After a large meal, blood is diverted to the intestines to digest food, which means less oxygen and nourishment is reaching the brain.

You can blame it partly on your biological clock. In the 24-hour cycle of the body, or its circadian rhythm, our bodies are biologically programmed to “shut down” for sleep twice during each 24-hour period. We feel naturally tired at night, which is when we go to bed, and unfortunately, the other time is around 2pm, which is after lunch!

It’s not likely that you can sleep it off at work, but there are some things you can do to stay awake after lunch.

Take a short walk

This is the easiest way to recharge. Don’t go back straight to your desk after lunch, but walk around the office, even if it’s just a five-minute stroll around the building. If you’re working in a high-rise building, take the stairs instead of the lift.

Exercise during lunchtime

It’s even better if you can fit in a workout during lunchtime. Exercise increases blood and oxygen flow, releases tension and produces endorphins, which can help you feel more energised.

Eat a light lunch

Since heavy meals are partly the culprit, one way round this problem is to avoid eating so much during lunchtime, but to eat five to six smaller meals throughout the day. Start the day with a nutritious breakfast and have small mid-morning and afternoon snacks.

This helps keep blood sugar and insulin levels steady, which prevents fluctuations in serotonin levels in the brain. Serotonin is a neurotransmitter associated with sleep.

Eat the right foods

Refined carbohydrates such as potatoes, white rice and white bread, and sugary foods raise insulin levels rapidly. Switch to complex carbohydrates and food that’s high in protein and fibre instead. Wholegrain breads and cereals, beans, lentils, vegetables, fruits, lean meat, fish and tofu take longer for the body to digest, which means your insulin levels rise far more slowly.

Drink coffee

Most people reach out for a cuppa to keep them going. But responses to caffeine vary, and for some people it can disrupt night-time sleep. Try green tea instead. It’s lower in caffeine and is less likely to lead to a caffeine addiction; yet it’ll still keep you alert.

Sleep well at night

One cause of daytime drowsiness is not having a good night’s rest. If you find you're having trouble sleeping, limit your intake of caffeine after lunchtime and develop good sleeping habits. A vicious circle can occur when you don’t sleep well at night, making you consume more caffeine to get through the next day, making it difficult to fall asleep the following night.