Understanding The Negative Effects Of Fasting – The Lowdown

Understanding the negative effects that occur whilst fasting is an important step to take before beginning a fast as you need to have an idea of what symptoms you may feel in what is a normal transition into ketosis.

Recognizing these side effects can help to determine whether what you are feeling is an effect of the fast or another underlying medical condition.

Please view my medical disclaimer before reading on.

What Happens When You Begin To Fast

When you stop eating for a certain period, your body will enter into a state of ketosis, which is where your body will begin to use ketones from fat as its primary energy source, rather than the glucose that is produced from carbohydrates.

A person can survive quite some time during ketosis, as long as there is adequate hydration and fat reserves. It is not recommended that people underweight should fast for prolonged periods.

Your body is trying to adjust to different energy source, the ketones, and you’re not relying on blood sugar for energy. You are burning fat for energy which ensures that your blood sugar does not rise or fall sharply. You will usually have more energy and better mood and brain function.


Give Your System A Good Flush Out

Your body also begins a process called autophagy, where old cells are broken down, cleaned out and regenerated to form newer healthier cells.

You may encounter headaches, fatigue, constipation, bad breath, nausea and muscle cramps during a fasting period. Awesome!

Headaches from fasting are very common and are generally caused by low blood sugar and/or lower sodium levels and are very normal, particularly in the first couple of days of fasting, but are not usually debilitating and should pass.

Brain Fog!!

You may notice too that in these first few days you will feel a bit foggier in the head than you usually would be when you wake up. This is very common and will sometimes hit you at various parts of the day, not just the morning.

You may also feel drowsy or lethargic during this period as well. This is also normal and should pass around day 3 or 4 of your fast, but can vary based on the type of fast you are undertaking.


Many of the effects mentioned above happen because your body is breaking down fat, old dead cells and other toxins in your body. Toxins that have accumulated over years. This all has to come through your blood stream and this can make things uncomfortable for you and is all part and parcel of the detoxing process.

The best thing to do for this, is just make sure you are keeping your fluid levels up and sometimes drinking some homemade juice can help give you that sugar boost you need to get you back on your game.

Try to ride it out as best you can, it will pass and if you can find somewhere to rest for a bit until it passes, then this is the best option. Don’t push yourself if not feeling so great, it won’t help in this situation.

How About… Umm… Pooing??.. Sorry… It Needs To Be Said…

Constipation is common during fasting due to lack of fiber and lack of food in general. Personally, I have not taken any fiber supplements during a fasting period and have just let things run as they please (Pardon the pun). I have not felt any real discomfort in this area.

I have found that after 3-4 days, I will pass the occasional little poo, but that’s about it. Mind you, it’s real stinky bugger. One that seems like it’s been there for months or years. Probably because it has…

Your body really has a good clean out of its system when food is not being processed and your body can get rid of old waste that’s been sitting in your system for a while.


Please, Don’t Breath On Me…

One of the other nice side effects of fasting and ketosis is bad breath. This is caused by an elevated ketone level, and acetone, which is a ketone body and the main source of the smell, will exit through your urine and breath. Whilst it might be great for your diet, it might not be great for your social life! Just be aware of it and brush your teeth and chew sugar-free gum if it becomes a problem.

If you suffer from gout, sometimes the rapid weight loss from fasting can cause your uric acid levels to rise and cause a gout attack. I have only experienced a gout attack once out of the many times that I have fasted, but it is something to be aware of.

As a general rule, I will avoid taking any pills during a fast, so when encountered the gout attack, I discontinued the fast in order to address the issue, as the pain was fairly bad and was not going away in a hurry.


Sounds Like A Ton Of Fun….Not!!

The above effects are some of the most common associated with fasting and ketosis but should not be feared. Just understand that what you are feeling is normal and is part of what is known as the “Keto Flu.”

Allow your body to heal, rejuvenate and cleanse itself in the fasting process and know that you are doing a great thing for your body in the long run.

Knowing about the negative effects of fasting should help you prepare mentally for what’s install for you during this period. These feelings are usually felt the worst during the first few days when your body is adjusting to the change. Just try to roll with it, stay hydrated and rest when you can.

Please feel free to leave your thoughts in the comments below or contact me here.

The Red Door

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