You know the feeling. What has started as a reasonable day energy-wise quickly unravels an hour or so after lunch when you find yourself feeling so tired that you could literally fall asleep on your desk, in the car or in a meeting.

While a cola, energy drink or cup of coffee may temporarily relieve the fatigue, you find yourself limping to the end most days.

So why is a 3pm slump so common, and most importantly, what are the simple steps you can take to power through the day rather than needing a nap to make it through?

The time of day is relevant

The science behind a 3pm energy slump is surprisingly simple. Human beings are internally programmed according to circadian rhythm or a 24-hour internal body clock that regulates hormone production, carbohydrate and fat metabolism and our sleep/wake cycles.

As part of this cycle, every mid-afternoon there is a natural decline in body temperature and an increase in the production of melatonin, a hormone involved in regulating sleep cycles, which may exacerbate feelings of tiredness and fatigue after lunch.

This effect may also be affected by the nutrient mix and the size of the lunch we eat. It may also be the reason many European countries schedule a rest period immediately after the lunchtime meal to work in with circadian rhythm, and allow the body to recover before powering through the late afternoon and evening.

Why what we eat at lunch is important

Carbohydrate-heavy lunch meals such as noodles, rice, pasta, wraps and large slices of bread result in relatively high amounts of the hormone insulin to be released, which affects blood glucose control.

Large fluctuations in blood glucose levels can affect alertness, energy levels and cravings in the body, leaving you more prone to extreme fatigue an hour or two after eating.

Caffeine intake is also important

Often when we are tired and need an energy hit, we reach for something sweet, a coffee or another source of caffeine to help push through feelings of fatigue.

The issue with relying on caffeine for this hit, is that the hit does not last very long: 40 to 60 minutes at most. This can mean you find yourself feeling even more fatigued an hour or two later, especially if this coincides with the natural lull in energy mid-afternoon.

It can be a sign of hormonal disturbance

While a degree of lethargy an hour or two after lunch is not uncommon, if you have issues with blood glucose control, or have insulin resistance, the effects may be more pronounced.

In this instance, as insulin works overtime to keep blood glucose levels tightly controlled, it can result in discrepancies in blood glucose levels, which is why you may feel constantly tired, craving sugar or so drowsy you may even fall asleep.

For this reason, if you do feel that your energy slumps are especially pronounced, have a waist measurement over 100cm, or have a family history of diabetes, it is time to have your insulin and glucose levels assessed with a medical professional.

It can be managed

The good news is that while fatigue is not uncommon at this time of day, the food choices you make at lunch can go a long way in minimising the effect of a mid-afternoon energy drop.

Protein- and vegetable-rich options such as hearty salads, soup, naked burrito bowls, sashimi and vegetable stir-fries with chicken or lean meat, with less processed carbohydrates such as white bread, rice, wraps and noodles will help manage blood glucose levels and improve energy levels.

The size of the meal too is important. You may find that eating a smaller lunch earlier in the day, such as a light wrap or calorie-controlled meal followed by a vegetable- and protein-rich salad or soup in the early afternoon, will help you avoid eating one large meal, which can also affect digestion and blood flow, again helping to minimise any large fluctuations when a larger meal is consumed.

Most importantly...

While the food we eat can be an important aspect of actively managing your daily experience of energy, one of the most powerful things we can do mid-afternoon to avoid a general lull in energy is to get moving and get outside.

Walking after you eat through the day will immediately improve digestive comfort as well as energy levels, as the blood gets moving to the muscles.

If you can, getting outside in the sun will further aid mood and the production of hormones that remind the body it is not actually time for bed, although there are certainly physiological grounds for a mid-afternoon siesta if you can manage one every now and again.