The Afternoon Slump – Decoding the Biology Behind the Post-Lunch Dip

What Is the Afternoon Slump? — A Natural Occurrence

The afternoon slump, also called -post-lunch dip, refers to a feeling of low energy in the afternoon that many people experience irrespective of their chronotype (larks: peak early or owls: peak later). This sudden decline in energy typically occurs in the early to mid-afternoon between 12 am to 3 pm. It often involves feelings of drowsiness, reduced concentration and focus, and a decline in physical and cognitive performance. [1]

Biologically, this phenomenon is due to your body's 12h harmonic, a part of the circadian rhythm, which regulates your sleep-wake cycle. Additionally, your blood sugar levels change after you have your lunch, and the digestion process can also contribute to the feeling of low energy in the afternoon. Still, even people who did not have lunch or are unaware of the time experience afternoon slumps. [1] [2]

But how exactly does this happen?

Why Do I Get Tired In the Afternoon?

Experiencing a drop in energy and alertness in the afternoon is widespread. You might think that this experience is a matter of habit or your lifestyle, but it is deeply rooted in human biology and underlying processes that occur in your body during the day, especially those of your body’s internal clock. [2]

We will now delve deeper into the biological factors that cause or contribute to the afternoon slump. These include your circadian rhythm, hormonal fluctuations, dietary impacts, and brain chemistry changes during the day.

1. Your Body’s Internal Clock – The Circadian Rhythm

The circadian rhythm is your internal biological clock, significantly influenced by external cues, particularly the cycle of light and darkness, which aligns bodily functions with the day-night cycle. This internal clock orchestrates a wide range of your bodily functions, including your sleep-wake cycle, hormone release, and body temperature, in a roughly 24-hour cycle to match the Earth's day-night pattern. The 12-hour harmonic of the circadian rhythm is one of the reasons why you experience the post-lunch dip/afternoon slump, a natural decrease in energy in the afternoon. [3]

But what is the 12-hour harmonic?

Harmonic, in this context, refers to smaller cycles or fluctuations within your primary 24-hour circadian rhythm. The 12-hour oscillation is a significant harmonic, a shorter cycle within your circadian rhythm that creates periods of increased and decreased alertness within your day. Interestingly, this is an evolutionarily conserved remnant, meaning it's a trait that has been preserved throughout evolution due to its adaptive advantages for humankind to survive. [3]

During midday and afternoon, typically between 12 AM and 3 PM, the release or inhibition of different hormones leads to increased feelings of sleepiness. This dip is a biological signal for a brief period of rest, a remnant from our ancestors' sleep patterns. This harmonic essentially reinforces the body's natural inclination to feel sleepy after the peak alertness period in the morning. As a result, this secondary oscillation works in tandem with other factors like digestion and blood sugar changes post-lunch, intensifying the feeling of tiredness in the afternoon. [3]

While the circadian rhythm is the root of your post-lunch dip, the mentioned hormones and changes in brain chemistry are the explicit causes of why you feel sleepy and tired.

Brain Chemistry & Hormonal Changes

Your circadian rhythm regulates several hormones like melatonin, cortisol, and insulin – all playing a role in the afternoon slump. [4]

Melatonin, known for inducing sleep, gradually increases as evening approaches, while cortisol, which boosts alertness and energy, typically declines in the afternoon, further intensifying feelings of tiredness. Serotonin, a neurotransmitter that contributes to feelings of well-being and happiness, is increased after eating, especially by foods rich in carbohydrates. This increase in serotonin can enhance feelings of relaxation and drowsiness. [4] [5] [6]

As you can see, your internal clock and the associated brain chemistry are the primary aspects that affect how you feel during the day or the next day. Your sleep quality and potential sleep disorders like sleep apnea or even just sleep deprivation can furthermore increase your experience of an afternoon slump. [5]

Another brain chemical that can majorly contribute to the afternoon slump is adenosine which stands in close connection to your consumption of caffeine.

2. Dietary Impacts – Caffeine, the Fuel of the Afternoon Slump

What you eat for lunch and when you drink caffeine can significantly impact your afternoon energy levels. By habit, many of us drink coffee in the morning and before or during the afternoon. This is a huge contributor to the afternoon slump. But why?

As soon as you wake up, a brain chemical known as adenosine begins accumulating in your brain, contributing to the increasing need for rest, called sleep pressure. Caffeine counters this by binding to the brain's adenosine receptors, misleading you into feeling more awake even when sleep pressure is high. However, even as caffeine occupies the adenosine receptors, your adenosine levels continue to rise. [7]

When your body eventually breaks down the caffeine, you experience a sudden increase in sleepiness and sleep pressure due to the rapid release of the accumulated adenosine that has been “waiting impatiently” to attach to its adenosine receptors. This typically leads to an energy crash, frequently occurring in the afternoon.

