Intermittent fasting is currently a very popular method to lose weight and improve health.

In addition to being Google’s hottest trending dietary search in 2019, its health benefits were also prominently featured in an authoritative review study by the New England Journal of Medicine (NEJM)–arguably the most prestigious medical journal (1).

There’s mounting evidence that intermittent fasting could be a potential cure for many chronic health conditions, including insulin resistance, heart disease, and even cancer. That’s exciting news.

So, if you’re now curious about intermittent fasting–what it is, its specific health-promoting benefits, and how you can get started on it, read on.

This article covers everything you need to know about intermittent fasting. 

What is Intermittent Fasting?

Intermittent fasting, also known as cyclic fasting, is as its name suggests: cycling between periods of fasting and eating.

As there are no restrictions on the types or amounts of food that a person can eat during the eating window, intermittent fasting is not a diet per se. Instead, it’s classified as a pattern of eating (2). And this flexibility makes intermittent fasting relatively easy to follow.

You might be surprised by this, but intermittent fasting is nothing new.

The term ‘intermittent fasting’ itself is, but humans’ practice of fasting–for religious, social, cultural, or political reasons–dates back thousands of years in a variety of societies and civilisations. In fact, it still plays a central role in many major religions today.

For example, once a year, Muslims observe Ramadan, a month of fasting from dawn until sunset.

Why Intermittent Fast?

With food readily available 24/7, why intermittent fast?

Because of the metabolic shift that occurs when you stop burning glucose for fuel after your glucose and glycogen stores have been depleted and instead burn fatty acids when you go without food for extended periods (i.e. fasting) (3, 4, 5). 

As a result of this metabolic switching, an age-old adaptation to periods of food scarcity, your body starts to produce ketone bodies which are not just fuel used during periods of fasting but are also potent signalling molecules with major effects on cell and organ functions.

For example, during fasting, your cells activate pathways that enhance intrinsic defences against oxidative and metabolic stress and those that remove or repair damaged molecules. Meaning your body is slowly reinforced against cellular stress and is then less susceptible to cellular ageing and disease development.

Here are more changes that occur in your body as a result of metabolic switching:

• Increased levels of Human Growth Hormone (HGH) – The levels of growth hormone in your body increases by as much as 5-fold. This, in turn, brings about other health benefits, including fat loss, muscle gain, and bone health (6, 7, 8).

• Improved insulin sensitivity – Due to improved insulin sensitivity, the levels of insulin in your body decreases. And with that, your body is better able to access and burn stored fat (9).

• Cellular repair – The production of ketone bodies when you're in a fasted state allows you to tap into autophagy, a cellular remodelling and regenerative process where cells digest and remove the build-up of old and dysfunction proteins within cells (10, 11).

• Gene expression – Fasting leads to changes in the functions of genes related to longevity and protection against disease (12, 13).

  
  

And it is precisely these cellular and molecular changes that occur within the body that leads to the variety of health benefits related to intermittent fasting.

Benefits of Intermittent Fasting

Weight loss

One of the major benefits intermittent fasting provides is weight loss. Because of the restriction on the number of hours you can eat over the day, you’ll naturally eat fewer meals.

And that leads to an automatic reduction in calorie intake without the need for you to meticulously track every calorie you’re consuming. Also, it appears that the reason why intermittent fasting promotes weight loss goes beyond a calorie reduction.

As mentioned earlier, when you fast, your body switches its source of fuel from glucose to fat.

And that means your body starts breaking down your fat stores, which were previously inaccessible when you were constantly eating (i.e. not fasting). Additionally, intermittent fasting increases your body’s release of the hormone norepinephrine, which has been identified to trigger fat-burning in the gut (14).

Due to the combination of the above factors, intermittent fasting has been heralded as a potent weight-loss tool. And research supports it.

A randomised clinical trial of obese adults indicated that intermittent fasting was just as effective as standard calorie restriction at producing weight loss effects, according to a 2017 paper published in JAMA Internal Medicine (15).

More compelling evidence comes from a 2018 pilot study published in the Journal of Nutrition and Healthy Eating: it suggested that intermittent fasting can help obese dieters lose weight without having to count every single calorie they eat (16).

