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Why Am I So Tired After I Eat? The Culprits May Surprise You

Feeling tired after eating could be a function of your circadian rhythm and sleep debt, not your diet.
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Woman feeling tired after eating

If you often feel tired after you eat, you may automatically wonder if the food is to blame. Several things relating to your meals can influence that overall feeling of tiredness, including your carbohydrate consumption and consumption of tryptophan. In fact, many people assume the afternoon slump is driven by the increase in blood sugar that can occur after lunch—and the corresponding crash that occurs a short time later when your blood glucose levels fall.

Before you jump to the conclusion that your diet is to blame, however, make sure you take a look at the other factors that could impact your energy levels around mealtimes, particularly after lunch—most notably, your natural circadian rhythm and your overall sleep debt. Sleep debt occurs when you fail to get adequate sleep at night, often on a regular basis. If you aren't getting enough sleep at night, it will downgrade your overall energy potential each day.

In this post, you'll learn more about common explanations for post-meal tiredness, how your circadian rhythm and sleep debt can influence the tiredness you feel throughout the day, and how to determine the answer to “why am I so tired after I eat.”

Common Explanations for Post-Meal Tiredness

There are a variety of things that often get blamed for post-meal tiredness. When you eat, it releases hormones, including cholecystokinin, glucagon, and amylin. Your blood sugar levels rise. Your body produces insulin that helps bring the sugar from your meal into energy that your cells can use for other activities.

If find yourself feeling sleepy after a heavy meal, you may blame:

  • The "crash" that comes after eating sugary foods
  • Consumption of tryptophan, including foods like spinach, eggs, soy, fish, turkey, and cheese
  • A potential medical condition, including hypoglycemia, gluten intolerance, anemia, or even celiac disease

However, in reality, your post-meal slump may have nothing to do with your diet at all. You may make the shift to consuming whole grains, opt for high-protein foods, or transition to a high-fat diet, and track your macronutrients carefully, only to discover that post-meal fatigue has nothing to do with the type of food you choose to consume.

Is It Your Meal, Or Your Circadian Rhythm?

There are three times of the day when your energy is naturally lower and when you’re less likely to feel or function your best:

  • Right after you wake up
  • In the middle of the day, during the "midday dip" or "afternoon slump”: The time will be different based on your chronotype, but for the majority of people—those who are neither extreme early birds nor extreme night owls—the dip hits between 1 and 4 P.M. 
  • As you wind down toward your preferred sleep time/biological night, which usually occurs between 9 P.M. and midnight

It's natural to feel more tired than usual during those times. That's your circadian rhythm—your “internal clock” that determines your natural best wake up time, sleep time, and more—at work. Because you also tend to eat at those points in the day, you may find yourself linking that post-meal sleepiness with a "food coma" or wondering if your post-lunch exhaustion is the result of food allergies, food intolerances, or eating a too-big meal. 

If you're struggling to determine whether sleep debt is to blame for extreme energy dips after your meals, using RISE can help.

RISE app screenshot showing your energy peak and dip times
RISE can not only identify if you’re getting sufficient sleep and how to get more, but also your natural circadian rhythm and the dips that occur throughout the day.

The Importance of Timing Your Meals

When you eat your meals is important for maintaining a healthy circadian rhythm. Meal times serve as cues for your circadian system, which means that if you eat at the wrong time for you, it can actually upset your natural sleep rhythm as well as the times other processes occur in the body. In general, you should avoid eating during your wind-down period—when your body's energy is naturally lower, your metabolism is slower, and your digestive system may operate less efficiently.

During this period, you may crave an increase in glucose to help boost your energy levels but not if you're listening to your body and following its natural flow. The timing and composition of your food choices are important parts of overall sleep hygiene. If you time your meals poorly or if you make poor food choices, you may struggle with a higher sleep debt and lower energy.

Keep in mind that your circadian rhythm is not only unique to you, but it also changes from day to day. It can be influenced by many things, including light exposure, what you eat, and exercise and activity level throughout the day.

The Connection Between Food and Sleep

Food and sleep relate more closely than many people realize. What you consume and when has a substantial impact on your overall sleep, and getting the sleep you need (keeping your sleep debt low) has a significant impact on your diet and metabolism.

Sleeping less than your nightly need can lead to weight gain. Research shows that adolescents who lose sleep by staying up late are more likely to consume high levels of carbohydrates and a higher glycemic load. People who suffer from sleep deprivation are more likely to binge eat, as well as burn fewer calories while awake in their bodies’ attempt to conserve energy.

