How does jet lag affect the body?

Updated February 21, 2017

Jet lag is the blanket term for the physiological and psychological changes that occur when your body is adjusting to a different time zone. The associated disruption to your circadian rhythm, the scientific name for your internal body clock, causes jet lag. Symptoms are more severe if you travel across two or more time zones but you can alleviate the effects of jet lag and recover more quickly by resisting the urge to nap when you reach your destination and establishing eating and sleeping routines that conform to your new time zone.

Understanding the circadian rhythm

Your circadian rhythm is governed by a group of light-sensitive brain cells that responds to signals from your retina -- meaning that you’ll feel alert during the daytime and start to wind down at night These brain cells, known at the suprachiasmatic nucleus, help to regulate your body temperature, appetite and some hormonal activity, as well as your sleep and waking cycles.

Disrupted sleep cycles

Travelling across time zones disrupts your circadian rhythm, or internal body clock. For example, if you visit New York, which is 5 hours behind the UK, your internal clock will still be set on London time. Therefore, going to bed at midnight in the Big Apple and getting up at 8pm, is your circadian rhythm’s equivalent of turning in at 5am and rising at 1pm. Jet lag’s most immediate effect is that you’ll feel sleepy during daylight hours and wide awake at night.

Physical effects

Fatigue, loss of appetite, light-headedness, muscle soreness, nausea, indigestion, gastro-intestinal upsets and headaches are common symptoms of jet lag. Although some symptoms arise from the insomnia that typically comes with jet leg, some can also result from the associated hormonal changes that affect your body temperature and appetite.

Psychological effects

The physical effects of jet lag can also affect your mental well-being. You may feel mildly depressed, irritable, confused and have difficulty concentrating. Cut down on caffeine while you are adjusting to the new time zone, because too much coffee and fizzy drinks can exacerbate these symptoms. Getting a good night’s sleep before you travel also helps you to cope with the psychological and physical effects of jet lag.

The flight factor

The decreased air pressure in plane cabins equals reduced oxygen, which can cause dehydration and make you feel lethargic and out of sorts. Symptoms can be more severe if you suffer from a medical condition, such as heart disease, anaemia or lung disease, that affects your oxygen levels. Drinking plenty of water before and during the flight and abstaining from alcohol helps to counteract these effects.

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About the Author

Based in Belfast, Northern Ireland, Elizabeth Burns began writing professionally in 1988. She has worked as a feature writer for various Irish newspapers, including the "Irish News," "Belfast News Letter" and "Sunday Life." Burns has a Bachelor of Arts in English literature from the University of Ulster as well as a Master of Research in arts.