Health & Fitness

Bumpy & Bulky: The Science of Jet Lag and Body Weight

Many of us have had this experience: boarding a plane, landing some hours later in a different time zone, and feeling exhausted while everyone around us seems energized and ready to go. What we’re experiencing is jet lag, of course, and is defined by WebMD as the rapid crossing of two or more time zones accompanied by symptoms of sleepiness and sluggishness.

What causes jet lag? According to Camille Peri of WebMD, jet lag is the result of an abnormal circadian rhythm induced by high-speed travel. Our circadian rhythm is sort of like an internal clock, regulated by external cues such as mealtimes and exposure to light. Dr. Allison T. Siebern, a fellow in the Insomnia and Behavioral Sleep Medicine Program at the Stanford University Sleep Medicine Center, explains how this clock can be thrown out-of-whack: “When you cross time zones, it disrupts those [cues], and your internal clock and the external time are desynchronized. Your body needs to get on the rhythm of the new time zone.”

A new study done by a team at the Stanford University School of Medicine, recently reported by DailyMail, found a link between jet lag and weight gain. Specifically, increases in body fat content are related to stress and poor sleep, two phenomena that are characteristic of jet lag. According to Dr. Mary Teruel, lead author and Assistant Professor of Chemical and Systems Biology, “If you experience chronic, continuous stress…the resulting loss of normal circadian glucocorticoid oscillations will result in significant weight gain.” In other words, an out-of-whack circadian rhythm disrupts the normal hormonal cycle, thus harming physical health and fitness. Furthermore, the study showed that the buildup of unhealthy fat due to such stress is especially prominent in the belly area.

Hold on a second. Stress. Sleep deprivation. Sluggishness. This reminds you of college life, doesn’t it? Well, I’ve got bad news: according to the Stanford study, spikes in the stress hormone cortisol during sleep hours can disrupt your body’s fat balance. The resulting imbalance, in turn, causes the body to convert precursor fat cells into actual fat cells. These effects seem to confine themselves to the nighttime, however. According to Dr. Teruel, “Even if you get significantly stressed…you won’t gain weight, as long as stress…happens only during the day.”

It’s important to note that not all increases in cortisol levels are bad. Dr. Teruel and her team found that increases in cortisol levels are beneficial if they happen during the day and for a duration of fewer than 12 hours. This increase helps the breakdown of stored fat into glucose, boosting our energy in the process. This is partly why an afternoon workout—which will temporarily increase cortisol level—is good for the body. Cortisol hikes are detrimental when caused by chronic stress. They are detrimental at night, and especially so if they last for more than 24 hours. So much glucose is produced that the body can’t use it all up, eventually causing an accumulation of unhealthy body fat.

So, are there any ways to fight off jet lag? You bet. The National Sleep Foundation makes a few suggestions about ways to change how you travel, en route to alleviating the symptoms of jet lag and decreasing the amount of stress put on your body. As a few examples, the Foundation recommends booking a flight that arrives in the early evening (local time). In addition, several days before traveling east, you should start going to bed earlier than usual. (Vice versa if you’re traveling west.) And finally, both prior to and after arrival, you should avoid caffeine during the three to four hours before you go to bed.

Sometimes, we have no choice but to travel. We miss our families. We need to go to college. We need to visit some friends. Rapid travel might be inevitable, but the detrimental effects of such excursions certainly are not.

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