Does Fasting Help Prevent Jet Lag?

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Airplane food is notoriously unappetizing, yet when that food trolley rolls down the aisle, passengers (even those who were soundly sleeping) perk up. Even if it’s midnight, flyers will happily eat a big meal, just to have something to do to break up the monotony of a long flight. 

A few years ago, I decided to try a controversial travel hack: fasting during flights. I’ve never felt better after eating airplane food, and eating the in-flight meals usually left me feeling thirsty and restless, unable to fall asleep—so why was I bothering with them?

There’s some scientific reasoning behind this method—a 2009 study conducted by researchers at Beth Israel Deaconess Medical Center found that circadian rhythms in mice are strongly influenced by light-dark cycles when food is abundant. However, when food is only available during their normal sleep cycle, the mice shift their circadian rhythms to match food availability.

This finding suggests that for humans, fasting during travel and adjusting your meal schedule to your destination’s local time could help mitigate jet lag. Dr. Clif Saper, the lead scientist on the study, explained to SmarterTravel, “Based on that, I predicted that it might be helpful to limit food before travel, and to eat breakfast at the time when it would occur in the time zone you are traveling to.”

By applying this principle, travelers can ease their transition into new time zones and minimize the effects of jet lag.

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How to Fast on a Long Flight

If I’m traveling on a long flight, I will eat a healthy, high-protein meal (breakfast, lunch, or dinner, depending on the time of day) before I leave for the airport. I won’t eat again until I arrive at my destination, when I will eat a meal that aligns with local time. 

For example, if I’m taking a 10 pm flight from Boston that lands in Paris at 7 am, I will eat dinner in Boston and then fast until I land in Paris. After arriving, I will have breakfast and then follow a normal meal schedule for the rest of the day. I will drink lots of water on the plane to stay hydrated, but I’ll avoid any other beverages in the air, especially alcohol or coffee.

Fasting on flights not only helps with jet lag but also makes me feel better while traveling. At 35,000 feet, reduced oxygen levels in the body slow down digestive enzymes and intestinal motility, making food digestion more challenging. This, combined with changes in cabin pressure that can cause bloating and gas, puts a lot of stress on your body. Additionally, airplane food is notorious for its high salt content, which enhances flavor but can contribute to swelling and digestive issues. By fasting, you give your digestive system a much-needed break.

When I don’t eat on the plane, I find that I feel better upon disembarking, and am more easily able to adjust to the dining schedule at my destination. After a 12-hour fast, you’re likely to be less concerned about whether your next meal should be breakfast, lunch, or dinner—you’re simply ready to eat. As an added bonus, that first post-flight meal tastes exceptionally delicious after a short period of fasting.

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