How sugar makes us tired

Although a sugary snack may quickly produce an energy boost, this feeling won’t last long. An hour later we will feel tired again. It is remarkable how much impact refined sugar has on our energy level and our mood.

“Sugar makes us eat even more sugar!”

Of course, it is commonly known that sugar isn’t healthy, but I must admit, that I love chocolate and ‘dropjes’ (typical Dutch licorice candy). Once I start snacking, I simply can’t control myself. Before I know it, the whole chocolate bar or bag of candies have disappeared. 

What happens inside our bodies?

After consumption, the sugar enters our blood within a few minutes. As soon as our blood sugar level rises, we will rapidly notice a peak of energy. The pancreas will produce an insulin spike, which allows the sugars to easily get absorbed by our body cells. After that our blood sugar levels quickly drop again and we will notice an energy dip, which will make us feel like taking another snack to recharge.

Sugar has a major impact on our energy level

Refined sugars will cause a high energy peak right after consumption but also cause an energy dip very shortly after. The vicious circle of energy highs and lows, make us feel tired at the end of the day. This may even stop us from doing our workouts, with gaining body weight as a result. 

Zero-Sugar challenge

I put it to a test and performed a 30-day zero-(refined)-sugar challenge, with three healthy main meals per day and no snacks in between. I checked every food packaging to ensure the product contained no (hidden) sugars, and I chose mostly fresh food items with healthy fats, protein, and fibers (like  Greek yogurt, with fruits and seeds, or low carb toast with avocado, egg, and tomatoes, fish or poultry, and all kinds of fresh veggies). I wasn’t sure if I would manage the 30 days, but it worked out very well.

No more energy dips

After one week already, I noticed a change. Instead of alternating energy peaks and dips, I felt much more balanced in my energy levels throughout the day. I didn’t yawn once after spending hours non-stop at my laptop. Without any sugary snacks in between the main meals, I was able to stay focused and I was more productive. And I felt like i slept better at night as well.

“No sugar = no dip!”


Stay energized all day!

The goal is to keep our energy levels balanced throughout the whole day. We don’t want to experience an after-lunch energy dip (that causes a snack attack), do we? And after a full day of work, we would like to be still energized enough to spend some active time with our families and friends, or go for a run as well!

Fuel for energy production

Roughly speaking, we have two types of macronutrients to fuel ourselves for energy production:

  • energy-efficient fats, and
  • energy-fast sugars. 

Proteins have other, more important jobs to fill, instead of being used as an energy source. Protein is important for building muscles and producing protein-based substances to assist muscle function.

Energy-efficient fats

We all have more than enough energy-efficient fats stored in our bodies to provide us with energy for weeks while we are at rest. On a duration run, we can make use of fats for hours. 

Sugar for rapid energy needs 

When our body burns sugars it will result in a rapid energy spike, but it won’t last long. For example when we want to lift something heavy or perform a fast sprint. We have far fewer stocks of energy-fast sugars than fat, which means we won’t be able to perform such physical activities for a long time.

Brain function

Our brains only function on sugar, not on fats. Even at rest, our brains need sugars. So if our blood sugar values drop, and we run out of our sugar storage (because our bodies used up the sugars for other reasons), our brain will be the first to get into trouble. Sugar has a bad influence on concentration and creativity.

Sugar is ‘toxic’ to our whole system!

I have noticed that on a day that I consume a lot of sugars, I feel less energized to get things done for work, I easily lose concentration, and at the end of the day, I feel exhausted. The scheduled duration run, then it will probably not go smoothly either.


We have more than enough energy-efficient fat stored in our bodies, so we have to make sure it will be our primary energy source! If we manage to do that, we will prevent an energy dip as well. 

  • Minimize sugar intake: If you can’t resist the urge to refuel a bit, and you really need a snack, then you’d rather choose a handful of nuts  (which contain healthy fats) instead of a sugary snack bar.
  • Eat less frequently to stay energized:  Instead of having smaller snack moments several times per day, you’re better off sticking to three healthy main meals that will keep you saturated until the next meal.

  • Go for a run on an empty stomach (sometimes):  We have enough body fat to provide energy! It’s just that sugars are the easiest way to produce energy, so we need to guide our body towards the fat burn. 
  • Run slower and burn fats: Train more energy-efficient and determine your Heart Rate zones.  HR-zone 3 relates to a fat-burning running intensity at a low/moderate pace. Not only will this increase the duration of your run, but it will also help you shredding some pounds (which makes the next run lighter).

I hope this article has inspired you to minimize sugar intakes and cut out sweet snacks from your daily diet. If you prevent the spikes in your blood sugar, you will recognize that not only your physical and mental energy level remain more stable, but you’ll find yourself in a better mood too!

If you have any questions, please don’t hesitate to contact me at or leave your comment below. If you like this post, please give it a Thumbs-Up and Share it by hitting the social media buttons. Thank you!

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2 years ago

Very nice article! I’ll try to lower sugar consume as much as I can.

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