I’ve always been a firm believer in acquiring knowledge.
But today’s society, most people seem more concerned with getting quick answers than actual knowledge. Think about it – how many times a day are you told on social media, email newsletters, advertisements…etc., that you should be doing [blank] because it’s the best/quickest/most effective solution for [blank].
This is because as marketers, they know that people are mostly concerned with results – the finish line. Not necessarily understanding the journey or the process.
And sometimes that’s okay – a lot of us don’t necessarily want to know every single detail as to how the body burns fat, digests food, or how the gut microbiome works.
They’re just tired of looking and feeling subpar and they want that to change. I get that.
However, when it comes to something like intermittent fasting, understanding the process of how it works, (ex: the effects of intermittent fasting on the body) is incredibly important for a couple of reasons:
One – while it’s perfectly safe for the majority of the population, intermittent fasting is a form of stress on the body. You’re intentionally restricting calories to facilitate physical & mental benefits.
Any IG influencer can throw around terms like ketosis, autophagy, & insulin sensitivity. But the truth is if you have no idea what those processes are, why they are beneficial, and how they are achieved within the body…then you’re doing yourself a massive disservice when it comes to learning about how to improve your health versus just blindly following instructions.
Two – To the average person, intermittent fasting is very strange, even “crazy” concept. Because of this, a popular piece of advice for people who fast is to avoid bringing it up in public situations, as most people will end up trying to talk you out of it. Whether that be from concern over your safety or their insecurities, it can be an exhausting conversation regardless.
A simple “I’m just not hungry” is always the best option in these type of situations, but for the times in which you feel like you want to explain why you’re fasting and why you believe in it so strongly, having the knowledge as to how it actually works within the body will shut down any doubter in their tracks.
Now if you’re worried it’s a little too complicated to explain and/or learn – never-fear. Because I have created this helpful “cheat-sheet” to show you exactly what goes on in the body during a fast – from your last bite of food to 5 days!
Not only will this be vital to your understanding of how fasting works, but I will also provide a fasting schedule example for those looking to maximize benefits, without totally disrupting their daily schedule or lifestyle.
Let’s dive in!
We’ll start with Your Fed-State
Before we get to fasting, we need to begin with what most people around the country are perpetually in every hour of every single day: Your fed-state.
When you consume food, your body is in growth mode. Insulin signaling & mTOR pathways tell your cells to grow, divide, & synthesize proteins.
For those that don’t know, insulin is a hormone made by the pancreas that helps glucose in your blood enter cells in your muscle, fat, and liver, where it’s used for energy.
When your cells have their necessary energy requirements, that’s when the insulin starts to promote fat storage within the body, especially when you lead an inactive lifestyle and are constantly over-consuming your caloric needs.
The “mammalian target of rapamycin” or mTOR is a protein, originally discovered in yeast, that controls cell growth and metabolism in response to nutrients, growth factors, cellular energy, and stress
When mTOR is activated (by consumption of protein or carbs) it’s telling your cells to shut down autophagy. Autophagy is a recycling and cleanup process that rids your body of damaged and misfolded proteins (we’ll talk about this in more detail later).
Neither insulin nor mTOR is inherently bad and both are a necessary part of human life. However, when activated too much or too frequently – both can lead to diseases such as diabetes and cancer respectively.
Therefore, if you’re trying to burn body fat & improve your long-term health, integrating some type of fasting routine is imperative because this will finally allow your body to stop producing insulin and triggering mTOR.
But to do this, you need to make it past the 12-hour mark without food. This is the amount of time required for insulin levels to go completely down and for the body to leave its fed state and finally reach its fasted state.
At this time, your body starts to flip the “metabolic switch” in which glucose levels are now down and it begins using your stored glycogen (in the liver) and starts producing (limited) ketones.
Aka – the cool stuff starts to happen.
Your Fasted State
To keep things organized, I’m going to break your fasted state into five different sections based on how long you’ve been fasting. In each section, I’ll list:
• What happens during this time
• The benefits you’ll receive
• And best practices for implementation into your lifestyle
What happens during this time?
As I mentioned previously, once you’re past 12 hours, the body begins to flip the switch from using primarily glucose from your diet to converting stored glycogen into glucose as an energy source.
Depending on your diet and activity level, you’ll also begin to start producing ketones as your body starts to break down stored body fat as an alternative fuel source.
You can gather that the main benefit during this stage is fat loss. This is a big reason as to why some studies have shown that when you compare groups of people with similar calorie consumption and activity, that group that practiced some form of intermittent fasting had a greater reduction in body fat mass.
However, what is often overlooked is that when you start to experience this blend of glucose and ketones, your body is becoming much more metabolically flexible, allowing you to be less reliant on food for energy.
Whether you’re a fan of fasting or not, I recommend that EVERYONE have a minimum of 12 hours between his or her first and last meal on semi-daily (if not daily) basis. There is absolutely no reason to be in a fed-state 24-hours day.
My recommendation would be to implement at least one fast of 16-18 hours per week (there’s a great book about this called the 17-hour fast), but feel free to do this daily if it supports your goals and lifestyle as it has for me.
Remember, fasting isn’t always about restricting calories; it’s about restricting the window in which you’re consuming your calories.
What happens during this time?
Once you reach the 18-hour mark, a couple of really cool things within the body start to occur.
Firstly, you begin to enter a deeper state of ketosis. What this means is that your body is now running very low on glucose/glycogen, and almost having to rely entirely on body fat for fuel. This creates a feeling of mental clarity that I’ll explain in the benefits section below.
