Intermittent fasting makes you tired – but isn’t it supposed to increase your energy?
You’ve heard so many benefits of about IF, but you find it just leaves you with fatigue.
Fasting, as I’m sure you know, involves voluntarily withholding food for a long time, usually a number of days. Intermittent fasting does a similar thing, but for hours instead of days.
Most intermittent fasts last 12-18 hours. Let’s say you ate dinner yesterday at 18:00. On an intermittent fast day, you would skip breakfast and not eat again until lunch (12:00). This would result in an eighteen-hour fast. That’s why intermittent fasting is more comfortable, resulting in minimal hunger pangs.
But is intermittent fasting healthy for everyone?
Intermittent fasting 101
For millions of years, humans have fasted. Think of your paleolithic ancestors – do you think they had access to breakfast, lunch, and dinner every day? Three square meals a day is a modern convenience. Your ancestors fasted out of necessity – there were times of the year when there wasn’t enough food.
Fortunately, you don’t have to worry about food shortages in the modern world. But eating like your ancestors is one of the healthiest practices you can undertake. And restricting your food intake may be a great way to make your cells healthier – something you need to do if you’re dealing with fatigue.
How do your cells cause fatigue?!?
When you eat, more calories (energy) are taken in than are immediately needed. The leftover calories are stored for later. These calories are often stored in your liver as glycogen – but only up to a certain point. If your glycogen stores are full, your body is forced to store this excess energy as fat.
When you fast, the opposite of fat storage occurs. Your blood sugar falls, signaling the need to mobilize sugar for energy. Your body will first use its glycogen stores. But these only last for hours (depending on how much food you’ve consumed). After that, your body begins using fat for fuel. When you consciously restrict food through fasting, you force your body to burn its fat stores for energy.
These are the two states your body can exist in:
- A fed/energy storage state.
- A fasted/energy mobilization state.
Either you’re storing energy or you’re using it. If you’re overweight, you’ve spent more time storing energy. If you’re experiencing a famine, you’re in the mobilization state. For many in the first world, your default state is energy storage.
Intermittent fasting helps to move your body from energy storage towards energy mobilization. Doing so can be a great way to increase your energy levels. But it’s not for everyone.
Who is intermittent fasting for?
The easier question to answer is who intermittent fasting not for. There are people that should definitely not intermittent fast. And there are others, like those with chronic fatigue syndrome, where the answer is not so clear.
Who should NOT intermittent fast?
- Those pregnant or breastfeeding
- During these times your body needs the excess calories to create nutrients. Consciously restricting calories is not recommended.
- Much like pregnant or breastfeeding women, children need nutrients to develop. Intermittent fasting can restrict nutrients vital for growth.
- Underweight individuals
- If your BMI is less than 18.5, intermittent fasting is not recommended. You do not have the necessary fat reserves to ensure healthy energy mobilization.
These are the people who should not practice intermittent fasting.
But there are others that also may not react well to intermittent fasting.
Should women fast intermittently?
Your brain signals to your ovaries to release female sex hormones like estrogen and progesterone.
If your brain thinks there is stress in your environment, it will alter your hormone cycles. This ensures that during periods of intense stress (say, mass starvation) your body would struggle to get pregnant. Getting pregnant during a famine is dangerous for both mom and baby.
When it comes to intermittent fasting, women need to deal with more hormonal fluctuations than men. Fasting signals to the brain that there is stress – a decreased availability of calories. If done for too long or too intensely, intermittent fasting can negatively affect your hormone cycles.
In general, I recommend women stick to the following guidelines when intermittent fasting:
- Avoid fasting or calorie restriction on exercise days.
- Do not practice intermittent fasting every day.
- Instead, space the days out through the week. Try for three days a week. Put a day without fasting in between each of your fasting days.
- Do not fast for longer than 12-16 hours.
By following these recommendations, you’ll place only moderate stress on your body. This stress should be small enough that it does not affect your hormonal cycles.
Should you practice intermittent fasting if you have adrenal fatigue?
Your brain releases cortisol when you are under stress. People with adrenal fatigue have low levels of cortisol. When you intermittent fast, you place a (mild) stress on your body.
Did you know there are different types of adrenal fatigue?
