food comas energy

Why do we get food comas if food gives us energy?

We’re all aware of the importance of food to keep us supplied with energy, like having a good breakfast, for instance, to get us off to a jumpstart to the day. However, why is it that we often go through food comas, also known as postprandial somnolence, following large meals if calories are supposed to give us energy?

In this Plato Weight Management article, we’ll explain:

  • How food provides you with energy
  • What is sleep
  • Why eating is thought to make you sleepy
  • How to avoid the impact of food comas on energy

How food provides you with energy

food comas energy

There are three nutrients, collectively referred to as macronutrients, from which we obtain energy.

These include carbs, protein, and fat.

When broken down during digestion, their byproducts increase the secretion of hormones such as insulin that helps to initiate the chemical reactions known as metabolism.

Metabolism is important as it helps turn these byproducts into energy that help us with life-requiring tasks, including cell division, nutrient processing, breathing and pumping blood around the body.

Basically, when food enters your body, these nutrients are absorbed into your blood circulation when they reach your stomach and then are processed by the relevant organs further to be absorbed by cells.

Although it’s important to point out that not all macronutrients contain the same number of calories as fat contains nine calories per gram while carbs and protein have four.

Interestingly, some researchers believe that alcohol is also a macronutrient containing seven calories per day.

However, there is some debate regarding if alcohol qualifies as a macronutrient or not.

But what is a calorie anyway?

Well, a calorie is actually not a calorie.

I’ll explain.

The calorie we have become accustomed to is known in nutrition as a kilocalorie, meaning 1000 of even smaller calories. This is why you’ll see kcal beside calories on nutrition labels. 

A kilocalorie is the energy we need to raise 1g of water by 1 degree, also defined as 4.18 kilojoules.

But calories from food aren’t just different because of the variation in calorie content from macronutrients, as you will not consume foods with fat, protein or carbs in isolation. 

This is because there’ll also be some vitamins and minerals in the food, and other macronutrients for that matter too, influencing the digestive effect on calories.

For instance, if you consume candy with a lot of sugar and little vitamins and minerals, you will get a much faster rush of energy than if you were to consume vegetables or whole grains as the energy from these foods is gradually released over the hours following.

To read our blog about why you may not be losing as much weight as you could be, please follow the link here.

What is sleep 

food comas energy

Although there is a lot we are still unsure of when it comes to sleep, it has been found essential to various functions within our body.

These functions include allowing the formation of new pathways in your brain to acquire new skills, remember key events and information, enhance the signalling between neurons in addition to helping to remove waste from your brain.

Also, sleep is crucial because it helps prevent disease, obesity, depression, cardiovascular output, and many others.   

It consists of four stages, with the first three being referred to as non-rapid eye movement sleep, while stage four is known as rapid eye movement sleep.

Stage one is considered light sleep, and sleep becomes deeper with each stage after that.

Why eating is thought to make you sleepy

Rest assured that food comas are not just a figment of your imagination as there is research backing up their existence sapping energy.

For example, Reyner, Wells and Horne found that eating bigger meals before going for a long drive resulted in relevantly more sleepiness than having smaller meals.

Currently, the exact reason why food comas happen is unknown.

However, there are several theories.

In this article, we will discuss the most popular:

The first way that food comas may occur after eating large meals could be due to the endocrine system’s response.

For instance, serotonin, known as both a hormone and a neurotransmitter, is responsible for sleep.

You may have heard of it before as it is also one of the primary hormones, along with dopamine and endorphins, that cause happiness, but has other notable effects outside of sleep regulation and happiness too, such as appetite, learning ability and memory. 

The difference between hormones and neurotransmitters are that while hormones are chemical messages secreted by glands in the endocrine system to control various bodily functions, neurotransmitters are chemicals used by the central nervous system that sends out information to the body.

Interestingly, as much as 95% of the body’s serotonin is found in our stomach and is partially released when food enters the stomach, which may be a further reason why eating a lot can make us feel tired.

Although, it isn’t food directly which causes serotonin production.

Rather it is an amino acid known as tryptophan, which is found in foods rich in protein.

At the same time, carbohydrates may also contribute to tiredness as they assist the body in absorbing the amino acid.

When you eat, there is a rise in blood glucose

food comas energy

When this happens, your pancreas secretes insulin in order to allow this glucose to enter your cells to be used for energy.

However, after eating large amounts, the insulin released may not be enough to bring your blood glucose levels back to where they were prior to eating.

When this happens, the availability of tryptophan enhances, encouraging drowsiness.

However, it is not just higher blood glucose levels that can cause symptoms of sleepiness, as sometimes the pancreas can actually overshoot the amount of insulin present in the blood, like in circumstances where the insulin sensitivity of cells is reduced.

