Quentin McCree
Article by: Quentin McCree
Estimated 11 minutes read

Many people experience a noticeable drop in energy levels after consuming sugary foods. This phenomenon can be puzzling, as sugar is a fundamental energy source for the body's cells. In this article, we explain why sugar makes you tired, the underlying causes of tiredness after eating, and the specific effects of fatigue after sugar consumption.

Structural chemical formula of glucose with refined crystalline sugar and cube sugar

Understanding the Basics: Sugar and Energy

Sugar - in the form of glucose - is the primary fuel that powers human cells. Under normal circumstances, consuming sugar raises blood glucose levels, prompting the pancreas to release insulin. 

This molecule helps cells absorb glucose, either to use as energy or to store it in the form of glycogen. However, this process can sometimes lead to fluctuations in energy levels, particularly when it involves refined sugars. 

Immediate Energy High and Subsequent Crash

One of the main reasons sugar makes you tired is the initial energy boost experienced after consuming sugar. This is due to the rapid absorption of sugar into the bloodstream, leading to a quick spike in blood glucose. 

This spike prompts a corresponding surge in insulin production to help cells take in glucose, potentially leading to an overcorrection that reduces blood glucose levels too much, a state known as hypoglycemia. 

This sudden drop in blood glucose often results in fatigue after sugar intake.

The Role of Insulin in Sugar-Induced Fatigue

Insulin plays a pivotal role in regulating sugar. An excessive increase in insulin can drive blood glucose levels down, leading to tiredness and lethargy. 

This response can be more severe in individuals who are sensitive to insulin or who experience inefficient glycemic regulation, such as those with diabetes or prediabetes.

Glycemic Index and Sugar Fatigue

A food's glycemic index (GI) indicates how quickly carbohydrate-containing foods increase blood glucose levels. Foods with a high GI, including many processed sugars and sweets, can cause rapid spikes and subsequent drops in blood glucose levels. This rollercoaster-like fluctuation is a key cause of tiredness after eating sugary foods.

Inflammation and Immune Response to High Sugar Intake

Consuming large amounts of sugar can increase inflammatory markers. Sugar prompts the release of inflammatory cytokines, signaling molecules that mediate and regulate immunity, inflammation, and hematopoiesis. This inflammatory response can contribute to fatigue as the body manages the inflammation.

Impact on Serotonin Levels

Sugar can also influence fatigue through its effects on serotonin, a neurotransmitter that helps regulate mood, appetite, and sleep. Interestingly, consuming sugar increases serotonin production, which, although initially leading to feelings of well-being, can also promote sleepiness and lower energy levels, particularly if sugar consumption occurs in large amounts or without accompanying proteins or fats to stabilize its effects.

Sugar Makes You Tired Due to Digestion and Energy Diversion

Digesting large quantities of sugar requires a significant amount of energy, which can divert resources away from other body functions. When the digestive system is overburdened, the body may reduce energy supplied to muscles and the brain, resulting in tiredness.

Habitual Responses and Conditioned Cycles of Sugar Consumption

For some, the fatigue after sugar intake may also be linked to conditioned behaviors or psychological responses. Regular consumption of large quantities of sugar can lead to a cycle of short energy spikes followed by a crash, which affects physical energy levels and conditions the body to experience a downturn in energy after sugar intake.

Emotive dark skinned bearded guy keeps both hands on head, opens mouth from surprisement as sees too much desserts at one table

What is Sugar Addiction? 

The concept of sugar addiction involves a cycle where consuming sugar-rich and fatty foods triggers the release of dopamine and naturally occurring opioids in the brain. This biochemical reaction enhances the pleasure of eating such foods, reinforcing the behavior and increasing the likelihood of cravings. 

Over time, this repeated cycle can make sugar seem like a reward to the brain, leading to a dependency that is both neurochemical and behavioral. That's why reducing sugar intake can be challenging for many individuals.

Key Reasons Why Sugar Makes You Tired

It's normal to feel lazy after eating something sweet. Here are a few reasons behind the tiredness you feel after consuming sugar. 

