How to beat jet lag and reset your body clock faster

Crossing more than three time zones is the threshold the CDC uses for the kind of travel that usually triggers jet lag. Jet lag hits when your normal sleep pattern is out of sync with a new time zone, and it can spill into mood, concentration, and physical and mental performance. It usually improves within a few days as your body adjusts.

Before you fly: start shifting the clock early

The most common mistake is waiting until takeoff to think about jet lag. Get plenty of rest before travel and begin going to bed and getting up earlier or later than usual so your schedule moves closer to the destination time zone. That advice matters most on longer trips.

If you are flying west to east, go to bed earlier than usual and avoid bright light before bedtime. The main treatment for jet lag is timed light exposure, and light is one of the strongest signals for shifting circadian rhythm. Harvard Medical School’s sleep program sets out a more specific rule for faster adjustment: avoid bright sunlight for at least five hours, then seek light after 11 a.m.

Meal timing may also help. Research highlighted by UCLA Health suggests jet lag can be managed with food schedules, and timing meals on the day you fly may make a difference. In controlled lab studies at Harvard, volunteers lived on 28-hour cycles in a windowless, soundproof space while researchers tracked glucose, insulin, and other measures, showing how closely the body’s metabolism follows timing cues as well as sleep.

A short fast has also been studied as a possible reset tool. In a 2016 Harvard Health discussion, Dr. Charles Saper suggested a 12-to-16-hour fast before and during travel as a way to trigger a quick circadian reset.

On the flight: protect sleep, hydration, and movement

Once you are on board, drink plenty of water, keep active by stretching and walking around the cabin, and try to sleep if it is nighttime at your destination. Long-haul flights can leave you dehydrated, stiff, and already more out of sync with local time by the time you land.

The key is not to treat every flight as a chance to sleep as much as possible. If the clock at your destination says it is nighttime, sleeping on the plane supports the new schedule. If it is daytime where you are headed, staying awake and using the flight to ease into the new rhythm can make the landing less punishing.

Movement matters here because it keeps you more comfortable physically and helps prevent the plane from becoming a long, passive extension of bedtime. Even small routines, like standing up regularly and stretching in place, keep you active during the flight.

The first 48 hours after landing: use light as your reset button

The first two days after arrival are where timing matters most. Timed light exposure is the main treatment for jet lag, and Harvard Medical School’s guidance is specific enough to use as a travel plan: avoid bright sunlight for at least five hours, then seek light after 11 a.m. That kind of timing gives your body clearer signals about when the new day starts.

If you have crossed time zones eastward, the strategy is usually to advance your sleep earlier. That means getting to bed at the destination’s local bedtime, avoiding bright light before bed, and using morning daylight to anchor the new schedule. Jet lag is a mismatch between your daily rhythm and the new time zone, so the goal is to give your brain the right cues as quickly as possible.

Food timing can reinforce that reset. Meals on the day you fly may matter, and the broader Harvard research on glucose and insulin shows why: when eating lines up with the body clock, metabolism tends to behave better. For many travelers, that means eating at local times as soon as possible instead of snacking randomly across the clock.

Melatonin: useful for some travelers, but not the first lever

Melatonin is a natural hormone that helps control the sleep cycle. The body makes it just after dark, it peaks in the early hours of the morning, and it falls during daylight.

Melatonin tablets can help people get to sleep and improve sleep quality. For short-term sleep problems in adults, the NHS lists the usual dose as one 2mg slow-release tablet taken 1 to 2 hours before bedtime. That can make melatonin useful when you are trying to shift your sleep timing after travel, but it works best as part of the bigger plan: light in the right place, sleep at the right local time, and a schedule that supports the new time zone.