Jet lag is the upsetting of the circadian rhythm, resulting in the alteration of bodily functions. The circadian rhythm of bodily functions is linked to sunlight. Research shows that a hormone called melatonin may help eliminate jet lag by halting and restarting the body's circadian rhythm. However, work on the subject is still at the research stage.

While there is not one clear medical denifation what causes jet lag, it is my experience that the condition results from a combination of the following factors:

• Time. Gaining or losing time as you travel results in your body clock being confused about its routine.
  
• Impact of pressurization on the body. The atmosphere is thin at great heights. Despite the fact that cabin pressure is adjusted accordingly, but pressure is greater than its surroundings, and there is a consequent bloating of the body to compensate for this.
  
• Low moisture content of the atmosphere. A loss of fluids leaves the body with a feeling of being drained.

• High speed. You are traveling at great speed on flights, at 800 to 1,000 km an hour. Although this is not felt as in the case of, say, travel on the road, the high-speed motion does affect your biorhythm and metabolism.
  
• Change in cycles. The eating, drinking and sleeping cycles that your body is used to has been turned into complete disarray, adding to the confusion caused to your metabolism.

The results of jet lag cover a range of conditions such as fatigue, confusion, loss of appetite, upset bowels, excessive sensation of heat or cold, inability to sleep when you are supposed to, and waking up when you are not supposed to.

Here are some ways in which to manage jet lag:

• Try to adjust to the time cycle of your destination even before departure. If you are to be served breakfast on a flight soon after you have dined on ground, skip or make a light meal of dinner rather than breakfast. Then, if it is lunch time when you arrive, you are ready to eat.
  
• On the flight, set your watch by the time at your destination; eat and sleep according to this timing.
  
• If you are gaining time traveling from east to west, try and sleep a little earlier so as not be tired during the extra time you have to stay awake at your destination. Do the opposite when traveling in the other direction.
  
• On arrival, slip immediately into meal and sleep cycles generally followed at your destination. Try to sleep the same time every night and take meals at the same time every day.
  
• East foods that are high in fibre, such as fruits, vegetables and carbohydrates (bread, pasta and rice). These are easier to digest.
  
• Avoid alcohol and coffee the day before departure and while you are in the air, as these are diuretic.
  
• Rest before traveling to feel fresh.
  
• Use moisturizers to combat dryness. Avoid contact lenses as these have a drying effect on the eyes.
  
• Pep up circulation on arrival by going for a walk or swim. Warm baths and light exercises can be helpful. Avoid excessive exercise.
  
• To prevent getting swollen feet, the result of sitting in the same position for too long and of a change presurrisation, it is essential to wear loose, spacious shoes that can be removed once you are seated. You can increase blood circulation to the feet by rotating your ankles and walking around the cabin whenever possible.
  
• Get sunlight, it revitalizes you.

For very short trips or transit stops, it may be best to keep to the time of your final destination. Sleep experts in the United States suggest that hotels create East Coast and West Coast rooms with controlled lighting to make travellers feel as though they were in their normal time zone.

Nowadays, a quick-acting mile sedative, if you tend to be the hypertensive type, is recommended, especially on long flights. Sleep experts also say that exposure to sunlight in the daytime may be a good way to minimize the fatigue that comes with jet lag because sunlight helps regulate late the body's biorhythms. If daylight is not available, then exposure to three 150-watt light bulbs will have the same effect on the body's circadian rhythm. Tokyo's Hotel Okura offers its clients the benefits of such light exposure. Professionals advise travellers to consume high-protein foods in the morning for energy and carbohydrates in the evening to induce sleepiness.

Jet lag is a serious matter. In the past, certain firms, particularly Japanese ones, actually worked this factor into guidelines for traveling executives. If the total travel time exceeded eight hours - starting from departure from home or hotel to arrival at the next hotel - no business meetings were permitted for a period of 24 hours. The aim was to allow the body to adjust itself, thus avoiding the possibility of jet lag impairing business judgement and decisions.

My ultimate experience of jet lag took place in my younger days. After full day of work in West Africa, I set off on a flight to New York. This entailed 12 hours of flying time with one stopover. I then had an onward connection from New York to Tokyo which involved a flight that was, at the time, the longest nonstop flight in the world on 747 special: 13 hours and 45 minutes!

The flight to New York was delayed by about four and a half hours so after more than 16 hours in the air and in transit, I had to travel for another 14 hours, arriving at Tokyo rather late at night. My meeting the next day had been scheduled for the late morning with the intention of giving me time to recover from the journey.

While I did manage to sleep that night, the morning meeting found me a complete zombie. I was not merely tongue-tied, but literally speechless. I cut a sorry figure when I had to explain to a Japanese colleague that I had foolishly overstepped the limits of my biological capacities, and hence was ill-equipped for the meeting.