Does Intermittent Fasting Cause Fatigue?

The health world is abuzz with the benefits of intermittent fasting. But will those with chronic fatigue syndrome get the same benefits? Or, could intermittent fasting actually make you more tired?

For the uninitiated, intermittent fasting is a voluntary withholding food intake for a short period of time. Fasting, as I’m sure you’re already familiar with, involves voluntary 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. Intermittent fasting in this fashion is the most 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 improve your mitochondrial function — something you need to do if you’re dealing with fatigue.

When you consciously restrict food through fasting, you force your body to burn its fat stores for energy. 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.

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 in the energy storage state. 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 is not for. There are generally agreed upon populations that should not intermittent fast. And there are other populations, like those with chronic fatigue syndrome, where the answer is not so clear.

Who should avoid intermittent fasting?

  • Those pregnant or breastfeeding
  • During these times your body needs the excess calories to create nutrients. Consciously restricting calories is not recommended during these times.
  • Children
  • 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 clear-cut populations that should not do intermittent fasting. But there are other populations that may not react well to intermittent fasting.

Should women utilize intermittent fasting?

The HPA (hypothalamic-pituitary-adrenal) axis combined with your gonads is the master control center for female hormones. It’s your brain that signals to your ovaries to release female sex hormones like estrogen and progesterone.

Should your brain perceive there to be stress in your environment, it will alter your hormone cycles. This ensured that during periods of intense stress (say, mass starvation) that your body would struggle to get pregnant. Getting pregnant during a famine results in a lowered survival risk for both mom and baby.

When it comes to intermittent fasting, women need to contend 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 adhere to the following guidelines when intermittent fasting:

  • Avoid fasting or calorie restriction on exercise days.
  • Do not perform 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.
  • Fast for 12–16 hours. Not longer.

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 those with adrenal fatigue utilize intermittent fasting?

Cortisol is the hormone your brain releases in times of stress. Those with adrenal fatigue have low levels of cortisol. When you intermittent fast, you place a (mild) stress on your body.

If your adrenal fatigue is severe, you may find that you do not tolerate intermittent fasting at all. Intermittent fasting could lead to low blood sugar (hypoglycemia) symptoms as your body does not have enough cortisol to balance your blood sugar.

But if your adrenal fatigue is caused by blood sugar imbalances, intermittent fasting may be the perfect solution.

For those with adrenal fatigue, I recommend intermittent fasting be experimented with for a couple weeks. If you do not feel well when fasting, it is not recommended you 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.

Should you intermittent fast if you have chronic fatigue syndrome?

This is a very challenging question to answer. Chronic fatigue syndrome comes about from a variety of different causes. The generally agreed upon presentation of CFS is decreased mitochondrial function. For this blog, I will focus on intermittent fasting through the lens of mitochondrial function.

Please note that for those with chronic fatigue syndrome, working with a qualified functional medicine professional is essential. There are many moving parts to this illness. Should your fatigue be caused by cortisol deficiency, intermittent fasting may make your fatigue worse.

It seems paradoxical, but your mitochondria function better when they are put under calorie restriction. They become more efficient when this occurs. Inside your cells, mitochondrial networks generally alternate between two states: fused and fragmented. One study found that calorie-restricted diets promote homeostasis in mitochondrial networks allowing for healthy plasticity between these fused and fragmented states. (1)

Said another way, restricting calories — like intermittent fasting — decreases cellular aging and promotes much healthier and vital cells.

If you have chronic fatigue syndrome, your mitochondria are not functioning at optimal levels. Performing intermittent fasting could be the perfect activity for you to improve your mitochondrial function!

My general recommendations for those 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 utilizing fat for fuel.

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 into a ketogenic state — burning fat for energy instead of sugar. The resulting effect is happier mitochondria and more energy.

Those with chronic fatigue syndrome should 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 duration. Though I 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 attempting a multiple day 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 the duration of 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.

Ok, there you have it, you know who intermittent fasting is best suited for!

Now, I want to hear from you!

What effect did intermittent fasting have on your energy levels?

Want to know more than your doctor about chronic fatigue syndrome and energy production? Click here.


Originally published at Fatigue to Flourish.