Quick answer: Jet lag is not tiredness, and sleeping more will not fix it. It is your body clock pointing at the wrong time, and the only reliable lever is light — specifically, getting bright light at the right end of the day and deliberately avoiding it at the wrong end. Get the direction wrong and you will actively make it worse. For most India-to-Southeast-Asia trips it is not even a factor; what you are feeling there is a 4am departure.
Almost every jet lag article gives you the same six tips: drink water, avoid alcohol, get some sleep on the plane. These are fine and they do approximately nothing, because they treat jet lag as a fatigue problem.
It is not. It is a timing problem. Your internal clock is still running Indian Standard Time in a country where the sun is doing something else, and no amount of hydration moves a clock.
What does move it is light. Here is how to use it properly.
Why Flying East Is Worse
The human circadian clock, left to itself in a cave with no light cues, runs slightly longer than 24 hours. That means your body finds it easier to stretch a day than to shorten one.
Flying west — Delhi to London, New York, San Francisco — you need to delay your clock. Stay up later. Your body is already inclined that way.
Flying east — Delhi to Tokyo, Seoul, Sydney — you need to advance your clock. Go to sleep earlier than your body wants to. This is the hard direction.
Roughly three-quarters of people find eastward travel worse. The rough clinical heuristic is about one day of recovery per time zone travelling east, and one day per one-and-a-half zones travelling west — though this is a rule of thumb, not a finding, and individual variation is large.
Jet lag generally starts to matter from about three time zones onward. Below that, you are dealing with something else.
The One Thing That Actually Works: Light, at the Right Time
The technical version involves your core body temperature minimum, or Tmin. The practical version is simpler than it sounds.
Estimate your Tmin as roughly three hours before your normal wake-up time, in home time. If you usually wake at 7am IST, your Tmin is around 4am IST. That is your pivot point, and it travels with you.
Then apply the rule for your direction:
Direction | Seek bright light | Avoid bright light |
|---|---|---|
Eastward (need to advance) | In the ~4 hours after your Tmin | In the ~4 hours before your Tmin |
Westward (need to delay) | In the ~4 hours before your Tmin | In the ~4 hours after your Tmin |
Translated into what you actually do:
Landing in Tokyo (eastward): get outside in the destination morning. Wear sunglasses if you are up in the very early destination hours for the first day or two.
Landing in London or New York (westward): get late-afternoon and evening light. Avoid bright early-morning destination light for the first couple of days. Do not nap at 5pm.
You can shift your clock by roughly an hour a day advancing and up to two hours a day delaying. And your Tmin moves as you adjust, so recompute it each day.
The single most common self-inflicted mistake: getting bright light at the wrong end of the curve. An eastbound traveller who goes for a sunrise walk on day one before their Tmin has passed is pushing their clock the wrong way. Doing nothing would have been better.
Melatonin: What the Evidence Says
Melatonin has the strongest evidence base of anything in this article, and it is routinely used wrong.
The Cochrane review on melatonin for jet lag found it effective for preventing and reducing jet lag, with eight of ten trials positive and a number-needed-to-treat of about two — which is a strong result by the standards of travel interventions.
Key findings from that evidence base:
Doses between 0.5 mg and 5 mg were similarly effective for jet lag. Higher than 5 mg added nothing.
Timing is the active ingredient. Taken close to target bedtime at the destination, roughly 10pm to midnight local. Taken during the day it causes counterproductive sleepiness and can shift the clock the wrong way.
The strongest recommendation is for eastbound flights crossing five or more time zones.
Evidence that melatonin adds much to bright-light-driven westward adjustment is not established.
There is also a distinct chronobiology protocol where a small dose — around 0.5 mg — is taken about ten hours before Tmin, in the afternoon, specifically to shift the clock rather than to induce sleep. That is a different use of the same molecule, and it is easy to conflate the two.
Cautions worth taking seriously: interactions have been flagged with anticoagulants such as warfarin, and there are concerns around epilepsy. Supplement purity and actual dose accuracy vary widely worldwide. If you are pregnant, on regular medication, or have an existing sleep disorder, ask a doctor rather than a travel blog.
Melatonin's regulatory status in India — whether it requires a prescription — is worth confirming with a pharmacist rather than assuming, as it is regulated as a drug rather than as a food supplement.
What About the Jet Lag Diet?
The Argonne Anti-Jet-Lag Diet, developed at Argonne National Laboratory in the 1980s, alternates feast and fast days with carefully timed caffeine. One military field study across nine time zones reported benefit, and it has circulated ever since.
