What Does Intermittent Fasting Do to Your Body and What Are Its Benefits?

Heather Campbell
 min read

What does intermittent fasting do to your body and does it work?

What Does Intermittent Fasting Do to Your Body and What Are Its Benefits?Why do we eat all the time? Why do we think we should eat every two or three hours?

As a whole, intermittent fasting means that the body burns fat for energy, with steady blood sugar levels, improved fitness, accelerated fat loss, mental clarity, and it stimulates autophagy, improves gut microbiome, reduces sugar cravings and repairs defective mitochondria.

Our bodies benefit from fasting for a while instead of eating regularly.

Fasting is something different cultures have done for centuries, for religious or cultural reasons. We have fasted in all shapes and sizes. Read on to understand what does intermittent fasting do to your body.

What does intermittent fasting do to your body? Introduction

Fasting works so well because there is minimal insulin release. As a result, your insulin plummets at a rapid rate.

You make your own body more sensitive to insulin again by effectively reducing insulin resistance.

This doesn’t happen if you keep eating every day, even if it’s less.

Compare it to a bit of running: is running five miles once a week the same as running one mile five times a week?

The effect is totally different. This also applies to fasting.

Source: Halberg, et al., Effect of intermittent fasting and refeeding on insulin action in healthy men, Journal of Applied Physiology, 2005

What happens to our bodies while fasting

During fasting, you completely empty all the cells of your body for a while. Our cells get almost no chance to discharge waste products by eating and snacking all day long.

It all stays stored away in our cells. Our cells are bulging and can no longer function properly because there are leftover fats and proteins everywhere.

Our body has time to purge

What does intermittent fasting do to your body? We rid our bodies of old, damaged, or worn-out cells and structures in fasting. Our bodies can recycle some of these particles and make room for new, younger particles, called autophagy.

Fasting is like cleaning your home. You get everything out of the way, dust everything off, and air the place out.

When your home is a mess, you often become restless. Taking a moment to put away the dishes and vacuum your house will also clear your head and allow you to think and work.

So it is with the cells in our body. Space through fasting allows the cells to work better again.

When fasting, we use our reserves

After you eat a meal, your body will always burn the energy that came in with that meal first. Thus, the last meal is used as fuel.

But if you are fasting, there is no meal, and your body will use its reserves.

The blood sugar doesn’t plummet, and hypoglycemia doesn’t occur when fasting because the body:

  1. first burns glycogen, the supply of stored sugar in the muscles, and
  2. then proceeds to burn fat within 24 to 36 hours because there is no food or snack to provide us with sugar-rich energy.

So what does intermittent fasting do to your body? By fasting, you start burning your stored reserves and your stored fat, and you clean up and lose weight more quickly.

Strangely, we are not hungrier when fasting

The funny thing about fasting is that you actually get less hungry, contrary to what you might expect. For example, burning the body fat as energy gives a constant blood sugar level without peaks and valleys.

You’ll have fewer cravings for sugary snacks. The mitochondria in cells are the power plants that provide energy.

By burning more fat, the cell is stimulated to make better mitochondria, which burn more efficiently. Thus, fat is an ideal fuel for our cells, especially for long and sustainable burning.

So if you fast for longer than 24 hours, you switch from burning sugar to burning fat. That transition is more manageable if you already eat less sugar or less starch and more healthy fats and proteins.

Eleven benefits of periodic fasting

Fasting is not appropriate for everyone and is not recommended for pregnant women or want to become pregnant.

Always consult with a physician before fasting to determine if it is appropriate for you.

However, fasting has many unforeseen benefits.

The benefits are only there if you stay away from sugary or over-processed foods, foods high in fast carbohydrates, or junk food on your non-fasting days.

Here is a summary of some of the benefits of fasting in a row:

Fasting improves fitness

Exercising while fasting can have many positive effects on the body, including:

  • improved metabolic responses to post-workout meals, crucial for rapid recovery
  • stronger metabolic adaptations
  • higher sensitivity to growth factors (think muscle synthesis)

We are talking about healthy exercise here, not world-class athletic performance.

So, while training during fasting has a place, even among high-level athletes, it does not mean that it is optimal during all periods of the training or competition cycle.

Start very gradually and under professional guidance if you want to start doing this yourself.


Fasting accelerates fat loss

During fasting, you burn stored body fat as fuel. Consider the example of the camel. A camel uses water from its hump during fasting on a long dry desert journey.

Through fasting, we thus use fat from our own fat hump, which is the belly or buttocks for most of us.

A study done in 2017 looked at the effects of seven days of fasting (<300 kcal per day) in people with type 2 diabetes.

Fasting was sustained quite easily by all. Only after four months did they look at the results of that one week of fasting:

  • The fasting group had lost 7.7 pounds, while the control group who received standard diabetes care lost 4.4 pounds.
  • Abdominal circumference was also significantly improved.
  • This was also true for blood pressure.
  • In addition, quality of life was also improved.
  • Diabetes values had improved slightly, but not considerably.

The authors conclude that fasting is feasible and that more extended studies are needed to better understand the long-term effects.

A 2017 review article shows that 11 of 17 studies show that you can get significant weight loss with fasting.

However, the authors acknowledge that fasting has only recently received renewed attention in science and that more long-term studies are needed.


Fasting gives you mental clarity

So even though the brain needs glucose for energy, it can also get energy from breakdown products made by fat burning called ketones.

Ketones from fat are the most energy-efficient and high-energy fuel available to our bodies, making our brains especially happy.

The brain cells can burn ketones very efficiently, which is thought to be the reason for a feeling of clarity after fasting.