Another aspect influencing the afternoon crash is your diet. Meals high in carbohydrates can cause a spike in blood sugar levels, followed by a rapid drop, leading to fatigue. This is because high blood sugar levels trigger the release of insulin, which helps glucose enter your cells for energy. Once the glucose is metabolized, the sudden drop in blood sugar can leave you tired and lethargic. For many people, this happens after lunch or in the afternoon, affecting their workday. [2]

Furthermore, the process of digestion diverts blood flow to your stomach and intestines, which can also contribute to a decrease in energy levels as your body focuses on the digestion process.

5 Ways to Overcome the Afternoon Slump

If you wish to soften or trick your midday slump, there are specific methods to keep the tiredness at bay. Energizing your body during the afternoon slump is a clever way to regain some vigor to keep going for the rest of the day.

CARE has curated five scientifically proven ways to energize your body and support your circadian rhythm:

No.1: Avoid Caffeine in the Afternoon

As you have already learned, your daily cup of coffee in the afternoon, or an energy drink containing high amounts of caffeine, is not the best pick-me-up to avoid the afternoon crash – quite the opposite. We are not saying you should not drink coffee at all, but you should time your coffee breaks.

Pro Tip: To avoid the afternoon slump, it is advisable to refrain from consuming caffeine during the first 60–90 minutes after you wake up. After you wake up, your cortisol levels are naturally high. You should only take to your first cup of coffee as soon as your natural cortisol levels drop– 60–90 minutes after waking up. When drinking coffee in the afternoon, you should wait until the afternoon slump has passed before you drink your next cup of coffee. [7] [8] Between your coffee breaks, make sure to drink enough water to stay hydrated and avoid drinking coffee in the evening altogether.

These strategies can help you keep your natural cortisol and adenosine levels in balance despite the consumption of coffee.

No. 2: Cherish Your Internal Clock

Getting enough sleep and maintaining a consistent and stable sleep schedule is critical to avoiding the mid-afternoon slump. [4]

To achieve this, set yourself a goal of getting 7–9 hours of sleep and go to bed on time.

If you have an inconsistent sleep schedule, do not sleep enough, or disrupt your circadian rhythm by drinking coffee at the wrong times, your internal clock gets out of balance. This can lead to extreme afternoon slumps or leave you already waking up tired. [4]

No. 3: Food for Energy

To combat the energy dip you experience during the afternoon slump, carefully selecting your foods, specifically your breakfast and lunch, and a healthy snack can be key.

Avoid foods high in simple carbohydrates, such as sugary snacks, white bread, and processed foods, as these can cause rapid spikes in blood sugar followed by fatigue as your blood sugar levels drop.

Choose foods and snacks rich in complex carbohydrates, like whole grains and veggies, to provide a sustained energy boost without the rapid blood sugar spikes associated with simple carbs. Keep this in mind for your breakfast and lunch. [9]

Furthermore, incorporating healthy fats, such as those found in peanut butter and avocado, can also help maintain energy levels, as they are metabolized slower than carbs. Choosing the right food can provide you with both immediate and lasting energy to mitigate afternoon fatigue. [9]

No. 4: Take a Power Nap

Research shows that a quick nap before your afternoon slump can effectively combat the natural dip in energy.

Power naps, typically lasting between 10 and 20 minutes, have been found to significantly improve alertness and cognitive performance, offering a valuable remedy for afternoon fatigue. [1]

A study from 2010 has found that short naps not only alleviate sleepiness but also enhance alertness, making them an ideal response to the natural decline in energy many experience in the afternoon. This research underscores the benefits of integrating a brief rest into your daily routine to rejuvenate your mind and body during the day. [10]

No. 5: Spend Time in the Sun & Move

Scientific research has consistently highlighted the role of physical activity in enhancing overall health and sleep quality. Engaging in even a short period of exercise increases the blood flow and oxygen supply to your brain, thereby boosting energy levels and cognitive function. Incorporating light physical activities into your workday can improve your mental health and reduce feelings of fatigue. [11]

Additionally, exercising outdoors in nature, especially in sunlight, increases your vitamin D intake and inhibits melatonin production, contributing to improved energy levels, making it a powerful tool to counteract your afternoon lethargy and energy slump. [11]