  • Blood Sugar Spikes and Crashes: Consuming simple carbohydrates, like those found in sugary snacks, can cause immediate rises in blood sugar levels followed by sharp drops. This is because the body releases insulin to help absorb the glucose into the cells, and an overabundance can lead to a sudden decrease in blood glucose, which may result in tiredness.
  • Effects on Sleep: Regular consumption of high sugar levels can negatively impact your sleep quality and duration. Poor sleep, in turn, contributes to daytime tiredness. Studies have shown that higher sugar intake can disrupt sleep patterns, making falling and staying asleep harder.
  • Orexin Suppression: Sugar impacts the orexin system in your brain, which plays a key role in keeping you awake and regulating your energy levels. High sugar intake has been shown to reduce the activity of orexin-producing neurons, leading to increased feelings of sleepiness.
  • Dietary Impact: Foods high in sugar often lack fiber, protein, and healthy fats, crucial for sustained energy levels. Consuming meals balanced with these nutrients can help stabilize blood sugar levels and prevent the fatigue associated with sugar consumption.

How to Prevent Tiredness After Consuming Sugar? 

To help your body process sugar more efficiently, consider taking your desserts with foods high in protein or fat. This slows the absorption of sugar into the bloodstream. 

Additionally, consuming candies, sugary drinks, and desserts after a meal rather than on an empty stomach can help mitigate feelings of fatigue. Reducing your overall sugar intake will prevent unwanted energy slumps. Consult your doctor to check your blood sugar levels if you frequently feel tired after consuming sugar.

Tips to Prevent Fatigue After Sugar Consumption

Here are some tips that can help you prevent tiredness after consuming sugar. 

1. Combine Sugar with Protein 

Add protein to mitigate the tiring effects of sugar. Opt for protein desserts, such as cheesecake or peanut butter treats, or have a protein-rich snack like nuts or meat before eating sweets.

2. Combine Fats with Sweets 

Include fats in your desserts to improve sugar metabolization in the body. For instance, combining fatty foods like nuts and sweet fruits can stabilize energy levels. If you often feel tired after having a fruit smoothie, try snacking on a handful of almonds just before.

3. Avoid Sugary Snacks On Empty Stomach 

Instead of consuming sugary snacks on an empty stomach, consume them as a dessert after meals. Eating sugary items on an empty stomach can lead to sleepiness and lethargy. If you typically have sugary treats in the mid-afternoon, try to enjoy them post-meal, which can help maintain stable blood sugar levels.

4. Steer Clear of Sugary, Caffeinated Beverages

Avoid beverages that mix sugar and caffeine, such as sweetened tea and coffee, sodas, and energy drinks. While these might initially boost your energy, the sugar-caffeine combo leads to a subsequent crash, leaving you feeling down. When you need a caffeine boost, choose flavored sparkling water, lightly sweetened tea, or plain black coffee.

5. Cut Down on Your Sugar Intake

Feeling sleepy after eating sweets may indicate that you're consuming too much sugar. Adhere to official dietary recommendations, such as those from the U.S. Department of Agriculture, which suggest that only 10% of your daily calories should come from sugar.

On a 2000-calorie diet, only 200 calories should be sugar-based. Consider substituting sugary beverages with unsweetened teas and choosing low-sugar fruits, like berries, instead of candies.

6. Monitor Your Sugar Intake 

Many processed items, including salad dressings and yogurt, can have high added sugars. It can undermine your efforts to reduce sugar consumption. Be vigilant and read the labels at stores. Refined sugar may be listed under many names, such as:

  • Glucose
  • High-fructose corn syrup
  • Honey
  • Lactose
  • Brown sugar
  • Corn sweetener
  • Corn syrup
  • Dextrose
  • Maltose
  • Molasses
  • Raw sugar
  • Sucrose
  • Fructose
  • Malt syrup

If you see any of these items listed in the ingredients of a processed good, be aware that they are rich in refined sugar.  

7. Consult Your Doctor 

Feeling sleepy after consuming sweets might indicate a deeper health concern. If you regularly experience fatigue following sugar intake, visit your healthcare provider. They may run blood tests to check if your blood sugar levels are within normal ranges and offer guidance on regulating sugar in your diet. 

8. Stay Active

If you start feeling drowsy after eating sweets, consider exercising. Whether it's a light stroll or an intense workout, physical activity can revitalize you. If a sugary snack in the afternoon makes you sluggish, try walking around your office to energize yourself.

