Why Don’t You Feel Like Eating and Have Sleep Problems After a Long Flight?
Imagine: you’ve just completed a long-awaited flight from London to Tokyo. Outside the window is a bright morning, the city is buzzing, but instead of joy, you feel completely drained. Your head is heavy, thoughts are muddled, your stomach is unsettled, and drowsiness battles with nighttime insomnia. Sound familiar? This is jet lag, or time zone change syndrome.
What is Jet Lag
The term comes from the English words ‘jet’ (jet airplane) and ‘lag’ (delay), and it’s an accurate description of the core problem: your internal biological clock is out of sync with the new rhythm of life you were instantly transported into by the flight.
For travelers crossing multiple time zones, jet lag is more than just discomfort. It’s a physiological revolt by the body, where the usual rhythms of sleep, hormone production, and even digestion suddenly stop aligning with the external world.
Why does this happen? The issue is that our circadian rhythms are a finely tuned mechanism dependent on light, meal times, and social habits. They regulate not only sleep but also body temperature, cortisol production, and digestion. When we “fast-forward” or “rewind” this mechanism by several hours during a flight, the body can’t keep up with the adjustment. The internal conductor then loses control over the orchestra of organs.
Why Jet Lag Occurs
To understand the nature of jet lag, let’s look at the brain. Here, in the hypothalamus, resides the body’s ‘master clock’ — the suprachiasmatic nucleus. It synchronizes our rhythms with the external world through light hitting the retina. When you fly from Lisbon to Singapore, shifting time by +7 hours, the daylight period abruptly shortens or lengthens. The ‘clock’ receives conflicting signals: the eyes see morning, but the body is still living at night.
But there’s a nuance: the direction of travel is critical.
Flying east (e.g., from New York to London) is harder to endure. Here you ‘lose’ time: your body isn’t ready to fall asleep earlier than usual. Imagine: at 10:00 PM local time, your internal clock reads only 3:00 PM. Attempts to fall asleep are doomed — melatonin, the sleep hormone, isn’t being produced yet.
Flying west (e.g., from Tokyo to Los Angeles) is milder. You ‘gain’ hours, and going to bed later is easier than earlier. But there are pitfalls here too: morning light in the new time zone can wake you up at 4:00 AM when your body expects the deep night.
Yes, a three-hour flight from Paris to Dubai (+3 hours difference) might go unnoticed, but a flight to Bangkok (+5 hours) or Sydney (+9 hours) can throw you off track for several days.
How Jet Lag Manifests
Jet lag symptoms are the body’s cry of disorientation. They may resemble the flu or poisoning but have specific characteristics. The first sign is sleep disturbance. In the new time zone, you either suffer from insomnia at night or struggle with sleepiness during the day. For example, after a London-Sydney flight (+10 hours), you might wake up at 2:00 AM local time feeling alert, but by 10:00 AM you’re ready to collapse.
But it doesn’t stop there. The classic triad of symptoms includes:
- Cognitive Impairment: Sluggishness, reduced concentration, memory problems. A simple question like “Where did I leave my passport?” can leave you stumped.
- Emotional Swings: Irritability, apathy, or unexplained anxiety. Physiologists explain this as a disruption in serotonin production — a hormone closely tied to circadian rhythms. For people with chronic conditions (depression, anxiety disorders), jet lag can trigger an exacerbation.
- Gastrointestinal Rebellion: Lack of appetite in the morning and nighttime hunger, constipation, or diarrhea. The culprit is the misalignment of the gut’s function with the new meal times. This is especially pronounced during eastbound flights, where the eating schedule shifts radically.
Primarily, the severity of symptoms depends on the number of time zones crossed. The rule is simple: adaptation takes approximately one day per 1–1.5 time zones. After a New York-Tokyo flight (+13 hours), recovery can take nine to thirteen days.
Young people adapt faster, but the myth of their “invulnerability” is dangerous: a 20-year-old student after an overnight flight can feel just as exhausted as a 60-year-old tourist. Individual characteristics also play a role.
How to Cope With Jet Lag
“Mandry” spoke with a general practitioner.
“Jet lag is real stress for the body, but it’s appropriate to discuss it when changing three to four time zones. When we cross them, especially in an easterly direction, the natural circadian rhythm is severely disrupted. This rhythm regulates not only sleep but also hormonal balance, digestion, and immunity. Melatonin, cortisol, insulin levels — everything falls out of its usual schedule. This can manifest not only as insomnia but also as irritability, weakness, blood pressure fluctuations, and impaired concentration and digestion.”
According to the specialist, here’s how you can help yourself:
- Choose the right flight. For an eastbound flight, a morning departure is better; for westbound, an evening flight.
- Adjust your sleep schedule two to three days before the flight, trying to get closer to the time zone of your destination.
- During the flight, drink enough water (30 ml per 1 kg of body weight), avoid alcohol and caffeine, and avoid fatty and fried foods. Also, try to sleep: a sleep mask and earplugs can help with falling asleep.
- Upon arrival, try to immediately switch to local time, as this will help you start integrating into the new routine.
- A short course of melatonin can help safely adjust your sleep schedule, but any medication should be selected individually in consultation with a doctor.