Secondly – remember when I mentioned autophagy? This the time that begins to occur as well.
As I mentioned previously, autophagy is a recycling and cleanup process that rids your body of damaged and misfolded proteins and is the opposite effect of mTOR. This creates a balance of processes within the body for optimal human health.
By stimulating autophagy, you’re essential allowing your body to clean and heal itself naturally, therefore preventing disease and the need for expensive medication in the future. Not only that, but it has an incredible anti-aging effect, both for your skin and the health of your mitochondria – which are essential for you longevity and vitality as we age (I’ll dive deep into mitochondrial health in a later post).
Additionally, because of the increase in ketones in the bloodstream, you begin to receive a feeling of focus and mental clarity as well. This is why you see many busy professionals and CEOs practice an OMAD (one meal a day) style of fasting, so they can take advantage of this feeling while saving time and improving their overall health simultaneously.
Depending on your caloric needs, lifestyle, and schedule – you can perform a fast of this length (or max 23-hours) daily if you want to. However, I feel as though it’s much more sustainable to do this 1-2 times per week, especially on off-days when you’re taking a break from the gym or resistance training.
What happens during this time?
Okay, now is where things start to get interesting…if you can work your way up to a fast of this length. During the 24 to 48-hour mark, your human growth hormone (HGH) increases by 5 times its regular levels. This is why you can fast for this length and still preserve your lean muscle mass.
Additionally, you receive the biggest surge for autophagy (330%) and begin to enter a very deep state of ketosis.
With this large of a boost in HGH, you’re likely to see significant strength gains in a week or two after you complete a fast of this length. Also, this is the period where you’ll see the biggest increase percentage-wise when it comes to autophagy. While it takes up to 5-7 days to fully maximize the benefits from autophagy, by fasting for around 36-48 hours, you’re getting about 90% of the benefits with a much more reasonable fasting period.
It’s also important to note that hunger usually peaks around the 48-hour mark, so if your goal is to go longer, getting by this marker will most likely be the toughest physical challenge you’ll have to overcome.
Again, as I’ll say repeatedly, frequency comes down to goals and lifestyle. Having said that, my recommendation is for a fast of this length 1-2 times per month, which will provide the benefits mentioned without impeding too much on your day-to-day schedule & routine.
Each month take a look at your calendar and plan a day or two that you think it would be easy to implement so that you don’t end up constantly putting it off.
What happens during this time?
As someone who coaches people and frequently gives out fasting advice, this is usually the maximum amount of time I recommend that someone fast, especially if you’ve only been doing it for a year or so.
By 72 hours, your body is breaking down old immune cells and generating new ones and insulin is at its lowest level. As mentioned, autophagy continues to grow (albeit very slowly), you continue to burn body fat for energy, and this is usually the longest amount of time you can fast before possibly starting to lose some of your lean muscle mass.
During this time, your body is beginning to completely reset and re-vitalize.
Because you’ve been in ketosis for so long (and hopefully been active in the form of walking), you’ve most likely been able to burn quite a bit of stubborn body fat as well. This is the big difference between being in ketosis while fasted (burning stored body fat) versus being in ketosis while on the ketogenic diet (burning fat calories from food).
And because insulin levels are so low, your insulin sensitivity gets a nice reboot once you do break your fast. As I mentioned, this is the maximum length of time I’d fast if preserving muscle is important to you (which it should be). This can be mitigated by doing some light resistance training during your fast, but you need to be very experienced to accomplish this.
If you’re really into fasting, you can potentially do this one time per month. My recommendation is to do it 1-2 times per year, or maybe quarterly if you can make it work.
What happens during this time?
This is for experienced fasters only. I have done a 5-day fast, and while it wasn’t quite as difficult as you may expect, it most certainly wasn’t easy.
During this period, autophagy will eventually peak and your entire immune system will get a massive “reset” as well. Additionally, your gut begins to produce different beneficial enzymes and your body goes through complete detoxification.
Without going too much into the weeds, as this is still a subject that needs more research, fasting for this length of time can do wonders for your overall health and longevity. While you may lose a bit of muscle mass and the mental grind of 5-days without food can be tough, it will pay massive dividends for you down the line.
On another note, fasting for length creates an incredible amount of discipline & reliance within you that can only really be explained if you experience it yourself.
One time per year max. Can you do more? Sure, but honestly from someone who’s done this, one time is more than enough in my opinion.
Putting it all together
So I know this may seem like A LOT. But if you’re someone like me, who’s both active, busy, loves to eat, has a social life, and wants to prioritize your health & longevity – there’s an incredibly easy system to follow in which you can receive ALL of these fasting benefits of the course of a year.
Here’s a sample of my breakdown, but feel free to adjust based your lifestyle & goals:
Daily: Fast for 12-16 hours at a minimum. This is because it works for my lifestyle and I’m rarely hungry in the morning when I wake up.
2 days per week, usually on off-days from the gym or when I’m really busy, I’ll extend my fast to 17-20 hours.
One time per week or every other week, I’ll try to do a 24-hour fast.
At the end of each month, (if it works for my schedule) I will do a 36-48 hour fast.
At the beginning of the year and 6-months in, I will do a 3-5 day fast.
This schedule allows me to receive all the benefits from fasting for different lengths of time, supports my goals, but doesn’t cause major inconvenience with my routine or social life.
To me, that’s the golden trio when it comes to intermittent fasting as a lifestyle.
If you enjoyed the article, please leave a comment below and let me know!
Thank you for reading.