Why do we sometimes feel sleepy after lunch?

Feeling a little tired after eating a meal is perfectly normal. There are a few reasons why we experience the post-lunch slump, but the main reason is due to the digestive process.

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.

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. 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 per cent of the body’s serotonin is found in the abdomen, where it regulates intestinal movements.

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 affect brain function including lethargy.

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.

Do certain foods or the amount of food matter?

Though all foods are digested in much the same way, not all foods affect your body in the same way. 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 example is white bread versus 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.

Also, the consumption of large meals take time to digest, meaning blood may be diverted away from other body areas, including the brain to help with this process. Furthermore, if you are dehydrated during or after eating, this may exacerbate your levels of sleepiness.

Is there anything we can do to pick ourselves back up after lunch?

There are foods that can have the opposite effect of making you feel drowsy. For instance, a balanced diet that includes vegetables, whole grains, and healthy fats promotes sustained energy. 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 wholegrains, legumes and nuts.

How can we avoid this “after-lunch slump” in the first place? 

  • Don’t skip breakfast– if you skip breakfast, it sets the energy standard for the rest of the day. Plus, come lunch time you will be extremely hungry and are more likely to make poorer food choices or have a larger portion.
  • Avoid processed sugars and flours– Steer clear of croissants, muffins, banana bread, cakes, biscuits and white breads. The higher sugar content will cause a higher spike in your blood glucose levels and bring on the slump more quickly. Instead, opt for wholegrain and unprocessed foods.
  • Eat a complex-carbohydrate, high-protein lunch – 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.
  • Eat less– A large meals requires more energy to digest. Instead of eating large lunches, you may want to try eating smaller meals throughout the day. 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.

When it comes to avoiding the post-lunch slump, there are other things apart from diet and food choices that you can do as well. These include:

  • Get a good night’s sleep– Not getting enough quality sleep can certainly affect how you feel after a meal. If you’re relaxed and full, your body is likely to feel more like resting, especially if you didn’t get enough or had poor sleep the night before.
  • Exercise more– 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. Getting outdoors is also going to help increase oxygenation to the brain.