You know the feeling. You land, you function, you get through the meeting, and something is still running half a beat behind. Hunger arrives at the wrong times. Sleep feels impossible at 3am and unavoidable at noon. This is not simply tiredness. It is your biology keeping the wrong time.
The encouraging part is that the system is modifiable. By pulling on the right levers at the right time, you can actively accelerate the transition towards the new time zone, and maintain your health and performance while you travel.
Your body runs on an internal timing system that coordinates sleep, hormone release, body temperature and metabolism across the roughly 24 hour cycle. At its centre is the suprachiasmatic nucleus, or SCN, a small cluster of cells in the brain that acts as the master clock. It is set primarily by light. As darkness falls, the brain releases melatonin, the body's clearest signal that biological night has arrived. As morning light reaches the eyes, melatonin production is suppressed and the body transitions towards wakefulness. When that signal is disrupted, sleep, alertness, focus and mood can all temporarily fall out of step.1
Travel creates exactly this problem. You can arrive somewhere at 8am, while your brain and body still behave as though it is 1am. As a rule of thumb, it takes roughly one day per hour of time zone change for the master clock to resynchronise to the new environment, which means a 6-hour jump can leave you working below your peak for the better part of a week if you do nothing to help it adapt.2 This adjustment is typically faster flying westwards than eastwards. That is because your body clock runs slightly longer than 24 hours, so it drifts later each day by default. Flying west moves with that drift, while flying east goes against it. Plan for eastward travel to cost you more.
And the disruption is not confined to the brain. Every major organ keeps its own cellular clock, and these peripheral clocks shift at different speeds. The result is a kind of internal chaos: while your master clock is still aligned to the place you left, the gut, liver and kidneys arrive at their own pace. That shows up as hunger at odd hours, bloating, and bathroom habits off schedule, in addition to the expected broken sleep and patchy concentration.
Time zone maths is only part of the story. A flight taxes the body on its own, so even a small time zone shift can leave you feeling flat when the journey is long. The same systems are also unsettled by weekend late nights and lie-ins that nudge your clock off schedule. In addition to resetting the clock, the strategies in this issue help with that broader travel load and changing schedules too.
How you feel at any moment is a conversation between systems, and recalibrating after travel takes more than fixing sleep alone. Three levers move the clock, and timing gives each its direction.
Your brain is wired to take its strongest timing cue from light, which makes daylight your primary lever for resetting the clock. Morning daylight is vastly brighter than typical indoor light, rich in the short blue wavelengths the clock responds to, and early exposure makes it a powerful signal for shifting the master clock. As the sun drops, evening light turns dim and long in wavelength, allowing melatonin production to begin shortly after. Conveniently, the clock responds to short bursts, so even a brief trip outside on a cloudy morning in your new destination provides a meaningful signal.3 The same principles can work against you in the evening, when bright screens suppress melatonin and push the clock later. One insight from the MELOS coaching room that catches most members out: after an eastward arrival, if you wake at 3 or 4am and cannot get back to sleep, keep the lights low until about 6am. Bright light before your temperature minimum, the coldest point of your night, pushes the clock later when you are trying to pull it earlier.
A moderate training session raises core temperature, circulation and alertness, anchoring you to the new schedule and preventing the mid-afternoon dip. As with light, timing sets the direction: morning and early afternoon exercise moves the clock earlier, evening exercise moves it later.4 Temperature also explains an apparent contradiction. Exercising close to bedtime raises core temperature and disrupts sleep, whereas a warm bath 1 to 2 hours before bed promotes it, because warming the skin increases circulation and accelerates heat loss after the bath, so core temperature falls.5 That fall is part of the body's normal transition towards sleep, which helps explain why a cool, dark bedroom is so effective. In the first day or two after a long shift, exercise to feel better rather than to test your limits; reaction time and fine decision-making are the last things to come back.
Meal timing is one of the strongest signals available to the peripheral clocks in the liver and gut, which coordinate digestion, blood sugar balance, metabolism and energy. Near biological night, rising melatonin changes insulin release, so the same meal eaten late produces a larger glucose response than it would earlier in the day. Used deliberately, this becomes a tool: land in the morning and a generous breakfast reinforces that the day has begun; land in the evening and a lighter, lower carbohydrate meal keeps the signal pointing towards night.6 From the moment you board, set your watch to destination time and let it guide when you eat, seek light, move and sleep.
