Jet Lag Recovery Depends On Which Way You Fly

Jet lag is worse flying east than flying west, and the direction changes the whole recovery strategy. Flying east asks your body clock to move earlier, which it resists. Flying west asks it to move later, which is easier because your natural clock runs slightly longer than 24 hours. A rough guide is that the body shifts about an hour a day, so several time zones take several days.

Why direction matters so much

Jet lag happens because your internal clock is still set to where you left, while the outside world runs on the new time. Your body wants to sleep, eat and wake on the old schedule.

The direction decides which way your clock has to move. Flying east, you arrive and need to sleep earlier than your body is ready for. Flying west, you need to stay up later, which is closer to what your body would drift toward on its own.

That drift is the key. Left to itself, the human clock tends to run a little longer than 24 hours, so pushing later feels natural and pulling earlier feels like swimming upstream. This is why the same number of time zones hits harder eastbound.

What the research actually says

The core of this is well established, with sensible caveats.

That light shifts the body clock, that the direction of the shift depends on timing, and that eastward travel is generally harder are all supported by circadian research and reflected in clinical guidance on jet lag.

The honest caveats:

• The one-hour-a-day figure is a rough average. People vary, and it is not a precise rule.
• Detailed light timing schedules exist but get complicated fast, and mistimed light can shift you the wrong way.
• Individual chronotype matters. Evening types may cope differently with eastward travel than morning types.

Melatonin is commonly discussed for jet lag, and timing appears to matter more than amount in the research. We do not publish doses or schedules, and it is a conversation for a pharmacist or doctor, particularly with other medication.

Flying east

The harder direction, because you are advancing your clock.

• Shift earlier before you go. In the few days before an eastward trip, going to bed and waking a little earlier gives your clock a head start.
• Seek morning light at the destination. Bright light in the local morning helps pull your clock earlier, which is the direction you need.
• Be cautious with early-morning light in the first day or two after a long eastward flight, since very early light can occasionally shift you the wrong way. Local mid-morning is a safer default.
• Avoid bright light late in the local evening, which would push you later again.

Flying west

The easier direction, because you are delaying your clock, which is closer to its natural drift.

• Stay up to local bedtime. Push through to a normal local night rather than sleeping on arrival.
• Get light in the local evening. Evening light helps hold your clock later, which is the direction you want.
• Get up at a reasonable local time even if you are tired, to anchor to the new schedule.

Advice for any direction

• Switch to local time on arrival, including meals and your watch. Living on the new schedule speeds adjustment.
• Use short naps carefully. A brief nap can take the edge off severe sleepiness, but a long or late one delays adjustment.
• Go easy on alcohol and heavy caffeine, both of which disrupt already fragile sleep.
• Stay hydrated and move, which helps you feel better even though it does not shift the clock itself.
• For very short trips, consider not adjusting at all. If you are somewhere two or three days, staying on home time can beat half-adapting twice.

Common questions

Sources

• National Institute of General Medical Sciences. Circadian rhythms
• Herxheimer A and Petrie KJ. Melatonin for the prevention and treatment of jet lag. Cochrane Database of Systematic Reviews, 2002. Read on PubMed
• National Heart, Lung, and Blood Institute. Sleep deprivation and deficiency
• Centers for Disease Control and Prevention. Sleep and sleep disorders

Keep reading

This article sits in our section on the body clock and timing. The main tool behind it is covered in morning light exposure and better sleep. For the everyday version of the same mismatch, see what social jet lag is. The main sleep guide ties the body clock to the rest of sleep.