You lose one day per hour of time difference if you do nothing. Most of that is recoverable with three unglamorous habits, and none of them are the ones sold at the airport pharmacy.
What jet lag actually is
Your body clock runs on roughly 24 hours and is set primarily by light hitting your eyes, secondarily by meal timing. Fly six time zones east and your internal clock still thinks it is 3 a.m. It re-syncs at about one hour per day on its own — or two to three times faster if you feed it the right signals.
Eastward travel is harder than westward, because going east asks you to fall asleep early, and nobody can do that on command. Going west asks you to stay up late, which everyone can do.
The three things that work
1. Light, at the right end of the day
Flying east (Europe, Asia): get bright morning light on arrival day and avoid dim afternoons indoors. Flying west (back to North America): get evening light and skip the early sunrise walk. This is the single most powerful lever, and it is free.
2. Sleep on the plane only if it is night where you are going
An overnight flight to Europe leaves at 6 p.m. and you should try to sleep as soon as dinner is done. A midday flight to Asia is not bedtime anywhere — stay up, then sleep on the local schedule when you land.
3. Eat on destination time from the first meal
Meal timing is a secondary clock signal and it is easy to control. Skip the airline breakfast served at 3 a.m. destination time. Eat when the people around you at your destination are eating.
The things that half-work
Melatonin has decent evidence for eastward travel, at a low dose (0.5–3 mg) taken about an hour before your target bedtime for the first three nights. It is a clock signal, not a sedative, and more is not better. Ask your doctor first.
Caffeine is useful before 2 p.m. local time and counterproductive after. Naps are fine at 20–30 minutes and destructive at two hours.
The things that do not work
Alcohol on the plane — it fragments the sleep you do get. Fasting protocols that require 16 hours of misery for a marginal gain. Any wristband, spray or patch sold at duty free.
What we build into trips
Nothing scheduled on arrival day, ever. A late start on day two. And on long-haul departures, we push the welcome dinner to a normal local dinner hour rather than an early one, because staying up until 10 p.m. local time on night one buys you the whole rest of the trip.
