Feeling tired in the afternoon? Here are five possible reasons why

You’ve likely experienced that wave of afternoon sleepiness before; the one that hits between 1 p.m. and 4 p.m. It’s a natural part of your body’s circadian rhythm: the internal clock that regulates sleep, energy, and alertness.¹

But not everyone experiences this afternoon slump the same way. For those who haven’t been getting enough sleep, it can feel like a serious crash in energy and mood, while for others, it can feel like a minor blip in alertness.

A spike in your glucose levels followed by a dip can also lead you to feel drained later in the day.

Although it’s natural to feel a slight energy slump in the afternoon, excessive fatigue may be avoidable. Understanding what's behind your tiredness can help you work out what to do to feel more energized.

If you’re feeling really tired during an afternoon slump, it could be due to one of these factors:

5 possible causes of afternoon tiredness

1. Eating a heavy lunch

A big lunch comprised of foods that score high on the glycemic index (GI) may fill you up, but it won’t do your energy levels any favors.

High-GI foods contain carbohydrates that you digest quickly, which can cause blood glucose and insulin levels to rise. A rapid rise in glucose, or a glucose spike, followed by a crash may lead you to experience feelings of fatigue and overall lower energy.²

Tip for Lingo members:

After eating your lunch, keep an eye on your glucose levels. Look out for a big rise followed by a sharp dip. You may find that the higher your Lingo Count, the more tired you feel afterward.

2. Eating sugary snacks

Reaching for sugary snacks when you’re feeling tired, sluggish, and in need of a boost can make the problem worse.

These quick-fix, ultra-processed foods are packed with simple sugars and refined grains that your body breaks down fast. This can flood your system with glucose, resulting in a glucose spike.  
 
To address the excess glucose, your pancreas releases insulin to help move the glucose to working tissues or place it into storage. As insulin does its job, glucose levels start to fall and you may experience a sharp dip in energy, leaving you feeling tired and craving a quick hit of energy once again.

By eating fewer sugary snacks and keeping your glucose levels more steady, you’re more likely to feel more energetic³ as well as have fewer cravings.⁴

3. Lack of sleep

When you don’t get enough sleep, consistently less than 7 hours a night⁵—you’re likely to feel tired throughout the day.

And when the normal mid-afternoon slump comes around, you might feel it more intensely than someone who is well-rested and getting enough quality sleep

Not getting enough sleep can also lead to poorer glucose control the next day and a bigger glucose response to your breakfast.⁶

Poor sleep is also linked to craving foods that are high in carbs and sugar,⁷ which can lead to glucose spikes and contribute to rises and dips in energy throughout the day.

Learn more about how much sleep you should get.

4. Exercise: too little or too much

While some people might associate physical activity with feeling tired, not getting enough exercise can also have a similar effect.⁸

Exercise is important for your energy levels as it stimulates the production of mitochondria, often referred to as “the powerhouses of the cells.” These small structures are vital for energy production throughout the body.

Physical activity also helps improve your circulation, which helps the mitochondria function efficiently and supports your muscles and organs.

If you feel sleepy in the afternoon, it could be a sign that you’ve either pushed too hard during your morning workout, or that you haven’t properly refueled with enough food and hydration afterward.

Interestingly, while low- to- moderate-intensity exercise (i.e. walking or Hatha-style yoga) can lower your glucose levels, high-intensity exercise (i.e. HIIT or team sports) can cause your glucose to spike.

These exercise-related spikes are good, however, as they reflect your body’s increased demand for energy to fuel its activity.⁹

Learn more about the effect of exercise on your glucose levels.

5. Dehydration

If your body is losing more water than it’s taking in, you may feel tired.

When you’re dehydrated, your blood volume drops, making it harder for oxygen and nutrients to reach your cells. This can leave you feeling sluggish and low on energy.¹⁰

In addition to fatigue, studies show that even mild levels of dehydration can impair cognitive functioning including things like concentration and alertness.¹⁰

Staying hydrated helps your body deliver what your cells need to keep you feeling energized, both mentally and physically.

Impacts of afternoon fatigue

While afternoon sleepiness is common, fatigue can have broader effects, including changes in mood, behavior, and performance.

Here are a few effects to be aware of:

• Lack of concentration. Fatigue can make you less productive, impair performance, and even impact your concentration.¹¹

• Waning exercise motivation. You may feel like making excuses to skip an evening workout when afternoon fatigue hits. But better understanding the root cause of your tiredness can help you adjust your day and preserve the energy needed to stay active. After all, regular exercise helps you feel more energized in general.¹²

• Low mood. Fatigue can make you feel less energetic and lower your mood, especially in the afternoon when sleepiness builds and your body’s alertness naturally dips.¹¹

• Eating the wrong foods for energy. Fatigue can lead to stronger cravings for high-calorie, sugar-dense foods, even when you're not necessarily hungrier.¹³

How to beat an afternoon slump

If you’re often finding yourself yawning mid-afternoon, these steps might help you feel more energized as you move toward the evening:

To stay energized through the day:

• Ensure you’re getting enough quality sleep.

• Try to prioritize low-GI foods to help stabilize glucose levels and prevent food-related energy crashes.

• Exercise regularly, but be sure to rest when your body needs it.

• Hydrate. Though individual needs can vary, adults should aim to drink around 3 liters a day as a minimum.¹⁴

• Limit your afternoon caffeine intake, as having caffeine late in the day can make it harder to fall asleep later on.

Using the Lingo CGM system could help you better understand how different foods and activities influence your unique glucose response and how this might relate to your energy levels. Get real-time glucose data and personal insights that could help you build healthy habits.

Learn more about how to achieve better daily energy levels.

A final note from Lingo

Some degree of afternoon fatigue is natural, but the extent to which you feel exhausted is determined by a variety of factors, including what you’ve been eating and how much rest you’ve been getting.

Lingo is designed to help you see the impact of your eating and exercise habits on your glucose. Use the glucose data it provides to find foods that work for you and make changes that support your health goals.

There are also some health conditions that can cause excessive tiredness and fatigue. If you’re consistently experiencing afternoon sleepiness and don’t think it’s due to any of the factors listed above, it may be worth speaking with a healthcare professional to explore potential underlying causes.

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