Does Feeling Tired After Consuming Sugar Indicate Diabetes?

Feeling sleepy after a meal might seem like a natural response to feeling full and satisfied, but sometimes, it could point to an underlying health issue such as type 2 diabetes. 

Type 2 diabetes is a chronic condition where the body struggles with insulin resistance or insufficient insulin production, leading to abnormal blood sugar levels in the bloodstream.

Insulin and Blood Sugar Dynamics

Insulin is a crucial hormone produced by the pancreas. Its primary role is to manage blood sugar levels by facilitating the entry of glucose into the body's cells to be used as energy. 

When the body becomes resistant to insulin or insufficient insulin is produced, glucose accumulates in the bloodstream instead of being utilized by the cells. 

This imbalance can cause various health complications over time, including heart disease, kidney damage, nerve problems, and impaired vision.

Why Does Diabetes Cause Sleepiness After Meals?

In individuals with diabetes, sleepiness after eating can occur due to either high blood sugar (hyperglycemia) or low blood sugar (hypoglycemia). 

Hyperglycemia happens when there's too much glucose in the blood, whereas hypoglycemia occurs when glucose levels drop too low. Both conditions can trigger a sense of fatigue or sleepiness as the body struggles to maintain normal energy levels.

Is It Always Diabetes?

While post-meal drowsiness can be a sign of diabetes, it's not a definitive symptom on its own. Many people experience a natural dip in energy after eating, particularly after a large meal or one high in carbohydrates and fats, which requires more energy to digest. This response is often referred to as "food coma" or postprandial somnolence and is quite common.

If you frequently feel sleepy after meals, and this is coupled with other symptoms like frequent urination, intense thirst, blurry vision, or unexplained weight loss, it might be wise to consult a healthcare provider. 

Other factors that can lead to glucose intolerance and its potential consequences are:

  • Poor Night Sleep

Sleep issues can make you feel tired after meals and throughout the day. It's crucial to adopt good sleep habits by sticking to a consistent bedtime routine and avoiding caffeine, alcohol, or screen at least 4-6 hours before bedtime. These steps can help improve your overall sleep quality and reduce daytime fatigue.

  • Sedentary Lifestyle 

No physical activity post meals can make you feel tired, which can intensify after you eat. When you don't get regular physical activity, your digestive, cardiovascular, and musculoskeletal systems do not function efficiently. These issues collectively contribute to increased fatigue.

Regular exercise boosts energy levels consistently throughout the day. Being active can also help reduce the sleepiness you might feel after meals.

  • Poor Diet

Certain foods, particularly those high in carbohydrates and fats, can tire you. Moreover, certain foods increase the production of serotonin - a chemical that helps produce melatonin - which induces sleep.  

Foods That May Cause Tiredness

Here's a list of foods rich in fats and carbohydrates that might make you drowsy after eating:

  • Cakes, donuts, muffins, and cookies
  • Sugar, including candy
  • Poultry
  • Cheese
  • Milk
  • Rice
  • Pasta
  • White bread
  • Soy products
  • Seeds
  • Salmon
  • Eggs

The portion size also matters. Overeating, especially during lunch or dinner, can spike blood sugar, leading to feeling drowsy.

What Can Cause Diabetes? 

There is a close link between diabetes and thyroid diseases. When you have hyperthyroidism, the insulin levels drop, and blood sugar rises. It increases the risk of diabetes. Check out the early warning signs of thyroid problems.  

Secondly, too much and too little cortisol seriously affects hormones and can cause diabetes. Cortisol raises blood sugar. If you have chronically high cortisol levels, they can lead to persistent high blood sugar (hyperglycemia), which can cause Type 2 diabetes.

Diet and exercise play a key role in creating visceral fat. A diet with a high intake of carbohydrates (sugar) and fatty foods provides building blocks that increase visceral fat. This belly fat is dangerous. The excess of sugar building in the blood can lead to diabetes. 

Conclusion: Why Sugar Makes You Tired

Feeling tired after eating sugar is influenced by various physiological processes, from blood sugar regulation to inflammatory responses and serotonin production. By understanding these mechanisms and adjusting dietary habits, individuals can better manage their energy levels and mitigate the sluggish effects of sugar.

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