Fasting: What Does It Do To Your Body?

Fasting: What Does It Do To Your Body?

Fasting is a bit of a buzzword in the fitness industry at the moment.  

Suggested to improve almost all facets of health, fasting has become a very popular way to make large health changes by altering how you eat, rather than what you eat.

Fasting describes periods of normal eating that are then broken up by prolonged periods of fasting, with fasting being a period of time where you don’t eat at all.  

Popular Ways to Do Fasting

If we build on this notion a little further, fasting can be separated into a number of different styles, each of which is implemented very differently.  These are:

Time Restricted Feeding

Time restricted feeding is a type of fasting where you rotate between periods of eating and fasting within a single day.  

The most common application of time restricted feeding is the ‘leangains method’, which requires an 8-hour eating “window” and a 16-hour fast each day.

Alternate Day Fasting

Alternate day fasting describes a fasting style where you either avoid eating anything or you limit your energy intake to 500-6000 calories on set (non-consecutive) days of the week.  The most popular method of alternate day fasting is the 5:2 diet.

Learn More: The Truth Behind the 5:2 Diet

Periodic Fasting

Periodic fasting describes fasting periods that last multiple, consecutive days.  There are two types of periodic fasts: short-term periodic fasts (STPF) and long-term periodic fasts (LTPF).

A short-term periodic fast lasts less than three days.  A long-term periodic fast lasts longer than three consecutive days.

So, at this point, you might find yourself wondering: “What’s the point of fasting, whichever way I do it?”  And I get it. Simply ‘not eating’ doesn’t sound all that pleasant the first time you hear about it. But I can assure you that it’s nowhere near as bad as you think.

And it comes with a host of amazing health benefits.

The Health Benefits of Fasting

The health benefits of fasting are extremely wide-reaching, impacting your body in a startling number of ways.

Weight Management

By far the most talked about benefit of fasting is its ability to promote weight loss – something that has been shown time and time again.

You see, when you start fasting regularly (particularly on either a time restricted feeding or alternate day fasting schedule), you significantly reduce your daily energy intake (assuming you make an attempt to eat normally during your eating windows).  And consuming less energy is one of the simplest ways to lose weight.

Interestingly, unlike other traditional diet methods, fasting doesn’t appear to slow down your metabolism.  You burn just as many calories at rest as you did before you started losing weight!

So, considering these two points, it becomes pretty apparent why fasting is such a great tool for weight management: it helps you limit your daily energy intake without impacting your metabolism.

Reducing Body Fat

In addition to assisting weight management, fasting can have a huge impact on human growth hormone (HGH) secretion.  Some studies show that HGH can increase by up to about 5 times that of normal resting levels during fasting!  

If we take a second to consider that human growth hormone plays a key role in promoting the breakdown of fats for energy, it becomes pretty apparent how fasting can help promote fat-specific weight loss and improve body composition!  It lets extra HGH breakdown and metabolize stored fat!

Reducing the Risk of Type 2 Diabetes

When we eat carbohydrate-rich foods, they are immediately absorbed into the body, causing a rapid in blood sugar.  

This spike stimulates the secretion of the hormone insulin (also known as the ‘energy storage hormone’).  Insulin promotes the movement of sugar from the bloodstream into the body’s cells, where it can be used for energy.


Now, while this is all well and good under normal circumstances, if our diet is rich in processed carbohydrates (like the traditional Western diet, for example…) we can see chronically elevated blood sugar levels.  

This results in extreme insulin secretion, which can cause your body to become insulin resistant!

This creates a vicious cycle where both blood sugar and insulin secretion remain elevated all the time.  The combination of these factors wreaks absolute havoc with your body. It can cause a massive decline in metabolic health and an increase in the risk of developing type II diabetes.

Amazingly, fasting may be able to reduce resting blood sugar levels and insulin resistance.  As a result, it can greatly reduce your risk of developing diabetes and cause huge improvements in your metabolic health.

Protecting Your Arteries and Heart

Combined with its positive impact on metabolic health, fasting may have a positive effect on cardiovascular health – more specifically, on the health of your veins and arteries.

While this research is in its early stages, fasting appears to reduce the levels of specific fat molecules in your blood.  These happen to be the same fat molecules that can buildup in the walls of your blood vessels, causing atherosclerosis.  

With this in mind, researchers suspect fasting may be able to cause a significant improvement in cardiovascular health, while also reducing your risk of developing heart disease in a pretty big way.

Protecting Your Gut Health

Now, while this area of research is new, there is some evidence suggesting fasting can enhance gut health and function.  

Firstly, in mouse-based research, a 24-hour fast has been shown to cause significant increases in the development of intestinal stem cells.  This can significantly improve intestinal cell health, quality and function.

Secondly, mice who were placed on an intermittent fasting schedule during times of very high energy consumption (they were essentially force-fed sugar!) maintained a healthy balance of gut bacteria.  Mice who ate the same diet without fasting saw huge declines in gut bacterial health.

If we combine these two key research pieces with evidence demonstrating that obese and overweight individuals have significantly different bacterial profiles than their healthy weight counterparts, it suggests that fasting can enhance gastrointestinal health by enhancing weight loss, improving the state of your gut bacteria and increasing the health of your gut wall.

Protecting Your Brain

It might be hard to believe, but fasting may also protect your brain from age-related declines in cognitive function – and this comes down to a little process known as autophagy.

Autophagy describes the process whereby the body breaks down and destroys its own damaged or redundant cells.  

While this may not sound like a positive thing, it is actually an extremely beneficial process because it removes low-functioning cells from the body.  

With this in mind, there is an abundance of research to suggest that accelerated autophagy can protect against the onset of neurodegenerative diseases and cognitive dysfunction.

Interestingly, fasting has been shown to stimulate autophagy within the body.  This speeds up the removal of damaged brain and nerve cells, ensuring cognitive health and function.  

As a result, fasting can protect that brain from age-related declines in cognition and neurodegenerative diseases, like Parkinson’s and Alzheimer’s.

You can read more about enhancing your cognition through diet here, but the key piece of information to remember is: fasting protects your brain.

Read Next: How to Improve Cognitive Function Through Diet

Slowing the Aging Process

Although we have spoken about how you can limit the negative effects of the aging process at length in these articles, this is still worth touching on briefly, here.

I just mentioned that fasting (through prolonged calorie restriction) can stimulate autophagy and protect your brain.  But what I didn’t mention is that autophagy has far reaching effects throughout the entire body, and not just in the brain. Prolonged fasting has been shown to promote cellular regeneration throughout the entire body, improving cardiovascular health, metabolic health and hormonal function.

Through these interactions, fasting literally has the potential to stave off age-related declines in health everywhere in your body, allowing you to live a longer, and healthier, life.

Take Home Message

It looks like fasting is here to stay.  With recent evidence to suggest that it can impact nearly all aspects of health in a positive manner.  From enhancing weight loss to staving off age-related declines in cognitive and physical function, fasting can help you stay healthy. 

Whether you want to try ‘time restricted feeding’ or jump right into a ‘long-term periodic fast’, the choice is yours!  In either case, though, you can expect to see some serious health benefits!

Want to learn more about the practicalities of fasting?  Read our article: Intermittent Fasting Schedule and Rules [Infographic]

And if you would like other great information on health and diet,  make sure to follow us on Instagram


  1. This is a very informative. This will aid in my struggles with my health. I have been suffering from chronic bloating. Do you have any information on how to ease bloating? Thank you!

    • Hi Jen!

      Thank you for your kinds words. To answer your question, we will actually be releasing an article next week on foods to fight bloating. We hope to hear from you soon!


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