At its worst jet lag can make you feel like you've got a massive hang-over - but without the memories of a good party the night before. It can cause headaches, memory loss and make it difficult to sleep. There are even accounts of jetlagged business executives failing to remember anything about an important deal they've negotiated.

Jet lag is caused by flying across time zones faster than your body can adjust to the change. Most travellers agree that it's less disruptive to fly west because the body's natural rhythm is a 25-hour day and it can deal with a longer day more easily. Very roughly, you can expect to take one day to adjust to each hour of time difference.

There are several ways of tricking your body in to adjusting faster to a new time zone. Book overnight flights when heading east so you can sleep on the plane, or flights that arrive at night, so that you can sleep when you arrive. If you're on a night flight aim to take off after 10pm so that your body clock will allow you to go to sleep and you can have a proper meal before you board. Plan meetings when you're at your most alert - for most people this is 8-10am or late afternoon.

Gear up for a long-haul flight by getting plenty of sleep and exercise in the days before hand. Gradually adjust your bed and meal times so that they are closer to the time zone you will be flying to. If you're heading to New York, for example, stay up a little later. Start going to bed slightly earlier in the days before you're due to return.

Resetting your body clock

Sunlight tells your body that it's daytime so exposing yourself to rays - or avoiding them at certain times - will help your body to adjust faster. Food is another important trigger so try to move your mealtimes so that they are closer to the corresponding times in the country you're flying to.

As soon as you get on the plane change your watch to show the time of where you're going. Sleep on the plane if it is bedtime in your destination. Wear eyeshades and tell the flight attendants not to wake you up until the very last minute. If it's daytime at your destination try to stay awake.

Wearing light visors (such as those supplied by lumie.com) can help you to stick to a light/dark routine without being tied to a lightbox. The visors, which are also used for Seasonal Affective Disorder (SAD), shine bright lights onto the eye which helps to reset your bodyclock and also helps you to stay awake.

Diet and exercise