The Dark Side of Fasting – How to Avoid the Negative Side Effects of Intermittent Fasting

Siim Land

What are the negative side effects of intermittent fasting? There are many. This article helps you to find and avoid them.

The Negative Side Effects of Intermittent Fasting

Woohoo! Intermittent fasting’s great and incredibly healthy. I’ve been doing it ever since high school and my fat-adaption is quite effective. It’s highly effective…

Looking back on my journey, I can’t say it’s been super-duper all along. My IF has lasted for so long that I sometimes forget that fasting has its downside.

Of course, the first days will be dreadful if you’re not used to it. But even now I can’t escape some of the negative side-effects and slippery slopes that make me fall into darkness.

We’re in the Underworld now – the Dark Side of Fasting no one talks about.

Hypoglycemia While Fasting

When you’re starting to do intermittent fasting, your body isn’t that used to going without food for any longer than 12 hours. Even though you’re carrying around a ton of calories in your body fat, you’ll still have low energy, experience exhaustion, dizziness, and low blood sugar levels.

Hypoglycemia is uncomfortable and can actually be dangerous. It’s caused by inadequate amounts of glucose in the blood stream, which starves your brain from energy. #shutdown #blue-screen-of-death

What to do about it?

You shouldn’t expect to be full of energy when adapting to this and instead take things slowly.

  • Rest during your fasting window and avoid extremely strenuous physical activity.¬†For now…
  • Drink more water to prevent hunger and additional stress
  • Consume more electrolytes and sodium in your food and water
  • Lower your carbohydrate intake to transition over from a sugar burning engine to a fat-adapted metabolism

The reason you feel hypoglycemia is because your body is running on glucose, but because there are no carbs to be found, you undergo an energy crisis.

Muscle Loss While Fasting

Sugar burning again.

In general, fasting doesn’t burn muscle mass. In fact, human growth hormone and ketones are protein sparing, which preserve lean tissue at the expense of increased fat burning. However, initial periods of fasting can be characterized by higher rates of gluconeogenesis, especially if you’re doing it on a diet with a lot of carbs.

What to do to not lose muscle while fasting? Same – rest and sodium.

Training in a fasted state will actually cause a greater anabolic response once you start eating again. And you can easily build muscle that way, as long as you get enough protein and calories.

That’s why avoiding a caloric deficit is a good idea. Eat at maintenance when you’re trying to get used to fasting and start eating more fat instead of carbs. After you’ve done IF for a few weeks, you can fast without losing any significant muscle.

Drop in Mood

Although you’re completely mentally clear and sharp, you can still become a person who you don’t want to be around. Moodiness, grumpiness, avoidance, lethargy, exhaustion, snappiness can all be the negative side effects of fasting.

What to do? – A warm cup of coffee gives you energy and livens up the heart. The caffeine will increase fat oxidation and releases adrenaline, which remove the clouds of mental fog.

Also, you can break your fast and eat something before or during social interactions.

Digestion Issues

Both constipation and diarrhea can be an issue. Your body will begin to strike back after you get used to fasting. This is only temporary and becomes less of an issue after a few days.

  • If you feel constipated and haven’t had bowel movements in days, then drink more water, some apple cider vinegar, add more fiber into your meals, consume more potassium, and electrolytes again.
  • If you get uncontrollable disaster pants after you break your fast, then eat some charcoal tablets and herbal teas.

Weight Loss With Intermittent Fasting

Some people say they can’t do IF because they simply aren’t capable of cramming their calories into a restricted eating window. If they have to eat 3000 calories, then that’s a lot of food to consume between 4-8 hours. ¬†Especially, if you’re eating whole foods.

The solution here is simple again. You can either shorten your fasting just a bit or reduce your activity levels. You don’t have to do hours of cardio just to burn fat if you already can’t eat your calories for recovery. Don’t exercise just to eat more. Eat so you could achieve your training goals.

