It’s 2pm, you’re sitting at your desk with a full stomach, and you feel your eyes fall heavy. You feel overwhelmingly sleepy and distracted but it feels like there’s no fighting it. Your lunch is finally catching up to you, and you’ve got the post-lunch slump. But why do you get so tired after eating?
Is it normal to feel so tired after eating?
Yes, relax, It’s a normal response. Getting tired after eating, or “postprandial fatigue” (aka “postprandial somnolence”), is a normal fatigue response to eating a large meal. It’s so normal that the word “food coma” is a huge hashtag on Instagram filled with photo-worthy stomach-filling meals. “Food comas” are among the same family as the “meat sweats” which also have a scientific reason behind them.
Reasons why it happens: 'Fight or Flight' or 'Rest and Digest'
You’ve probably heard about the stress response: “fight or flight” especially when it comes to scary things like fighting a bully on the playground, or standing up and giving a big presentation. You might have felt butterflies in your stomach, or started sweating and turning white - these are the involuntary signs of your nervous system at work. This kind of response is thanks to the sympathetic and parasympathetic nervous system which controls things that you don’t have to tell your body to do - thankfully - like breathe, digest, and make your heart beat.
The parasympathetic nervous system
The involuntary rest and digest portion of the nervous system. Filling up your bladder (thankfully not emptying it) is done without you knowing it, until those stretch muscles send an impulse that gets you on the path to find a restroom nearby. The parasympathetic nervous system also controls digestion - from the secretion of gastric juices and moving contents down the digestive tract. The same goes for sleep.
The sympathetic nervous system
This system is in charge of all the things that get your body ready for activity. It increases your heart rate and decreases blood flow away from non-essential organs. For example, If, hypothetically, you were running away from a threat, you wouldn’t need to spend any extra blood digesting your last meal - you would instead need it to to flow into your muscles to run away and survive!
Actually consuming a meal
Our parasympathetic nervous system kicks in without us having to do anything, and it assumes you’re in a state of rest while you digest the meal. Blood is sent to the digestive system to help digest the meal and send it through your GI tract. Your digestive system normally gets 20-25% of your blood pumped from the heart, but it can almost double when it’s working hard to digest a meal! No wonder you can feel less like taking a run, and more like taking a nap!
You might have heard about your own internal clock that’s typically set to a 24-hour time period - aka, your circadian rhythm. This internal clock helps regulate your body’s natural sleep and wake cycle. Naturally, humans get sleepy around the 2-3pm hour, typically after eating lunch. This is a natural dip in our rhythm, that correlates with natural peaks and valleys of sleepiness, attention span, and alertness.
According to sleep expert Michael J. Breus, PhD: "Right before you go to sleep at night, your core temperature begins to drop, which is a signal to the brain to release melatonin. The exact same thing happens on a smaller scale between 2pm and 4pm in the afternoon. It's a mini-signal to your brain to get sleepy."
While there are natural systems at work after you eat any meal, it’s important to understand the impact of what you are eating as well.
Eating a meal that’s carbohydrate heavy can lead to your insulin rising, which might cause several metabolic changes in your body, hindering alertness and performance.
When is fatigue after eating a concern?
While it may be natural to have a dip in energy in the afternoon after a meal, feeling chronically tired, or tired before and after food, may signal something more.
Here are some potential causes of chronic fatigue after eating:
Chronic lack of sleep
If you’re constantly tired, take note of your sleep patterns, and even consider a sleep journal. In the long run, chronic lack of sleep/sleep restriction can change glucose metabolism and increase insulin resistance which can lead to obesity and diabetes.
Circadian rhythm disorder
If you have daytime sleepiness, along with decreased cognitive performance, difficulty concentrating, along with problems falling asleep - you may have a circadian rhythm disorder.
This can often be due to something temporary like jet lag, or dealing with a new baby that doesn’t sleep through the night. Or it can be something like sleep shift disorders, where working overnight regularly goes against the natural circadian rhythm and conflicts with your own internal clock. According to sleepassociation.org, other circadian rhythm disorders are delayed sleep phase syndrome, advanced sleep phase disorder, or non-24 hour sleep-wake disorder, often found in those individuals who are blind. These can be controlled with therapy and medications, and advice from a sleep professional.