However, there is no consensus, as memory improvement may be due to an adrenergic response.

You get into the fight-or-flight response, and as a primal human, you have to be able to think clearly to hunt prey.

However, what is clear is that there are fewer sugar level fluctuations and less insulin release. This also keeps you from having an energy dip after eating.

Source: Cherif, et al., Effects of Intermittent Fasting, Caloric Restriction, and Ramadan Intermittent Fasting on Cognitive Performance at Rest and During Exercise in Adults, Sports Medicine, 2016

Fasting stimulates autophagy

Autophagy is essentially the way our bodies do housekeeping.

Many of our basic cellular processes create waste, which must either be excreted by our bodies or recycled to improve the efficiency and function of our various organelles.

Autophagy is part of that sorting process and is always ongoing but is given much more space during fasting.

Fasting improves glucose uptake and insulin sensitivity

Periodic fasting helps increase the glucose uptake rate in tissues such as muscles that can use it for fuel.

It also helps to lower and normalize insulin and glucose levels.

Source: Patterson & Sears, Metabolic Effects of Intermittent Fasting, Annual Review of Nutrition, 2017

Fasting improves your gut microbiome

Fasting appears to positively affect your microbiome because it deals with the overgrowth of certain one-sided bacterial colonies that are excessively present.

For example, this could be due to medication use or an unhealthy diet.

You can compare it to a gardener who removes bothersome weeds to encourage the growth of desirable flowers.

Fasting repairs defective mitochondria

Think of mitochondria as the power plants of your cells that inevitably suffer damage over time, making them less efficient at using fuel.

During fasting, ATP (energy) reserves decrease, and the body is stimulated to create more and better mitochondria.

This means that the moment food is available again, it will be burned more efficiently.

Fasting improves brain function

Fasting increases Brain-Derived Neurotrophic Factor (BDNF), also known as abrineurin, a protein involved in learning and memory.

BDNF helps us make certain brain pathways faster and more efficiently.


Fasting reduces oxidative stress and inflammation

Working constantly is pretty tough on our power plants, the mitochondria, creating an overly tense situation.

Many waste products or free radicals are made and not cleared in this stressful situation. Instead, we create peace in the cell and make our bodies more resilient by fasting.

This prevents the stress situation from getting out of control. For example, an overworked cell has a lot of free radicals and will lightly inflame.

Prolonged mild inflammation causes many Western diseases and has even been linked to diabetes.

Source: Faris, et al., Intermittent fasting during Ramadan attenuates proinflammatory cytokines and immune cells in healthy subjects, Nutrition Research, 2012

Fasting can improve diabetes treatment

Fasting lowers blood sugar levels in people with diabetes who are on medication, providing the opportunity to reduce drug use and improve diabetes treatment.

One study compared two groups of people who went on a fast. One group fasted two days in a row, and the other group had two fasting days spread throughout the week.

Both groups had lower blood sugar levels despite reducing medication. Also, both groups had improved HbA1c levels, fasting glucose, lost body weight, and improved quality of life.

Of course, the fact that fasting gives low blood sugar levels is good news since it actually means that diabetes medication could have been reduced even more drastically.

In other words, fasting can help reduce diabetes medication.


Fasting reduces your appetite

When you switch to burning fat (from fat storage in your body) instead of constantly burning sugars (from your meal), your body gets a stable energy supply.

When you depend on energy from sugar, you experience more peaks and valleys and get hungry faster.

Source: Halberg, et al., Effect of intermittent fasting and refeeding on insulin action in healthy men, Journal of Applied Physiology, 2005

How to try fasting: A step-by-step guide

If you decide to go on an occasional fast, make sure you eat healthy first and do it in steps:

Start with just 3 meals a day and no snacks

First, start with just three meals a day, but with no more snacking in between meals.

Choose meals with no carbs or very complex carbs, with a low glycemic load, high in fiber, without added sugars, rich in healthy fats, and lots of vegetables.

Vegetables are high in fiber which is filling and suppresses your hunger pangs.

Then, experiment with skipping a meal

If this works and you want more, experiment with skipping a meal or eating your meals in a limited window. Usually, it fits your biological clock better to skip the evening meal first.

But this can vary from person to person. For example, some people hate breakfast and may be able to start by extending the normal overnight fast by eating breakfast later.

It’s a matter of figuring out what suits you personally.

Finally, go without food for 18 to 24 hours

The final step is to start fasting with 18 to 24 hours of no food.

Make sure to drink plenty of water during your fast.

You can only do this after you have correctly completed the previous steps.

Suppose you still eat too many sugary foods and fast carbohydrates. In that case, you will get hungry quickly, the fasting will not succeed, and you will eat many unhealthy things to compensate, negating the effect of the fasting.

Careful with longer fasts

Be careful with fasting for 48 hours. You don’t want to end up in some sort of disciplinary regime.

If it all hinges on willpower, you might last a week or a month before throwing in the towel. Then you are often back to square one.

Choose something that suits you. And if it doesn’t work for you, just don’t do it.

What does intermittent fasting do to your body? Conclusion

You do not have to fast to live healthily, but it can have advantages.

Although the scientific research on fasting is still ongoing, trying this is much less risky than trying a new drug with unforeseen side effects.

In particular, fasting seems to have great potential to break the deadlock in people with diabetes or severe obesity.

About Heather Campbell

As a nutritionist, my field of specialization is science-based nutritional advice but more importantly, it is my goal to share capturing and inspiring stories, examples and solutions which can help plus-size individuals overcome their specific difficulties. Read More