If you have severe adrenal fatigue, you may find that intermittent fasting leaves you feeling weak. That’s because intermittent fasting could lead to low blood sugar (hypoglycemia) as your body does not have enough cortisol to balance your blood sugar. If this is the case, you will find intermittent fasting can also cause:
- Extreme hunger
- Feeling dizzy
But if your adrenal fatigue is caused by blood sugar imbalances, intermittent fasting may be the perfect solution.
If you have adrenal fatigue, experiment with intermittent fasting for a couple of weeks. If you do not feel well when fasting, do not continue. The key to intermittent fasting with adrenal fatigue is moderation. Do not fast for too long or too often. Much like exercise, the stress needs to be within your body’s tolerance zone.
If you want the blood sugar-stabilizing effects of intermittent fasting without fasting, check out my digital course. In this course, I show you how to identify which foods cause give you energy and which foods make you sleepy. By the end, you’ll have perfect blood sugar balance and no more fatigue – all without having to fast!
Should you intermittent fast if you have chronic fatigue syndrome?
This is a very challenging question to answer. Chronic fatigue syndrome has a variety of different causes, and if it’s caused by a cortisol deficiency, intermittent fasting might make it worse. If you want to see how IF affects CFS I highly recommend working with a qualified Functional Medicine professional.
The true driver of CFS is decreased mitochondrial function. Mitochondria are the parts of the cell that create energy.
For now, I will focus how intermittent fasting affects the mitochondria.
I break down how your mitochondria cause fatigue in this post
It seems like a contradiction, but your mitochondria are more efficient when they are put under calorie restriction. (1)
Basically, that’s because restricting calories – like intermittent fasting – decreases cellular aging and promotes much healthier and vital cells.
If you have CFS, your mitochondria are not functioning well. Intermittent fasting could be the perfect way to improve your mitochondrial function!
Intermittent fasting and the keto diet
My general recommendation for people with chronic fatigue syndrome is to follow a ketogenic diet. Intermittent fasting pairs very well with this. You should try to eat all of your daily calories within a ten-hour window. This allows the glycogen stores in your liver to run out, forcing your body into using fat for fuel.
If you don’t have the energy for radical dietary changes – like those found in a keto diet – worry not! I have the perfect solution for you. My digital course, Stop Feeding Fatigue, guides you through nutrition change. This nutrition change:
- Is easy,
- Requires little energy output,
- Will increase your energy!
When your mitochondria use glucose for energy, they produce 38 molecules of ATP for each molecule of glucose. But when your mitochondria use fat for energy, they’re able to produce 128 molecules of ATP for each molecule of fatty acid. This is a far more efficient system.
Restricting your food consumption to a ten-hour window encourages your body to burn fat for energy instead of sugar. As a result your mitochondria are happier and produce more energy.
If you have CFS you need to start intermittent fasting slowly. Try not to restrict your total daily calories by more than 500/day when starting. As your body becomes keto-adapted (fat-adapted) you can start lengthening your fast.
Again, I highly recommend this be done under the supervision of a qualified Functional Medicine practitioner.
How to intermittent fast like a pro
Think of fasting like a muscle. You’re not going to go to the gym for the first time and put 500lbs on the bar and successfully do multiple reps of back squats. Instead, you might start with bodyweight squats. Or, maybe by just squatting the weight of the bar.
A similar rule applies to fasting. Don’t start your fasting journey by going right into a 18:6 fast. It’s uncomfortable and highly stressful for your body. Instead, start with a small, 10-12 hour intermittent fast. Do this one day a week.
Once that’s comfortable, add in another day. Slowly. Then, try increasing your fast. An eighteen-hour fast is a good next step. When you’re at the point where doing an eighteen-hour fast is easy (and you’re not feeling hunger pangs), you’re ready to move to a twenty-four hour fast.
Remember, take it slow. Build your fasting muscles up over time. This is a marathon, not a sprint.
Please do not attempt a fast longer than three days without being under the care of a qualified medical practitioner. Long fasts present health risks that are beyond the scope of this post.
Want to learn more about chronic fatigue syndrome and energy production?
Ok, there you have it, you know who intermittent fasting is best suited for and how to combat intermittent fasting fatigue!
Now, I want to hear from you!
What effect did intermittent fasting have on your energy levels?
Leave your answers in the comments section below!
Hello, I am concerned for a human being that has declined in health in the last year, from Lyme. He insists on fasting long period, shorter period than when he was healthy, like a few days, but mostly fasts because hes not hungry. He s a vegan. Energy level low, doesnt exercise, claims he was a marathon runner once. His body is underweight. Only 33 yrs old.