Digestive trouble is often the first thing to feel wrong in a new time zone, and there is a reason. Your gut microbes run on their own daily rhythm, set largely by when you eat, and travel shifts your schedule faster than those microbes can adapt.7 Combined with altitude, where lower cabin pressure expands the gas already in your gut, bloating is common. This is called gut jet lag, and it can be managed.
Keep the same number of meals as at home, on destination time, and plan them before you travel rather than deciding while tired in transit. Never trial a new food on flight day. The night before you fly, limit fried food, spicy sauces, stimulant foods and alcohol, and finish dinner 2.5 to 3 hours before sleep. On journeys up to about 4 hours, consider flying fasted, since eating in the air worsens bloating. We tend to start a travel-specific multibiotic before departure to address regularity. Disruption to microbial rhythm is well documented, but current trial data on managing it is limited. So this comes from years of clinical experience, and what we see is better digestive resilience across the trip.
Used well, caffeine is one of the better tools for boosting alertness during the shift, a way to prop up the daytime signal when your body wants to sleep at the wrong hour. The timing is what makes it work for you rather than against you. From boarding, run caffeine on destination time, and drink the last cup around 8 hours before destination bedtime. Caffeine inside that window measurably shortens and fragments sleep even when you fall asleep normally. On board, remember cabin air also dehydrates, and both caffeine and alcohol contribute to fluid loss. Water, herbal tea and an electrolyte sachet are the small choices that pay off on arrival.
Supplemental melatonin is a timing signal, not a sleeping pill. Your body releases it naturally as light fades to signal that biological night has arrived. A well timed dose can send that same message to a body clock still operating in the wrong time zone. In the UK, melatonin is prescription only, which makes it a conversation for your clinical team and not an airport pharmacy.
When correctly timed, a low dose of 0.5mg can shift the body clock as effectively as a 3mg dose, while higher doses of 5mg and above may increase grogginess and vivid dreams.8 It works best across distance, with a paper finding it effective for jet lag when travelling across a time difference of 5 hours or more, taken close to destination bedtime.9 Sourcing the right kind, with appropriate certifications, matters too, since analysis of commercial melatonin found content ranging from a fraction of the stated dose to several times the label.10
This section turns the science into action. The aim is to understand which signals your body needs, then use them deliberately as you move between time zones. The further you travel, the more useful this framework becomes.
For eastward trips, shift sleep and wake 30 to 60 minutes a day towards the destination across the 2 to 3 days before you fly, pairing the earlier wake with morning daylight. Plan your flight and arrival meals now. Start the travel multibiotic. The aim is to shrink the biological jump you are asking the body to make.
Set your watch to destination time from boarding. Flying east into a destination night, keep light low with an eye mask and dim screens. Flying west into a destination afternoon, seek light later in the flight. Move every hour or two. Eat lightly or not at all on short sectors, and hydrate with intent.
Get outside when light supports the direction you are shifting, removing sunglasses for that window. Morning landing, a proper breakfast, and consider some movement. Evening landing, a lighter, lower carbohydrate meal, then darkness and an early night.
Consistent local wake time, light at the right time, meals on local time, movement during the day. If a nap is needed, limit it to about 20 minutes, and only when more than 8 hours remain before local bedtime. Longer or later naps delay adaptation.
Electrolyte sachets in an adjusted low dose, compression socks, an eye mask and earplugs, blue light blocking glasses from sunset, and for some members micro nerve stimulators for the legs.
Jet lag is a temporary mismatch between your internal clock and the environment around you, and the fastest way to adapt is to give your biology a coherent sequence of cues, at the right time. Light tells the clock where day begins, darkness signals night, food aligns the peripheral clocks, movement reinforces the daytime signal, and sleep consolidates the shift. None of this needs to run as a rigid protocol. Once you understand which signals your body is looking for, and which matter most for you, applying them becomes second nature, and the familiar drag of jet lag becomes a distant memory. These recommendations also extend beyond long-haul travel. A short flight, or even the drift of a late weekend, pushes your sleep, meals and light exposure out of their usual order, which affects the same systems whether or not the clock has to move. Understood this way, travel becomes something you manage on your own terms rather than something you recover from. The goal is to arrive ready to perform, and feel good doing it.
On your next trip, which single signal, light, meals or caffeine, are you still sending at the old time zone's hours, and what would it take to move just that one?
Shared with you by MELOS · Your health actively managed