasting, you will feel way more energetic and awake. Fasting helps in boosting the metabolic rate of the body that helps in improved energy levels. Plus, fasting also promotes the production of ketones, these are the chemicals made in the liver who help in breaking down stored fat to energy which results in an alternative source of energy for better mental clarity. 

Additionally, fasting also affects testosterone levels, a 16 hours fasting can help in doubling up the T-hormone and 24 hours fasting can elevate is up to multiple folds. Do I need to say it again that testosterone is a hormone that helps you with better mood, libido, energy, metabolism, etc? 


7# Fighting other health issues

There is no bro-science behind the people’s beliefs over fasting. Several studies have proven the effectiveness of fasting in reducing the risk of diabetes, cardiovascular disease and certain types of cancer. 

8# Spiritual benefits

Are you someone who is looking to improve the discipline and willpower? Triumph over hunger should be your first target then. 

Fasting has been used by ancient yogis as a pathway to spirituality. If you ever go to India in search of the purpose of life or spirituality then the first thing  your guru will train you for is ‘fasting’. 


Thanks for reading. Questions welcomed in the comments as always. 

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