Why Do I Feel Tired After Eating Sugar?

What people call a sugar crash

You eat something sweet, feel a quick boost, and then an hour or two later you’re tired, a bit foggy or hungry again. That pattern is often called a sugar crash.

When you eat sugar or other fast-digesting carbohydrates, your blood sugar rises, and your body releases insulin to bring it back down. For some people, that swing is followed by a dip in energy and mood. Scientists are still working out exactly how much of the effect comes from blood sugar itself and how much from other things, like sleep, stress and what else was on the plate.

What research says

A 2019 review in Neuroscience & Biobehavioral Reviews pooled the results of many studies on carbohydrates and mood. It found that people did not generally feel better after eating carbohydrates, and that within about an hour they tended to report more tiredness and less alertness. So the idea that sugar gives you lasting energy isn’t well supported, although people react differently and the studies can’t tell us exactly why.

It’s also worth saying what we don’t know. Most studies are short, and your own pattern depends on your meal, your sleep and your body.

What tends to help

• Eat sweets with food, not alone. Having dessert after a meal that includes protein, fiber or healthy fat usually gives a gentler rise than a sweet snack on an empty stomach.
• Add something that slows it down. Fruit with nuts or yogurt does more for you than fruit juice on its own.
• Move a little. A 10-minute walk after eating can help you feel more awake.
• Protect your sleep. Tired days make cravings louder and sugar feel more necessary.
• Notice the timing. If the dip always comes mid-afternoon, plan a steadier snack for around then.

Try this today

Next time you have something sweet, write down the time and how you feel 30 minutes and 90 minutes later. A few notes will show you whether sugar really gives you a lift, or just a loan.

FAQs

Is a sugar crash the same as low blood sugar?

Not always. Feeling tired after sweets is common and usually mild. True low blood sugar can cause shakiness, sweating and confusion, and needs proper medical attention.

Does everyone crash after sugar?

No. Some people barely notice it and others feel it strongly. Your meal, sleep, stress and health all play a part.

When should I talk to a doctor?

If you often feel shaky, dizzy, faint or confused after eating, or if you have diabetes and notice big swings, please speak to a doctor.

Feel an afternoon dip? Share what helps you in the Sugar Control Circle on Facebook.

This article is for general wellness and isn’t medical advice.

Sources: Neuroscience & Biobehavioral Reviews (2019): Sugar rush or sugar crash? A meta-analysis of carbohydrate effects on mood