It’s just gone 3pm, your focus is fading, and the only thing keeping you going is the thought of another cup of coffee or a sugar hit – a sure sign of the afternoon slump, but it may not be for the reason you think.
The conventional wisdom has been the sudden wave of afternoon tiredness relates to our food choices at lunchtime.
In fact, scientists now believe that this energy slump is hard-wired into our biology (although the good news, as you’ll see, is that there are diet tricks to help).
It’s thought to be a hangover from our caveman days, when sleeping during the hottest part of the day made the most sense (and is why many hot countries take a long post-lunch siesta).
As a result, your body’s internal clock, which manages your sleep-wake cycle, dictates that sleepy hormones are released in the mid-afternoon as well as when night approaches.
In fact our body clocks ensure that we tend to feel our most sleepy between 2-7am, conveniently when we are usually asleep, but less conveniently also between 2-5pm in the afternoon.
While you can’t override your body clock, you can work with it, tweaking your diet and daily habits for energy and focus in the afternoon. Here’s how:
Nutritionists believe skipping breakfast means the body works harder to digest lunch, causing a bigger shift in blood flow to the gut
Why breakfast matters
After a daytime meal, we can feel a bit sluggish, but when it comes to breakfast, the opposite might be true – skipping it could actually intensify the post-lunch energy dip. That was the finding of a 2018 study in the journal Clinical Physiology and Functional Imaging.
The researchers used ultrasound imaging to measure blood flow in the brain and found that in those who skipped breakfast, blood flow dropped significantly for about an hour after lunch, while those who ate breakfast didn’t experience this dip.
The reason isn’t fully clear, but one possibility is that skipping breakfast means the body works harder to digest lunch, causing a bigger shift in blood flow to the gut.
This could mean less oxygen and nutrients reaching the brain, which might explain why skipping breakfast leaves you feeling less sharp in the afternoon.
So my advice is to grab something for breakfast, even if it’s only a banana, or get into the habit of making overnight oats in the evening if you find yourself short of time in the morning.
Dr Emily Leeming advises avoiding caffeinated drinks after midday, as caffeine lingers in your system for two to 12 hours and may interrupt your sleep without you realising and make the afternoon slump worse the next day
Take energy boosting sandwiches to work
Making sure you eat breakfast will help you stick to a moderate lunch – and that will also help with post-lunch energy levels.
In a 2012 study published in the journal Physiology and Behavior, researchers tested the driving ability of young male drivers after a light lunch (300 calorie) or heavy lunch (900 calorie).
They found that those who had the bigger lunch felt sleepier overall – confirmed by scans showing their brain activity – and they drifted more across the lanes, with the effects kicking in about 30 minutes into the drive.
The researchers think the bigger meal made drivers sleepier because it was high in fat, which potentially triggered hormones that make you feel drowsy.
Instead of a large, rich lunch, opt for something with plenty of protein and fibre to keep energy steady. A sandwich is fine, but make sure it’s made with wholemeal bread and packed with lean protein (chicken, hummus or cottage cheese) along with plenty of veg. Add fruit or a handful of nuts for longer-lasting energy.
Scientists now believe that the sudden wave of afternoon tiredness we experience is hard-wired into our biology
Set a reminder to get up and move
Being sedentary most of the day doesn’t help with the afternoon slump as it slows blood flow and oxygen to your brain. A quick movement break can wake you up and boost focus.
Researchers found that both a single 30-minute morning walk and six five-minute walks (one per hour) boosted energy. But only the short, frequent walks improved mood, reduced fatigue, and curbed food cravings by the end of the day, according to a 2016 report in the International Journal of Behavioral Nutrition and Physical Activity.
The researchers thought this was likely due to both the short stints of movement helping blood flow and because they provided mental stimulation.
Drink water before getting thirsty
Our brains are 75 per cent water and are particularly sensitive to changes in hydration levels – even a 1-2 per cent drop is enough to affect how we think and feel, leading to sluggishness, trouble concentrating and even small dips in mood.
The tricky part is we don’t usually feel thirsty until we’ve already hit this level – so by the time we reach for a drink, our body is already playing catch-up.
A 2020 study in the International Journal of Environmental Research and Public Health found that after 12 hours without fluids overnight, drinking two glasses of water (500ml) in the morning improved mood, energy, and working memory, while just one glass (200ml) helped with mood and energy.
A half a glass (100ml) wasn’t enough, and skipping water completely left participants tired and grumpy.
So do a fluid check at lunchtime and make a point of drinking two glasses of water with your lunch.
But avoid caffeinated drinks after midday, as caffeine lingers in your system for two to 12 hours and may then interrupt your sleep without you realising and make the afternoon slump worse the next day.
Eat a handful of berries at lunch
Berries might not strike you as a natural afternoon energy booster, but research suggests they can be – even if you have them earlier in the day.
In a 2019 study published in the journal Nutrients, participants were given a 400ml frozen berry smoothie (made with strawberries, blueberries, blackberries, and raspberries) or a placebo drink (matched for carbs and vitamin C) at 9am.
The volunteers were then asked to undertake mental tasks, repeating them every two hours for six hours until 3pm – right when the afternoon slump usually hits.
Berries are packed with flavonoids, plant compounds that can cross into the brain, a feature that sets them apart from many other nutrients
The placebo group experienced a drop in their mental performance as the day wore on; those who drank the berry smoothie stayed sharper, maintaining their accuracy and responding faster.
Berries are packed with flavonoids, plant compounds that can cross into the brain, a feature that sets them apart from many other nutrients. They support learning and memory while also reducing inflammation and oxidative stress (cell damage) – both linked to cognitive decline.
Berries won’t give you a caffeine-like jolt, but they should take effect within two hours, according to the same study. Even a handful of mixed berries after lunch may help, or have for breakfast with yoghurt, porridge or blended into a smoothie.
Step outside for a dose of sunlight
Natural light instantly boosts alertness and focus – in fact a 2025 study in PLOS One found that bright daylight helps us focus and process information more effectively.
People performing tasks in bright daylight did better than those in dim, warm-white light, suggesting even a short burst of daylight sharpens thinking.
Light signals the brain to stay alert, boosting focus and mental clarity. If you’re struggling with the afternoon slump, step outside for a few minutes, sit by a window, or try a daylight lamp if you are indoors all day.
