You've just enjoyed a tasty burger for lunch and are back at your desk slugging away. Five minutes in and you're overwhelmed with sleepiness, so much so that the space under your desk is looking pretty damn comfy right about now.
But why do we get sleepy after lunch? Is it just because we're full, or is it a sign we're not doing lunch right?
"Feeling a little tired after eating a meal is perfectly normal," Robbie Clark, dietitian and sports nutritionist, told The Huffington Post Australia. "There are a few reasons why we experience the post-lunch slump, but the main reason is due to the digestive process."
Although it might not feel like it, the body uses a fair amount of energy to digest the pasta you've just eaten.
"Our body requires energy to function and survive. We get this energy from our food, which is broken down through the digestive process and converted into fuel, or glucose, and then macronutrients provide calories (or energy) to our bodies. Our digestive system triggers all kinds of responses within our body," Clark explained.
Another reason we may feel sleepy after lunch, or after eating in general, is due to the amount of insulin produced after certain meals, which can trigger our 'happy' and 'sleep' hormones.
"After eating -- particularly sugary foods -- insulin is produced by the pancreas which then converts these sugars (glucose), circulating in the bloodstream into glycogen within our cells," Clark said.
"Excessive secretion of insulin causes the essential amino acid tryptophan to move into the brain. Once in the brain, it leads to increased production of serotonin and melatonin, which are two neurotransmitters that have a calming effect and help regulate sleep. Interestingly, around 90 percent of the body's serotonin is found in the gut, where it regulates intestinal movements."
Accredited practising dietitian Jemma O'Hanlon agrees, saying the amount of carbohydrates we eat at lunch can affect how sleepy we feel afterward.
"Carbohydrate containing foods such as bread, pasta, rice and potatoes boost the production of a neurotransmitter known as serotonin, which can boost our mood but also make us feel content and possibly sleepy," O'Hanlon told HuffPost Australia.
"It's often when we've eaten quite a large meal that we may feel uncomfortable and sluggish, as well, so it's always good to listen to our hunger signals and stop when we feel comfortably satisfied."
Another factor that may contribute to drowsiness after a meal is if you suffer from a food allergy or intolerance.
"Food allergies and intolerances are usually associated with digestive problems such as bloating, gas, reflux, indigestion, constipation or diarrhoea, as well as lethargy," Clark said.
"Finally, general overeating, large portions and the consumption of particularly fatty meals can leave you feeling sleepy because the body has to work overtime and utilise more energy to break down the quantity of food."
On top of these physiological reasons as to why we may feel sleepy after lunch, there are also a few other key foods which can contribute.
"Though all foods are digested in much the same way, not all foods affect your body in the same way," Clark explained.
"For example, you've probably heard or experienced that turkey can make you sleepier than other foods. Turkey and other high protein foods such as spinach, soy, eggs, cheese, tofu and fish contain higher levels of tryptophan. Studies have shown that cherries (particularly sour cherry) affects melatonin levels, which is the hormone responsible for inducing sleep."
Another sleepiness inducing food is white bread, particularly when compared to whole grain, wholemeal or multigrain bread.
"When you consume white bread your body quickly absorbs the fibre-less starches and refined sugars rapidly, which causes a spike your blood glucose levels. This spike is short lived and results in plummeting blood glucose levels, which can lead to feelings of tiredness and sleepiness," Clark said.
To avoid after lunch sleepiness, Clark and O'Hanlon recommend the following.
1. Don't skip breakfast
We've all been told how important breakfast is for both our bodies and mind. According to Clark, eating breakfast can also help reduce tiredness later in the day.
"If you skip breakfast, it sets the energy standard for the rest of the day," Clark said. "Plus, come lunch time you will be extremely hungry and are more likely to make poorer food choices or have a larger portion."
2. Eat smaller meals throughout the day
"A large meal requires more energy to digest. Instead of eating large lunches, you may want to try eating smaller meals throughout the day," Clark said.
"For example, balance a small lunch with mid-morning and mid-afternoon snacks so that you meet your recommended dietary intake of calories throughout the day."
"Eating smaller, more frequent meals across the day can help keep our blood sugar levels steady and give us those regular top ups of energy," O'Hanlon added.
"It's never good to overdo it at any meal, and getting the balance of carbohydrates, proteins and good fats can help fuel us for longer."
3. Opt for macro-nutrient balanced meals
"Instead of choosing processed foods and starchy sides, make sure that your lunch is balanced and healthy by opting to have a lunch that features colourful vegetables as the main attraction, and a serving of whole grains and lean protein," Clark said.
"Other food tips to avoid slumped energy levels include drinking plenty of water to stay hydrated, avoiding too much sugar and refined carbohydrates, and eating smaller, more frequent meals.
"Also, to help balance blood sugar and insulin levels, choose natural foods that are high in fibre and protein such as whole grains, legumes and nuts."
To know how to choose (or make) macro-nutrient balanced meals, O'Hanlon recommends focusing on the healthy plate model.
"Aim for half your plate to be non-starchy veggies, one quarter to be lean meat or alternatives, and one quarter to be whole grains," she said.
"Often we tend to skimp on the vegetable or salad component, but it's important to get a few serves of our 'five a day' at lunch time and this will help balance the rest of our plate."
4. Go outside or get moving
Instead of spending your lunch time inside, enjoy your meal outside and, if you can, schedule in a walk.
"Exercise can keep you alert during the day by optimising oxygen and blood circulation around the body and to the brain, minimising the risk of your post-meal slump," Clark said.
"Getting outdoors is also going to help increase oxygenation to the brain."
5. Check in with the doctor
If you're constantly feeling tired and it's affecting your day-to-day life, O'Hanlon recommends checking in with a health professional.
"If you're feeling tired it could be also due to a vitamin or mineral deficiency. For example, iron deficiency, which is very common in young females, particular those not eating meat," O'Hanlon said.
"If you're feeling tired regularly, I'd recommend visiting your local GP and having a general check-up."