Out to lunch, not out for the count
Itís well known that peopleís productivity falls after lunch - one recent survey suggests that what it calls "Afternoon Apathy Syndrome" is having serious financial repercussions for UK industry. It also says that what you eat may stave off afternoon lethargy.
The research, commissioned by the makers of Ryvita crispbread, also reveals that many workers - women in particular - are damaging their health by eating at their desks or skipping lunch altogether.
The nutritionist behind the survey, Fiona Hunter, summed up: "Rather than using their lunch hours to recharge and re-energise, most Brits are eating stodgy meals leaving them lethargic in the afternoon."
So, what are we doing wrong and what should we be eating to keep on top of our form throughout the day?
Know your stuff
First of all, we need to know how the body deals with different types of food. The survey argues that as a rule we consume too many carbohydrates during lunch and this makes us lethargic. Bread, pasta and potatoes, provide the body with much of its energy but do take a relatively long time to break down.
Because blood is directed to the gut after eating, less oxygen reaches the brain, reducing its efficiency. The more food there is; the more blood is diverted - which is why granddad falls asleep after Christmas lunch.
Fat is another source of energy but takes even longer to break down and therefore has a further slowing effect on the mind. So large greasy lunches, while often good for hangovers, do nothing for concentration.
Dr Wendy Doyle of The British Dietetic Association suggests avoiding foods high in sugar such as chocolate or cakes because of their knock-on effect of producing insulin and causing a dip in blood sugar a short while later, again reducing the brain's efficiency.
But, while eating too much can have a negative effect, so can not eating enough. "Having too little or even nothing at all can also cause a lack in concentration as your blood sugar level goes down," says Dr Doyle.
A change of scenery
Nutrition scientist Colette Kelly, from the British Nutrition Foundation, argues that food is only one aspect of a post-lunch lapse. "In theory, if you eat a lot of carbohydrates it can influence your mood but in most cases people don't eat enough for that to happen," she says. "The main problem is people not getting up from their desks. A quick walk, a change of environment, it all wakes you up."
Dr Doyle agrees. "Many people have eaten their lunch before they know they've had it. Take a 10-minute break. The mental benefit of going for a walk will do you some good."
Theory into practice
This is all very well in theory, but do our busy lives make it practical? Lucy Sherriff, 26, is a media executive in central London. She remembers the post-lunch slump from her university days, when she was often half asleep during the first afternoon lecture.
In order to keep sharp, Lucy usually eats soup or a sandwich for lunch - something that nutritionists would approve of. But she says she doesn't always manage to do so well.
"I tend to have a big greasy pub lunch when I'm hung-over, which does make me feel a bit sleepy, although much better," she says. "And then, if I'm hungry, I eat a larger amount of food - big pastas usually."
She admits to feeling a little bit tired afterwards but says, "I have a cup of coffee back at work and then I feel fine."
The amount you eat should depend on one factor: how hungry you are. Don't eat so much you feel bloated and don't under-eat to reach some arbitrary target you have come up with. Dr Doyle and Colette Kelly both reiterate commonsense rules: follow a balanced diet and take some form of exercise.
However, many people make the mistake of forgetting fluids. A glass of water or fruit juice will cut down post-lunch dehydration and reduce lethargy.
So what is the ideal lunch for the busy office worker?
Colette says: "Ideally, perhaps a sandwich, wholemeal bread, a lean cut of white meat like chicken. Not too much mayonnaise. A salad or low-fat spread. Perhaps a tuna or egg filling in a baked potato. Some fruit and veg afterwards and drink some water."
There is a way to avoid that afternoon slump. The downside is that if you follow the nutritional advice, you'll have to find another excuse for being late with those afternoon reports.
The British Dietetic Association
British Nutrition Foundation