Hes had his blood filtered, and magnetic therapyy two months ago, which seemed to improve his vitality, but this last month he has been in bed. Can you suggest anything, and is fasting a productive long term solution? I think hes too weak and underweight to fast. also, his intake of rice was pretty high few months ago , all i know is he has studied what foods are better for him.
Mark Volmer says
This sounds quite serious. I recommend your friend find a Lyme-literate physician ASAP.
Here’s a list of some stellar practitioners – https://www.survivingmold.com/shoemaker-protocol/Certified-Physicians-Shoemaker-Protocol
Intermittent Fasting is a fad eating lifestyle. It’s not sustainable. I’ve tried it on several occasions for long periods and it doesn’t work as advertised. People said I looked sick. I always went back to 3 small meals a day for a better body and more focused mind. Our brains use the most calories, so not eating breakfast will reduce quality of work, and cause tiredness and may lead to depression.
Avoid intermittent fasting!!! Eat 3 small meals a day. No snacking in between! It’s okay to have hunger pains between meals. Hunger pains between 3 meals (breakfast, lunch, dinner) is the only “fast” you need.
Mark Volmer says
If you think back to our hunter-gatherer ancestors – which makes up 99% of the time humans have been on this planet – it’s highly unlikely they had access to three square meals per day. Three meals a day is a modern construct. In all likelihood, our ancestors would have been fasting on a regular basis.
But I completely understand why you don’t feel good doing it. Try lowering your daily total carbohydrate intake. This should help push your body into ketosis. And once you’re burning fat for fuel, fasting will feel easy, your mind will be sharp, and you should feel energized. More info on lowering your carbs here, here, and here.
Thanks so much for the comment!
I e been fasting since June, I think I’m finally at my last glycogen stores, I feel week and tired, what do i need to do my muscles hurt walking up the stairs everything an effort how long before i go into fat burning mode, i craved sugar i gave back in I’m back being strict to push myself through how much longer will it be please,?
Mark Volmer says
It sounds like you’re dealing with a low-carb but not quite ketogenic diet. It’s not a fun place to be. More info on how to fix that here 🙂
My husband and I started intermittent fasting a few months ago after learning the health benefits from our son. We have also started occassionally fasting for an entire day. While my husband and son both feel more energized when doing a full fast, I do not. I also found out last week that I have Adrenal Fatigue ( low coritisol levels) After reading your post I realize that may be the reason a full fast is making me tired, as opposed to energized. Thank you for this information.
Mark Volmer says
Good call on scaling back those fasts of yours. Let your energy be your guide – if you’re feeling tired, it’s time to eat. If your energy feels good, keep on fasting!
Keep up the great work!
Hi, I started intermittent fasting. I take breakfast at 10am and then Have fruits or veggies at 2 or 3pm and evening 5:30 one coffee and 7:30pm finish my dinner.
I am doing this from past 3 days and I have observed I am feeling to take a nap at 12pm.
Sometimes I feel the need more and take a 30 minute nap.
Is this something I should be concerned about ?
Mark Volmer says
3 days is too soon to make a decision. Try it for ~2 weeks. If your fatigue hasn’t improved, then it’s time to alter your eating schedule!
HI there, I realize this post is a year old but I’m just finding it now. I’m a woman who has started IF 6 days ago. Up until then, I wouldn’t eat until noon most days, but my eating window would go pretty late at night 9 or 10. Since starting IF I have been going for 18:6 and mostly have ended up 19:15. For days I felt amazing, had good energy, and really I don’t feel hungry, even when my window opens. But on the 4th day I got pretty weak feeling, and it happened again today on day 7. I can’t tell if my electrolytes are low, or if my blood sugars are low. I read you don’t advise doing it everyday, but I am trying to lose 25 pounds I have put on over the years, and have lost 5 this week, probably mostly water. My question is – why would I feel just great some days and so bad on others? How can I tell if it’s an electrolyte imbalance or low blood sugar? I am 52 and otherwise healthy.
Mark Volmer says
I say start with adding electrolytes. See if that helps improve your frequency of fasting.
Fasting is a stress – albeit a small (hermetic) stress. But if done too frequently – and what is too frequent is unique to the individual – you’ll definitely notice adverse reactions. Listen to your body. Go slow. Think of this as a marathon 🙂