The honest assessment: the evidence is weak. There is no robust modern trial support, the protocol is elaborate enough that almost nobody follows it correctly, and its caffeine component confounds the result.
The underlying biology is real — meal timing genuinely is a time cue for peripheral clocks in the liver and gut. But it is secondary to light for the master clock, and human evidence that meal timing shifts the central clock is limited.
Eating breakfast on destination time is sensible and harmless. It is not the mechanism.
Caffeine and Alcohol
Caffeine improves alertness during destination daytime and can modestly delay the clock. It does not speed adaptation. Keep it out of the six to eight hours before your target bedtime.
Alcohol degrades sleep architecture, suppresses REM and fragments the second half of the night, on top of dehydrating you. The two glasses of wine to "sleep through the flight" tactic is counterproductive — you will be unconscious, not asleep.
Route by Route, From India
Route | Shift | What to expect |
|---|---|---|
Southeast Asia | +1.5 to +2.5 hrs | Not jet lag. Below the three-zone threshold |
Gulf | About −1.5 hrs | Negligible |
Japan, Korea | +3.5 to +4 hrs | Mild eastward, 2–3 days |
Australia east coast | +4.5 to +5.5 hrs | Moderate eastward, melatonin's best case |
Europe | −3.5 to −4.5 hrs | Westward, 2–3 days |
UK | −4.5 to −5.5 hrs | Westward, 2–3 days |
US East Coast | −9.5 to −10.5 hrs | Hardest common route, a week or more |
US West Coast | −12.5 to −13.5 hrs | Near day-night inversion |
Two of these deserve expanding.
Southeast Asia is not a jet lag problem. Bangkok, Singapore, Bali and KL are all inside two and a half hours of IST. What you feel on arrival is the consequence of a departure bank that clusters between 3am and 6am out of Indian metros. That is sleep debt, and the fix is sleeping, not light therapy.
The US East Coast is the genuinely hard one because a ten-hour shift sits close to the point where advancing and delaying are equivalent. Most people do better treating it as a delay — evening light, late bedtime — because delaying is biologically easier. The important thing is to pick one strategy and hold it rather than oscillating.
The Red-Eye Playbook From India
Westbound (Europe, Gulf, US via a Gulf hub). Departures cluster between 1am and 4am IST. You board already sleep-deprived. Sleep the first block of the flight, then stay awake through the arrival day. Get afternoon light. Go to bed at a local hour. Do not nap on arrival beyond twenty or thirty minutes — the 5pm nap is what ruins the first three days.
Eastbound (Southeast and East Asia). Departures cluster between 3am and 6am IST, arriving around midday. This is a sleep-loss problem, not a circadian one. Sleep freely on the plane, then get destination morning light the next day.
The underused move: shift before you fly. Moving your bedtime an hour earlier per day for two or three days before an eastbound trip, with morning bright light, measurably reduces arrival jet lag. It costs nothing and almost nobody does it.
Key Takeaways
Jet lag is a clock alignment problem, not a tiredness problem.
Estimate Tmin as three hours before your normal wake time. Seek light after it going east, before it going west.
Getting light at the wrong time makes it worse than doing nothing.
Melatonin has real evidence at 0.5 to 5 mg taken at destination bedtime, best for eastbound flights of five or more time zones. Higher doses add nothing.
Southeast Asia does not cause jet lag — the 4am departure does.
Pre-shifting your bedtime for two or three days before an eastbound flight is the highest-return, least-used tactic here.
How long does jet lag actually last?
Commonly a few days, occasionally a couple of weeks on the biggest shifts. The one-day-per-time-zone rule is a rough guide, and age, chronotype and direction sensitivity all change it.
Does business class help?
It helps the fatigue, not the clock. Arriving rested is genuinely better, but a flat bed does not move your circadian rhythm — light does.
Do jet lag apps work?
The good ones implement the light-timing protocol described above and do the Tmin arithmetic for you, which is their real value. Check that the app is asking about your normal wake time; if it is not, it is guessing.
What about very short trips?
For a two or three day trip crossing many zones, the standard advice is to not adjust at all — stay on home time as far as your schedule permits. Half-adapting twice is the worst of both.
This is general information, not medical advice. The light-timing and melatonin protocols described here come from published sleep research, but individual response varies substantially. Anyone with epilepsy, on anticoagulants, pregnant, or with a diagnosed sleep disorder should speak to a doctor before using melatonin. Melatonin's prescription status in India should be confirmed with a pharmacist. Last checked against public sources in August 2026.
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