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May 11, 2017

How the food you eat affects workplace productivity

prawn salad in a bowl

Your choice for lunch will affect energy levels throughout the day

The “post lunch lull”

It’s something we’ve all been affected by after a particularly heavy midday meal, trudging back to the office to find all those afternoon tasks we’d had lined up simply seemed much more difficult than we’d envisaged.

But why?

Well, what you eat (and when) affects how you work.

It might sound sensationalist, but the choice of where you and your team decide to take lunch can have a huge effect on their productivity and concentration levels.

A quick biology lesson

The brain needs energy to function properly.

The fuel that it works off is glucose (i.e. sugar) which comes from breaking down the food that you eat.

After eating, this converted energy gets sent from your stomach up to the brain so that it can do something useful.

As with most machines, your brain runs best when there is a smooth and constant supply of energy, and begins to falter (i.e. become less productive) if it’s succumbed to big spikes and troughs of its energy source.

A sudden drop in energy makes it more likely for your brain to begin to switch off, seek distraction and generally result in a feeling of apathy towards that important thing that lies in front of you.

Maintaining a steady level of energy means you are much more likely to remain focused and productive on the task at hand.

How food becomes fuel

Now, from a brain performance perspective, not all food is created equal.

The important connection to make is the link between the food that you eat and the length of time that it can provide energy to your brain.

This concept was formalised into what scientists refer to as the Glycemic Index (GI).

It’s a measure of the rate at which a type of food is converted into glucose, and consequently its effectiveness at keeping the brain productive.

A high number suggests energy levels will shoot up and drop sharply after eating, and a low number indicates that it will send up a smooth and steady supply of brain fuel to help keep you on task.

A picture might make this clearer:

glycemic index chart

Energy levels after eating different GI foods

 The ideal scenario is for there to be as little fluctuation in the energy levels as possible throughout the period when you want your brain to be useful.

Slowly slowly wins the race

Viewed this way, the question then becomes: how to keep glucose levels as stable as possible throughout the day?

There are various approaches, all of which will contribute to maintaining a focused mind and a productive output.

Go for low GI foods

When it comes the food choices you make you typically have the control to decide what types of food to eat.

In general, avoid anything starchy, sugary and processed which causes spikes in your energy levels. For example:

  • Potatoes
  • Rice
  • Doughnuts

Conversely, choosing food which is whole grain, unprocessed and generally low in sugar will mean that your brain will reap the benefits for hours to come.

Things like:

  • Oats
  • Green vegetables
  • Brown bread

Avoid big meals

Whenever you take on a plateful at the lunchtime buffet your brain is soon in for an overload of glucose.

Of course, you need to eat, but concentrating this all into one big midday meal creates one big midday spike in your energy levels.

Reducing the impact of the lunchtime meal will do wonders for your productivity.


The obvious riposte to reducing the size of lunch though is: but I’ll get hungry!

Well, the primary way to counter this is by grazing on snacks throughout the day. The small boosts to your glucose levels will reduce cravings for quick (often unhealthy) bursts of energy in the form of sugary snacks, and mean your brain will be running on a steady supply of energy.

As before, not all snacks are made equal.

The short answer is: have a bowl of nuts by your desk.

But here is also a list comparing high GI snacks and alternatives


With all this talk of food, it’s important to not forget the related aspect: what you drink.

By now it should be predictable to learn that sugary soda drinks will contribute to your glucose levels shooting up and down, and so to be weary of when you have them, and why you might be.

Beyond the notion of glucose levels though, there is the additional consideration of how hydration affects how your brain functions. It’s not just energy that it requires to be productive, but also for you to be hydrated.

The idea of “drinking water is good for you” is quite commonplace nowadays, and for the purposes of this post, I’ll merely point you in the direction of the following studies that link how dehydration causes a reduction in the ability to complete executive functions, and even a link to an increase in industrial accidents.

What’s more interesting is finding a way to make drinking water more of a habit: despite knowing that it is a good idea to drink more, a lot of us rarely do.

A simple resolution to this is; put a jug of water on your desk.

You’ll likely spend a similar number of trips to the tap or water cooler than if it was a small glass, and doing so will compel you to stay hydrated throughout the day.

Eating at the desk

The closing point to make is the impact of where you eat your lunch, and who with.

In the fray of a busy day, it often feels that cramming down a sandwich whilst catching up with emails is the only way to stay on top of things.

Whilst it’s impossible to make a universal comment on everyone’s work schedule, there have been several studies showing how the act of getting up and walking around throughout the day has not only health benefits, but also keeps your brain stimulated.

From a company culture perspective, instilling an environment where colleagues socialise increases overall outputs. Lunch time is prime time.

Practical points

Based on all of this, it’s helpful to distil the key habits that you and your team can take on to improve productivity throughout the work day (or indeed beyond).


  • Snack on nuts and other low GI foods throughout the day
  • Have a jug of water at your desk so you drink more
  • Avoid big, starchy midday time meals
  • Go for a walk around the block at lunchtime, preferably with colleagues


We hope that you found this post informative and thought-provoking. If you’d like to be notified of the next post, or learn more about how Inspira UK can help your business grow, then you can sign up to the newsletter and contact us here.

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