Jet lag spent decades in the folklore drawer — melatonin, hydration, grim willpower — while the underlying circadian science quietly matured. The result is a genuine working model: your body clock is entrained mainly by light, on a schedule, with meals and exercise as supporting actors. The protocols follow from the model, and they work better than the folklore.
The model in one paragraph
Deep in the hypothalamus, a cluster of neurons runs a roughly 24-hour cycle, and it resets itself in response to timed light exposure — roughly, morning light advances the clock, evening light delays it. Travel west and your clock must be pushed later; travel east and it must be dragged earlier, which the body resists. Every practical measure either moves the clock or removes obstacles to it.
- Shift sleep 30–60 minutes per day before an eastward trip
- Seek and avoid light on schedule, not on comfort
- Eat on destination time from day one
- Skip the in-flight wine; alcohol fragments the sleep that matters
The protocol, condensed
For eastward trips: shift earlier for several days before departure, get bright light on arrival mornings, and accept that the first afternoon will want to be a nap — keep it short and early. Westward is kinder: stay up later on arrival, avoid bright morning light the first days, let evening light push the clock in the direction it prefers anyway. Melatonin is the one supplement with real evidence, and its direction matters — taken in the local evening it advances the clock, which is exactly what eastbound travellers need.
What does not work
The evidence is unkind to the classics. Homeopathic doses of hydration do nothing the model predicts. “Toughing through” just means spending your trip as a walking clock error. And the strategic long layover nap — the one that feels rational — is usually the anchor that drags your clock home while your body is abroad. Sleep is the output of the clock. Set the clock and the sleep follows.