Frustrated Feeling Sleepy During the Day? (What Sugar Has to Do With It)

Do you find yourself feeling sleepy during the day, even after a full night’s sleep? You’re not alone. Millions of people struggle with daytime fatigue — and one surprising cause could be sugar.

The following is my personal story of overcoming daytime sleepiness. This is my simplified understanding of what’s happening inside the body. It may not be 100% scientific, but it explains a pattern that made sense for me. At the end, I’ll share a resource from an expert that dives deeper.

There are many reasons why a person might feel tired, but in my experience this is the big one.

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My story of feeling sleepy during the day

When I was in high school in the mid-60s, I was constantly on the verge of falling asleep in class. Even though I slept well at night, I always felt tired during the day.

In year eleven, I had a history class right after lunch that I really enjoyed — but I still couldn’t stay awake. I was always feeling sleepy during the day.

I mentioned that I was feeling sleepy during the day to my dad, and he took me to our family doctor. After hearing my story, the doctor told me I had “low blood sugar.” His advice was simple: eat a candy bar after lunch every day.

I loved candy bars, so I happily followed his advice. The problem was, my sleepiness didn’t improve. In fact, it got worse. So I reasoned I needed even more sugar. I ate plenty — but no matter how much I ate, my sleepiness never went away.

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A surprising discovery

Years later, I was still eating sugar and still feeling sleepy during the day. One day I was at a friend’s house, browsing his bookshelf, and I came across a book called Are You Tired All the Time?

That book changed everything. It explained how sugar can actually make you tired. It described a condition called hypoglycemia (low blood sugar) that produced the same symptoms I had.

My doctor had been correct about the diagnosis — but 100% wrong about the cure.

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How sugar affects your energy

At any time, the body is only supposed to have about one teaspoon of sugar in the blood.

When you eat sugary foods — like a candy bar or soda — it almost instantly dumps several tablespoons of sugar into the bloodstream. The body doesn’t like this overload, so it releases a chemical called insulin.

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The role of insulin

Insulin has two main jobs:

1. Convert sugar into fat
   • Sugar in the blood is quickly turned into fat, because fat can be stored in the body while sugar cannot.
2. Tell cells to absorb sugar
   • Insulin signals millions of cells to open up and take in some of the excess sugar from the blood.

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Why too much sugar makes you tired

These mechanisms are good — but two problems can develop:

• Overreaction to sugar spikes
  Some people (like me) release too much insulin. This clears nearly all the sugar from the blood, and the result is… you guessed it: feeling sleepy during the day.
• Insulin resistance
  Over time, cells become resistant to insulin because they’ve already absorbed too much sugar. The body sees high sugar in the blood and releases even more insulin, but the cells won’t respond. This leaves them without enough fuel — and again, you feel tired.

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Simple lifestyle changes that helped me

The short version? I needed to eat less sugar.

Cutting back on sugar, along with a few other simple lifestyle changes, made a huge difference in my energy levels. If you find yourself nodding off during the day, this might be part of the reason.

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Learn more

👉 Want to dive deeper? Watch this explanation and two short videos by Dr. Berg that explain exactly how sugar impacts energy levels and what you can do to fix it.

You Will QUIT Sugar After Watching This (Guaranteed) – Dr. Berg