Also, you’ll get used to eating larger meals with IF as well. When you’re fasting, your body adapts to burning its own fat for fuel and when you start feasting, you’ll digest the food quicker as well, because your body wants to supercompensate for the abstinence.

Binge Eating

Now, this is a real issue.

Some people can’t stop eating. During the fast they’re perfectly fine – they could continue fasting for days without losing their mind – but once they start feeding, they just gorge themselves and eat and eat and eat until they can’t move anymore.

This tends to happen in the first few days. SOOO HUNGRY! You eat your first meal, then you come up with random food combinations and add sugar and fats together, all types of sauces on everything and other insanities of hunger.

What you need is self-control and mindful eating. If you already made through your fast, which is supposed to be the hard part, then you should also have enough discipline to control your urges for longer.

The reason you feel like wanting to eat a horse is caused by your inability to burn fat for fuel yet again. 

People report that after fasting for 3-5 days, they lose their hunger completely and their mind is very clear. It’s because they get into deep ketosis, even if they normally eat a carb unrestricted diet. If you were to do intermittent fasting on a ketogenic diet, you’ll have energy and reduced appetite straight from day 1.

Decreased Metabolic Rate

And the biggest negative side effect of intermittent fasting is that your metabolism gets sluggish and slows down.

Don’t take this the wrong way – skipping meals and intermittent fasting doesn’t slow down your metabolism and make you fat. Your body is an adaptive machine and it’s not going to store all your food as fat after you start eating. In fact, fasting for 48-hours can increase metabolic rate by up to 14%.

The problem is that fasting is still a stressor to the body – elevated cortisol and adrenaline levels can wreak havoc to your hormones and metabolism if they cause too much stress.

Adrenal Fatigue Because of Fasting

If you’re doing intermittent fasting, have a ton of work to do, you’re screaming at people, have negative self-talk, workout 3 hours a day, watch blue screens all day and can’t sleep, then you’re asking for trouble.

Being constantly stressed out will lower testosterone, makes you hold onto fat, causes diabetes, insulin resistance and leads to adrenal fatigue. You have to chill the fuck out, before you burn the fuck out.

To avoid it, you shouldn’t fast for too long too frequently. If you’re already fasting for 16 hours every day, then you don’t need to add an additional stressor to your body by having another 3 day fast every month. Fasting is great but the key is to do it intermittently. Eating is still needed and good for you.

Micronutrient Deficiencies

In a similar vein, you can eventually get some micronutrient and mineral deficiencies.

  • If you don’t eat for days, your body won’t have access to some of the essential nutrients it needs for health, such as omega-3s, magnesium, potassium, vitamin B12 and many more.
  • And if you do it, but only in a very restricted time window, like in one hour, you won’t be able to metabolize all those micros.

Whatever the case, to not become deficient, you should prioritize nutrient dense whole foods that have the nutrients we need. Green leafy vegetables, unprocessed meat, fish, eggs, and healthy fats.

Because It’s Worth It

As you can see, it’s not all sunshine and rainbows with intermittent fasting.

Even though it can be uncomfortable sometimes, it’s totally worth it. I mean, your health is better, you’ll live longer, your mind is sharper, no hunger or exhaustion, you can be more creative, productive and you’ll burn fat very easily.

The key is to actually learn how to burn your own body fat for fuel. That’s why your experience with fasting depends on how long you’ve been doing it and what kind of a food you eat during your feasting window.

I myself do the ketogenic diet, which keeps me in a similar state as fasting does. Fasting induces ketosis and the ketogenic diet mimics the physiology of fasting. Keto isn’t the end-all-be-all, and you’ll be fine with just doing intermittent fasting. However, keto makes fasting so easy because you’ll always have energy.

If you’re interested in learning more about the ketogenic diet, then check out my free e-book Simple Keto. And if you want to master the craft by combining it with intermittent fasting, then you need to get my KETO // IF program. It’s a blueprint for becoming insanely fat-adapted.


Stay Empowered