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Fasting For Weight Loss

This blog post was created to explain the how fasting works and how it affects weight loss and health long term.


Before we get into the benefits, there are many different ways you can fast. Basically, fasting means going a certain period of time without eating or drinking anything that has caloric value. Basically all foods are to be avoided, only drink water or tea throughout the fast in order for the fast to be as effective as possible. Do not add sugar or milk to the tea, just plain tea is allowed during a fast.

Some of the main ways to add fasting to your lifestyle are:

Short fasts - 12:12 fasts, 14:10, 16:8 and 20:4 daily fasting (the first number represents the hours fasting and the second number represents hours that eating is allowed. For example - the 16:8 means that 16 hours of the day is fasting and 8 hours are eating, meaning that you could eat from 11am to 7pm everyday, anything outside of that is fasting, as an example.)

Long fasts - 24 hour, 36 hour and 48 hour fasting once a week. Most common would be a 24 hour fast meaning that you eat breakfast on a monday at 7am and your next meal would be breakfast on the tuesday at 7am.

All these fasting times are all valuable when it comes to health and weight loss, one is not superior to another and each fasting period will affect everyone differently. This could be due to many reasons that are out of our control such as genetics and gender. Choose one that best suits your lifestyle. You could always change your fasting times to try out different times and how they affect your body. Trial and error until you find one that works the best for you.


Now we know what fasting is and how long we can choose to fast for, let us go through what the benefits of fasting is and how it improves health and weight loss.


Firstly, let's see how our bodies respond to fasting. Glucose (carbs) are our bodies main source of energy followed by fat, so if glucose is unavailable for our bodies to use, we will start to turn to fat with no real health detriments. This is a natural part of our lives, during paleolithic times, periodic food scarcity was common between hunts and we have evolved to deal with this food scarcity. What we are talking about here is that humans are good at dealing with no food for extended periods of time, our bodies transition from glucose (short term energy) to fat (long term energy). Among other functions, fat is really just our stored food energy that we use when it is needed.

The transition from fed to fasted goes like this:

  • After we eat, we digest food, insulin rises and we use the glucose as energy.

  • After we don't eat for a few hours, insulin begins to drop.

  • When we fast for longer periods, ketosis begins to happen which is where our bodies break down fat and use it as energy.

  • Protein conservation occurs after long period of fasting meaning that our Human Growth Hormone (HGH) maintain muscle mass and lean tissue. The energy needed for our basic metabolic needs are met by our fatty acids. This means that the myth of 'fasting burns muscle mass' is false.

Now we know how our bodies respond to fasting, we will now go and have a look at how this improves weight loss. The key here is the hormone insulin, the hormone that holds the biggest responsibility when we talk about weight gain. Weight loss or weight gain is mainly a hormonal function, so we need to look at how we can control these hormones in order to lose weight (read Understand How Weight Loss Works blog for further understanding). So if insulin is mostly responsible for weight gain, common sense would tell us that reducing our production of insulin would be a good idea. So let's talk about how fasting controls insulin production.


When we eat foods that are high in carbohydrates, our bodies need to produce insulin to move the glucose out of our blood and into our muscles or liver for quick energy use. Proteins also affect insulin production, but not as much as carbs. Fats have limited effect on insulin production. So when we talk about fasting, it is a time where we do not consume anything that has caloric value. Put very simply, when we don't eat anything, we give our bodies a chance to stop constantly producing insulin. Fasting is one of the most efficient and effective ways for us to lose weight as it is very effective at reducing insulin production. All foods raise insulin, even if it is very limited, so the best option to not raise insulin at all is to not eat at all.


When we fast, it gives our bodies a chance to reset itself hormonal wise. We live in a society that is all about convenience, whenever we want food, we can get it straight away delivered to our doors. This means that we are constantly eating and snacking most times of the day. The only time we don't eat for a decent amount of time is when we are sleeping. And even our sleep is shown to be getting shorter and shorter due to the fast paced society we live in. So if we are always eating, that means that our insulin levels are always high due to the need for our bodies to control blood glucose levels. It never has a chance to reset and lower itself. If insulin is one of the main causes of weight gain, having it being produced 24/7 is obviously not a good thing.


Regular fasting has also been shown to lower the risk of insulin resistance. This is because the more we are constantly exposed to insulin, the more our cells will adapt to its effects and the higher chance our cells will become resistant to it. However, when we fast, our bodies insulin levels drop as we stop producing it rapidly. This also gives our cells a chance to reset and cleanse itself before having to absorb glucose again. This process of cleansing is called autophagy. If we imagine that we never cleaned our house, we have things everywhere and everything is dirty. This is basically our bodies everyday from going through daily processes such as digestion, this is called oxidative damage. When we fast we allow our bodies to clean itself up (to put it simply) which is the process of autophagy. This will significantly reduce the chance of insulin resistance and therefore reduce the chance of diabetes.


I also wanted to address two myths about fasting:

  1. Fasting will make us lose muscle mass - as stated above, our bodies Human Growth Hormone will maintain our leans tissue and muscle mass and we will use fatty acids as energy instead. Our bodies will always lean on fats as energy before it thinks about going to protein. The only time we use proteins and lean mass as energy is in cases of extreme starvation where our body fat level is below 4%. So this is highly unlikely meaning that it is not a concern.

  2. Fasting will reduce my metabolic rate - this is simply not true. Reduction of metabolic rate only comes when we reduce our caloric intake. Our bodies only use what it is given, so if we reduce our caloric intake under our daily caloric needs, our bodies will adapt by slowing down our metabolism. If we are constantly exposed to low calorie intake, we will adapt by lowering our energy expenditure, it is that simple. What we must remember is that fasting is not reducing calories, fasting is reducing our eating time frame. We should still eat our daily required food, we just eat it inside the hours that we are not fasting. If we ate 2000 calories a day before we fast, we should still aim to eat those calories, however, just within the time frame when we are not fasting. If we don't want to stuff ourselves with food in the short amount of time, we can easily add more calorie dense foods to our meals such as adding olive oil as a dressing. Adding olive oil won't make our meal much more filling, but it gives a lot of good calories. The main point it, fasting is not calorie reduction, it is insulin reduction.

When we are outside of our fasting period, we also need to make sure we eat the right foods. Fasting won't help if we eat processed foods everyday when we aren't fasting. As stated above, read the Understand How Weight Loss Works blog to understand what foods we should stick with and what foods causes weight gain.

I hope that this blog has helped your understanding on fasting and how it is beneficial for health and weight loss. I hope we can all start to implement some type of fasting in our lifestyles!


*If you have any conditions that affect blood sugar such as diabetes, please consult your doctor before you start any sort of fast.

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