Jet Lag: Why It Causes Fatigue and How to Recover Faster
Jet lag is a temporary circadian rhythm disorder caused by rapid travel across time zones. Its effects — fatigue, cognitive impairment, sleep disruption, and GI disturbance — are proportional to the number of time zones crossed and the direction of travel.
Why eastward travel is harder than westward
The human circadian clock runs slightly longer than 24 hours (~24.2 hours), making it naturally easier to extend the day (westward travel) than to shorten it (eastward). Eastward travel requires advancing the body clock — falling asleep earlier than it wants to — which is harder than delaying it for westward travel.
The recovery rule of thumb: one day of adjustment per time zone crossed, with eastward travel taking 30–50% longer to recover from than the equivalent westward crossing.
Minimising jet lag before and during travel
Pre-travel: gradually shifting your sleep schedule 1–2 days before departure (earlier for eastward travel, later for westward) reduces the abruptness of the transition. During travel: set your watch to destination time immediately and eat and sleep on destination time, not departure time.
Strategic light exposure is the most powerful jet lag tool. For eastward travel, seek morning light and avoid evening light at your destination. For westward, seek evening light and avoid early morning light.
Recovery at the destination
Melatonin taken at the destination's bedtime (0.5–3mg) helps advance or delay the circadian phase and is well-evidenced for jet lag specifically. Staying outdoors during the day provides the light cues the circadian system needs to resynchronise to local time.
Avoiding long naps during daytime at the destination — keeping them under 20 minutes if necessary — prevents further sleep pressure from dissipating at the wrong time of day and accelerates resynchronisation.
Our assessment can help you understand your baseline fatigue factors before travel to separate jet lag from pre-existing tiredness.
Frequently Asked Questions
Why do I feel more tired after traveling east compared to traveling west?
Eastward travel is harder because it requires advancing your body clock, which is more challenging than delaying it for westward travel. This is due to the natural circadian rhythm running slightly longer than 24 hours.
How can I reduce jet lag before my flight?
To minimize jet lag, gradually shift your sleep schedule 1-2 days before departure, going to bed earlier for eastward travel and later for westward travel.
What is the best way to recover from jet lag after arriving at my destination?
Taking melatonin at bedtime and staying outdoors during the day can help resynchronize your circadian rhythm to local time, while avoiding long naps can prevent further sleep disruption.
How does light exposure affect jet lag recovery?
Strategic light exposure is crucial; for eastward travel, seek morning light and avoid evening light, while for westward travel, seek evening light and avoid morning light to help adjust your body clock.