Of course, these findings may surprise you.

You’d think that after abstaining from food, people would compensate during the feeding window by eating like they were at an all-you-can-eat buffet, essentially negating the calorie-deficit.

Interestingly, there appears to be a ceiling to overeating. According to a 2016 study, participants only ate around 10 to 22% extra during their feeding windows and, thus, managed to incur an overall caloric reduction of around 28% over the week (17).

Reduced Insulin Resistance

Insulin resistance happens when your body can’t properly use the hormone insulin to regulate your blood glucose (i.e. sugar) levels.

Worryingly, insulin resistance can lead to excessively high blood sugar, which paves the way for type 2 diabetes (18, 19). As you can imagine, anything that reduces insulin resistance, should, therefore, help lower blood sugar levels and protect you against type 2 diabetes. And that’s intermittent fasting.

A 2014 study in the journal Translational Research found that intermittent fasting resulted in clinically significant reductions in blood sugar and insulin resistance amongst participants (20).

One promising study in diabetic rats also showed that cycling between fasted and fed states protected against one of the most severe complications of diabetes: kidney damage (21).

That said, it’s important to note that intermittent fasting shouldn’t be used as a replacement for prescribed medications meant to treat or manage diabetes.

Lowered Oxidative Stress and Inflammation

If you’ve stumbled upon advertisements for the latest trending skincare products, chances are, you would have heard of the term ‘oxidative stress.’

But here’s something you should know. Oxidative stress doesn’t only affect your skin but every cell in your body. To put it simply, oxidative stress occurs when there are more free radicals than antioxidants present in your body.

Because of free radicals’ highly unstable state, they can cause large chain chemical reactions in your body–in turn, causing damage to fatty tissue, DNA, and proteins in your body (22, 23, 24).

Thankfully, several studies show that intermittent fasting may enhance the body’s resistance to oxidative stress (25, 26).

Due to the link between oxidative stress and inflammation, several studies also show that intermittent fasting can help fight inflammation–another key driver to all sorts of common chronic health conditions, including rheumatoid arthritis, cancer, asthma, and even Alzheimer’s (27, 28, 29).

Decreased Risk of Heart Disease

Heart disease is currently the world’s biggest killer (30).

And as you’re probably already aware, many forms of heart disease can be prevented or treated with healthy lifestyle choices–one of which is intermittent fasting.

Research indicates that intermittent fasting has been shown to improve numerous risk factors–including blood pressure, total and LDL cholesterol, blood triglycerides, inflammatory markers, and blood sugar levels–for heart disease (31, 32, 33).

More specifically, a 2012 study showed that fasting increased good HDL cholesterol and decreased both bad LDL cholesterol and triglyceride levels (34).

A 2010 animal study published in the Journal of Nutritional Biochemistry also showed that intermittent fasting caused an increase in levels of adiponectin–a protein involved in the metabolism of fat and sugar that may be protective against heart disease (35, 36).

How to Get Started on Intermittent Fasting

Before you proceed to skip your next meal, bear in mind that there are a couple of different approaches to intermittent fasting, with 3 of the most popular ways below:

• 16/8 – Involves fasting for 14 to 16 hours and restricting your daily eating window to 8 to 10 hours.

• 5:2 – Involves eating normally (aka as you would) 5 days of the week while restricting your calorie intake to just 500 to 600 calories for 2 days of the week. These 2 days of fasting need not be consecutive.

• Alternate day fasting – As its naming convention suggests, this is where you fast every other day. Note that there are several different versions of this method; some of them allow about 500 calories during fasting days, which is a much less extreme version than a full fast every other day (recommended for beginners).

  
  

While there is no ‘best’ intermittent fasting, the 16:8 method is arguably the easiest to get started on and stick to in the long-term. That's because doing this method can be as simple as not anything after dinner and skipping breakfast.

For example, you could have your last meal for the day at 8 pm, then only eat at noon the next day–and that means you’ve technically already fasted for 16 hours.

For what it's worth, this simple switch in your eating pattern is incredibly easy to do. And when paired with the mounting evidence of the health benefits it can provide, it can be difficult to think of a reason not to try it.