Jet Lag Starts When The Internal Is Clock Out Of Sync

Dr. Steven Lockley, chief scientist at Timeshifter and associate professor of medicine in the Division of Sleep Medicine at Harvard Medical School, explained that we all have a central clock in the brain, like the “conductor of the orchestra.”

But most of our organs, the heart, the lungs, the liver, the kidneys, have their own clocks. While all of these clocks can keep time on their own, they still need a “conductor.”

"In a perfect world, you would do the same thing every day, and you would always have the same circadian time," said Dr. Lockley.

But in reality, sleep and meal patterns, social and behavioral factors, and even electric light will slightly disrupt these internal rhythms. He calls these “minor wobbles.”

Larger disruptions ("major wobbles"), such as shift work, late-night weekends and jet lag, could throw our central brain clock more out of sync with the peripheral clocks in our organs.

What Astronauts Can Teach Long-Haul Travelers

Michael Lopez-Alegria, former commander of the International Space Station, explained that space missions generally begin with a two-week quarantine period. During that time, astronauts must adjust their internal clocks to align with a highly specific launch window.

As Lopez-Alegria explained, the guidance includes detailed plans on when to take a nap, when to avoid bright light, when to see bright light, when to drink caffeine and when to avoid it.

The Timeshifter app is based on NASA-linked circadian research, although not connected to or endorsed by NASA itself. Still, it includes these timing-based recommendations in a format travelers can actually use.

"I will tell you it’s extraordinarily effective if you really follow it rigorously and sometimes that’s tough," Lopez-Alegria added.

Mickey Beyer-Clausen, co-founder & CEO at Timeshifter, confirmed that they have collected data from millions of trips and that with increased compliance, the severity of jet lag drops.

"When people follow our advice, 96.4% did not struggle with severe or very severe jet lag. If they didn’t follow the advice, there is a 1,400% increase in severe and very severe jet lag," he added.

Why Light And Melatonin Only Work If You Time Them Right

The standard advice to help jet lag is often to expose yourself to daylight as soon as you arrive, but Dr. Lockley explained that both light and melatonin only work when they are timed correctly.

To explain why, he pointed to the so-called "Phase Response Curve," showing how our clock responds to different cues at different times. The key takeaway is that timing determines whether a strategy helps travelers adjust or pushes them further out of sync.

For instance, exposure to bright light in the morning advances your internal clock (helpful when traveling East), while exposure to bright light late at night delays it (helpful when traveling West).

Melatonin has the exact opposite effect. Taken in the evening, it can shift the clock earlier, while taken later at night or in the morning, it can push the clock later.

That means a mistimed melatonin pill or light exposure at the wrong biological hour will not simply fail to help. It can shift the body clock in the wrong direction, worsening jet lag and exhaustion after landing.

Why Timing Starts Before You Land

The same principle applies in the air, where the timing of the sleep and the cabin conditions should be part of your strategy.

Lopez-Alegria said that because eastbound flights from the U.S. East Coast to Europe are relatively short, so the Timeshifter app generally advises travelers to go to sleep as soon as they board.

Still, he noted that this can be difficult in practice for travelers who want to have a meal, watch a movie or remain awake for part of the flight.

To help with timing, airlines also pay close attention to the onboard environment.

Luke Bondar, COO & president of MileagePlus and vice president of loyalty at United Airlines, said strategic cabin lighting matters not only for visibility.

"When are we dimming the cabin, dimming all the windows, automatically controlled by the crew to create an environment that’s going to be optimal for that flight route," he added.

Meal Timing Matters More Than Most Travelers Realize

Eating during your biological daytime (after 6:00 a.m.) actively delays your liver clock, pushing it later. Eating during your biological night or very early morning (before 6:00 a.m.) advances it.

The takeaway for travelers here is that meal timing must be just as strategic as sleep.

Eating airplane meals simply because they are in front of you, at the wrong biological time, can leave your stomach and liver entirely out of sync with your brain. And we already know that out-of-sync clocks mean prolonged exhaustion and physical discomfort.

From Jet Lag To Longevity

Understanding your circadian rhythm can go beyond managing jet lag. Dr. Lockley also mentioned a study of 60,000 people that found irregular sleep-wake cycles are associated with higher long-term health risks.

"The group who had the most variability in their sleep and light-dark cycles had a much higher mortality rate in an 8-year follow-up," he noted, emphasizing that minimizing any "wobble" in our internal rhythm is critical to longevity.