In this scenario, blood glucose levels can decrease below that of baseline (rebound hypoglycemia), which can also cause feelings of tiredness, as there is less blood glucose available to be used as energy by your cells.  

On the other hand, serotonin can contribute to wakefulness also, depending on the area of the brain it’s secreted.

Further, serotonin contributes partially to making another hormone, melatonin, the main hormone that induces sleep.

Melatonin is primarily produced by the amount of light your body is exposed to.

When it’s dark, your body will make more melatonin, causing you to feel tired, while the light will cause you to feel more awake.

Secondly, food comas may occur due to changes in blood flow, which may lower our energy stores.

This is because when you consume food, more blood flow could be needed by the small intestine in order to be able to sufficiently process the food.

Consequently, this shift of blood flow may result in the brain receiving less oxygen, influencing drowsiness!

However, there is debate surrounding this hypothesis as blood flow in the brain is maintained well in response to various aspects like exercise.

Also, digestion may contribute to food comas because it changes our body from being in a sympathetic state to a parasympathetic state.

And what does this mean?

Well, your sympathetic nervous system is the part of you that deals with stress in everyday life.

You may have heard of it referred to as your fight, flight or freeze mechanism when confronted with difficult situations in life because you only have these three options to choose from in order to deal with that associated stress.

On the other hand, the parasympathetic system is known as the rest and digest state, controlling other functions that we use in the absence of stress, such as digestion, conversing bodily energy by slowing down your heart rate and blood pressure and supporting the processes which cause sleep.  

A third theory that might be contributing to food comas is a cytokine (a small protein with an essential part in the inflammatory process), known as interleukin 1, that is activated following food intake.

Increased levels of this cytokine have actually been found in multiple disorders associated with fatigue, such as obesity, multiple sclerosis, cancer and diabetes.

Although a study by Lehrskov et al. suggests that, most likely, interleukin 1 is not the main driver of feelings of tiredness following large meals but rather a partial contributor. 

Finally, neuroscientists investigating the brain activity of sea slugs have suggested that from an evolutionary perspective, a food coma could in part be a way of promoting long-term memory storage, as sleep is when we process memories from our waking hours.

One reason why this may be is that when we were roaming around the earth tens of thousands of years ago as hunter-gatherers, food comas may have helped us remember places of high food availability.

However, again, this is only speculative.

It’s important to note that food comas may not only be a response to eating large quantities of food at one sitting but could be the consequence in certain incidents from an underlining health condition like diabetes. 

Therefore, if you find their severity or frequency is concerning, please visit your general practitioner regarding this. 

To read our blog about Intermittent Fasting and Health, please follow the link here.

How to avoid the impact of food comas on energy

food comas energy

So what are some of the ways that we may reduce, if not avoid, food comas after eating?  

Well, the first is to obviously reduce the abundance of food you consume at meals where you normally overeat.

By instead having smaller but more frequent meals during the day, we can help avoid food comas altogether.

The second thing we want to do is limit the number of bad carbs (refined carbs) we have at meals while improving the number of good carbs (whole carbs).

Whole, unprocessed carbs are good as they’re full of nutrients and fibre, which help satiety and don’t result in the same level of spikes and dips in the amount of glucose in our blood (which causes cravings) than refined, processed carbs do.

Types of whole carbs are whole grains, vegetables, fruit, legumes, while types of refined carbs are candy, pastries, white bread and white rice.

Next, a good idea is to drink adequate amounts of water prior to meals, as this has been shown to reduce food intake levels.

A good amount to aim for is a glass of water, roughly about half an hour before you eat.

And lastly, ensure you are getting enough sleep as you will be more prone to feeling tired following a meal if you are not getting at least 8 hours of sleep nightly.

Further, ways you can help this is by making sure you have a mattress that is suitable in terms of height, setting a reasonable time to go to bed and staying consistent with it, keeping the room temperature at an appropriate level, turning off the lights, avoiding coffee, cigarettes, alcohol and heavy meals before you sleep and covering all electronic devices in your room that emit light.


To conclude, the reason or reasons why we experience food comas after eating large meals even though they should hypothetically provide us with more energy is currently not known, but several theories surrounding their presence may be due to hormonal responses, deviations in blood flow, pro-inflammatory cytokines, a shift from the sympathetic to the parasympathetic system or even an evolutionary mechanism which could have a partial facilitator in the survival of the human race.

Luckily, there are some daily things we can do to limit foods comas, such as having smaller meals more frequently throughout the day rather than just the three big meals of breakfast, lunch and dinner, including more good carbs at each sitting while reducing bad carbs, drinking more water before each meal, as well as generally increasingly our nightly sleep.

If you are interested in undertaking one of our evidence-based and results-backed Plato Weight Management programs, please make sure to check what program may be suitable for you at this link or contact us here!

You can find out what some of our previous clients had to say about the program on our success stories page!