Blood glucose problems
If it’s an issue with low blood sugar after a meal, it might be reactive hypoglycemia. Reactive hypoglycemia is the result of too much insulin produced and released by the pancreas following a meal, particularly a carb-heavy meal. Along with fatigue, it can also cause pale skin, weakness, shakiness, sweating, lightheadedness, anxiety, and confusion. It usually occurs within 4 hours after a meal.
The cause of reactive hypoglycemia isn’t well understood, but checking for underlying medical conditions should be first considered. A balanced diet and eating small meals and snacks throughout the day might help.
If you feel like there is one specific type of food that causes this fatigue or lethargy, it’s time to look deeper into your eating habits. Consider a food diary over the span of a few weeks. Note if there is any particular food or ingredient that causes fatigue after meals. Consider getting tested for food allergies or explore an elimination diet for food sensitivities.
The release of histamines from your allergens could be causing this type of daytime sleepiness that correlates directly to what you’ve been eating for lunch! These issues may cause “brain fog”, a type of mental fatigue, physical tiredness, or digestive upset.
How to stop feeling tired after eating
You don’t have to let your lunch dictate how your afternoon will go! Here are some helpful tips to fight afternoon post-meal fatigue:
Practice good sleep hygiene
Most adults need 7-9 hours of sleep a night to perform at their cognitive and physiological best. It might be normal to get a bad night’s sleep every now and then, but if it’s happening on a regular basis it’s time to brush up on your sleep hygiene!
Limit lights from electronics at least two hours before bedtime as it stimulates the brain, keeping you awake. Dim any room lights at night to prepare your body to sleep. Avoid bright lighting before bedtime, and keep the bedroom dark.
Balance your meals
If a large lunchtime meal is causing the post-lunch slump, try eating smaller meals, and snacks spread throughout the day. But it’s not about nixing all carbohydrates. Tayler Silfverduk RDN, the Celiac Dietitian, gave us some advice for balancing out your meals to limit post-meal fatigue:
“Carbohydrates have gotten a bad reputation lately but they are your body's preferred energy source. Carbohydrates are generally quickly digested/absorbed into glucose (or energy). This raises your blood sugar and thus, energy. However, because they are so quickly digested and absorbed, your blood sugar will also fall quickly leading you to potentially feel fatigued. By adding a balance of protein and fat to your meals, you're slowing down how fast the carbs are hitting your bloodstream, so it's not as big of a spike in energy. Instead, it's more of a slower release of energy, preventing that "crashing" feeling after meals.”
Limit alcohol and caffeine
If you’re having a cocktail at lunch or during the afternoon, consider skipping alcohol use during the day. While it may be tempting to curb the afternoon slump with lots of caffeine, it might backfire on you that night! Limit caffeine during the afternoon hours if you are sensitive to it affecting your sleep habits at night.
Drink more water
Dehydration can add to fatigue that you might already be experiencing in the afternoon. If you’re not a fan of drinking plain water, try incorporating more water-filled food into your lunch meal like fruits, vegetables, skim/soy milk and soups.
Get up and get moving
When you feel your energy levels starting to dip, take a walk! Not only will exercise get the blood flowing to your extremities and help energize you, but it also improves digestion and helps reduce blood sugar levels. Plus if you’re exercising outdoors, the light from the sun will naturally help you feel more energized with bright light and UV exposure and deliver a bonus of some vitamin D!
Try bright light
An exposure to blue, bright light, especially combined with caffeine, can be a way to get energized and fight the natural afternoon slump. If you really want to maximize bright light, combine it with a short nap and caffeine! So open those windows in your office or get outside to get energized.
If you feel tired or lethargic after a meal there’s a very good chance it is entirely in response to the chemical changes that occur during digestion meaning; it’s totally normal. If your fatigue symptoms are very disruptive, appear to be worsening or don’t change after experimenting with the above suggestions, speak to your physician.