Jet lag: what works, what does not, and why east is worse

Why the body clock drifts

The human circadian rhythm runs slightly longer than 24 hours in most people - closer to 24.2. Light resets it each day. Left without daylight, people drift later, which is why staying up late is easy and getting up early is not.

This asymmetry is why eastward travel is harder. Flying west lengthens your day, which your body already wants to do. Flying east shortens it, which it resists. A rough rule is one day of adjustment per time zone going east, and rather less going west.

Light is the lever; everything else is minor

Light exposure at the right time shifts the body clock. Light at the wrong time shifts it the wrong way, which is how people accidentally make jet lag last a week.

• Travelling east: seek bright light in the local morning and avoid it in the local evening.
• Travelling west: seek light in the local late afternoon and evening, and avoid bright light early in the morning.
• For large eastward shifts of eight hours or more, get light in the middle of the local day for the first 48 hours, then shift earlier.

A plan that works for most trips

1. Two or three days before departure, shift your bedtime by an hour a day towards the destination.
2. Set your watch to the destination when you board, and start thinking in those terms immediately.
3. Sleep on the plane only if it is night at your destination. Otherwise stay awake.
4. On arrival, get outside. Twenty to thirty minutes of daylight does more than any supplement.
5. Do not nap for more than 20–30 minutes on the first day, and not after mid-afternoon.
6. Go to bed at a plausible local hour - aim for 10pm rather than collapsing at 7pm.
7. Eat at local mealtimes from the first meal. Digestion has its own clock and food helps drag it across.

Melatonin, caffeine and alcohol

Recommendations on melatonin differ by health authority and individual circumstances. Do not choose a dose or schedule from a travel guide; discuss benefits, interactions and suitability with a doctor or pharmacist.

Caffeine can help you stay awake through the first local afternoon, but its half-life is around five hours, so a four o’clock coffee is still working at nine.

Alcohol consistently makes things worse. It may shorten the time to fall asleep but wrecks sleep quality afterwards, and at altitude in a dry cabin it dehydrates you faster.

The flight itself

Cabin air is drier than most deserts, with relative humidity often below 20%. Low pressure and dry air also dull sweet and salty tastes, which is why airline meals are heavily seasoned.

• Drink water steadily. Bring an empty bottle through security and fill it airside.
• Get up and walk every couple of hours. Circulation, not exercise, is the point.
• Use an eye mask and earplugs or noise-cancelling headphones. Controlling light is controlling the clock.
• Wear something you can sleep in and accept that dignity is not the objective.
• Choose a window seat if you intend to sleep and an aisle if you intend to move.

Trips too short to bother

If you are away for two or three days across a large time difference, do not try to adapt fully. Stay on home time as far as your schedule allows, keep important meetings in the overlap, and use light and caffeine tactically.

What does not work

• Fasting for sixteen hours before landing: popular, uncomfortable, and weakly supported.
• Do not start sleeping medication for a flight without medical advice. Benefits, side effects and interactions depend on the medicine and your health.
• Powering through with no sleep: you will crash in the afternoon and wake in the middle of the night, restarting the cycle.
• Special jet-lag diets: meal timing helps, but no specific meal composition has demonstrated a benefit.

Give the first day nothing important

Do not land and go straight into the thing you came for. Give the first day a long walk, simple meal, market and early night - things that are pleasant, outdoors and forgiving if you are operating at 70%.

Plan the itinerary that way and jet lag becomes a mild inconvenience rather than a third of the holiday.