Likewise, when and what you eat can have an impact on your overall sleep. Eating too close to bedtime has long been known to disturb sleep patterns, which can prevent you from meeting your sleep need. New research shows that eating late may also increase the overall risk of Type 2 diabetes. Eating late at night tends to reduce glucose tolerance and decrease insulin secretion. Taking melatonin supplements too close to eating may have the same effect.

Because food and sleep are so deeply intertwined, it can be difficult to separate them completely. Many people find that in order to improve sleep hygiene, they may need to alter their current diets. What’s more, people who are struggling to maintain a healthy diet and weight may benefit immensely from improving sleep hygiene to keep their sleep debt low.

Determining the Cause of Your Post-Meal Tiredness

If you feel tired throughout the day, in addition to excessive dips in energy during the afternoon slump or after your meals, it could be because you're suffering from an ongoing sleep debt. Getting too little sleep, especially if you're doing things like sleeping for just five hours at night, could, in addition to causing a range of health problems, leave you feeling sleepy after your meal times.

Daily energy is regulated by two critical processes: sleep debt and the circadian rhythm. The lower your sleep debt, the better you will feel and function as you go throughout your day. On the other hand, your energy schedule will naturally wax and wane regardless of how well-rested you are. You will feel your energy peaks more and dips less if you have low overall sleep debt, and you'll notice the peaks less—and struggle more with the dips—when you're struggling with overall sleep debt.

Step One: Inspect Your Sleep Debt

If you're always wondering why am I so tired after I eat, it could be because you're suffering from sleep debt. You suffer from sleep debt when you do not get adequate sleep at night. While eight hours is purported to be the standard for a good night’s sleep, the truth is, your sleep need is unique to you. While the average person needs around 8 hours and 10 minutes, give or take around 44 minutes, 1 in 7 people may require nine or more hours of sleep in order to feel fully rested.

RISE app telling you your individual sleep need and sleep debt
RISE can tell you your individual sleep need and how much debt you have.

Step Two: Identify Your Unique Peaks and Dips in Energy

After inspecting your sleep debt, you can use RISE to identify your natural peaks and dips in energy throughout the day. Eat your meals outside your natural dips in energy to determine whether it’s your food or your circadian rhythm—and, as mentioned above, you should most definitely avoid eating during the third dip right before bed. By shifting your eating schedule, you may be better able to determine whether you're tired because of your circadian rhythm and/or high sleep debt, or if your food is the more likely culprit.

Step Three: Consider Circadian Misalignment

If you find that you're tired after eating, but your sleep debt is low, circadian misalignment could be to blame—most commonly in the form of social jetlag. Social jetlag occurs when your natural circadian rhythm, or biological time, is different from your social clock. You may be struggling with irregular sleep times, or you might simply be operating on a schedule that is entirely out of alignment with your biological needs. Realigning your schedule with your natural circadian rhythm can help reduce tiredness and give you the extra energy you've been looking for.

Step Four: Inspect Your Food

Your sleep debt is low. You're in circadian alignment. Why are you still feeling tired? Now we know with more certainty that your food debt could be to blame. High-carb meals can spike your blood sugar and lead to a crash after you eat. You may want to try:

  • Consuming lower-carb meals
  • Focusing on healthy fats
  • Consuming high-protein meals
  • Consuming smaller meals
  • Eating your large meal early in the day, rather than at the end of the day

There is also a small chance that if you have checked your circadian rhythm, your sleep debt, and your diet, and you are still struggling with feeling tired after a meal, you have a health problem that is to blame. See your doctor or dietitian to rule out any underlying conditions that could be to blame for your post-meal tiredness.

RISE Can Help You Address the Afternoon Slump

Are you still wondering, "Why am I so tired after I eat?" If you need to improve your energy levels throughout the day, start by using RISE to track your natural circadian rhythm and sleep debt. By identifying your natural sleep patterns, you can start to adapt your daily life to take those needs into account and decrease your sleep debt to improve your energy levels. You’ll find RISE gives you the tools to better manage your energy, no matter what type of food you ate for lunch. 

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Rise is the only app that unlocks the real-world benefits of better sleep.

Instead of just promising a better night, we use 100 years of sleep science to help you pay down sleep debt and take advantage of your circadian rhythm to be your best.

Over the past decade, we've helped professional athletes, startups, and Fortune 500s improve their sleep to measurably win more in the real-world scenarios that matter most.

Rise Science is backed by True Ventures, Freestyle Capital, and High Alpha; investors behind category winners Fitbit, Peloton, and Salesforce Marketing Cloud.
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