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Adjusting your meal times may help with jet lag, study finds

REUTERS/Lucas Jackson
The findings are interesting — and may have some implications for people who anticipate that their circadian rhythms will soon be disrupted by shiftwork or a plane trip across several time zones.

If you want to minimize jet lag during your next overseas trip, consider changing your eating schedule for a day or two before you get on the plane.

Altering the timing of your meals to match those of your destination can help shift your body’s internal circadian rhythms — specifically the rise and fall of your blood sugar levels — in ways that may ease jet lag, according to a study published last week in the journal Current Biology.

Shift workers may also benefit from the study’s findings.

“It has been shown that regular jet lag and shift work have adverse effects on the body, including metabolic disturbances,” said Jonathan Johnston, the study’s senior author and a chronobiologist at the University of Surrey in Great Britain, in a released statement. “Altering meal times can reset the body clocks regulating sugar metabolism in a drug-free way.”

“This will help us design feeding regimes to reduce the risk of developing health problems such as obesity and cardiovascular disease in people with disturbed circadian rhythms,” he added.

Other studies have found that shift workers are at greater risk of being obese and having related health problems, such as heart disease and type 2 diabetes.

Internal timekeepers

Circadian rhythms are the internal “clocks” that set the timing of the daily rise and fall of blood sugar metabolism and other physiological functions, including body temperature, blood pressure, heart rate and respiration.  

As background information in the study explains, the “master clock” for these internal rhythms is located deep within the brain, in a region known as the superachiasmatic nucleus (SCN). This biological timekeeper is controlled primarily by light-dark cues from the sun.

But there are also “peripheral clocks” located in cells throughout the body. These clocks must be correctly synched to one another and to the outside environment, although they can take a bit longer than the master clock to readjust when the body has a chronobiological shock — such as crossing several time zones within a few hours.

Study set-up and findings

For the current study, Johnston and his colleagues brought 10 healthy volunteers — all young men — into a laboratory for 13 days. The participants were provided with three meals daily, each containing the same number of calories and similar amounts of fat, carbohydrates and protein.

In the initial phase of the study, the first meal of the day was served 30 minutes after each participant woke up, and the other two meals followed at five-hour intervals. In the second phase of the study, the first meal was delayed by five hours, with the other two meals following at five-hour intervals, as before.

After each study phase, the participants underwent 37 hours of a specialized laboratory routine (dim lighting, small hourly snacks, limited physical activity and no sleep) that enabled the researchers to measure, with the aid of blood and fat samples, their circadian rhythms.

An analysis of the data found that delaying the meals by five hours did not affect the participants’ feelings of hunger or sleepiness. Nor did it change the daily rhythms of the hormones melatonin and cortisol, which are both markers of the master clock in the SCN.

The later meal times did, however, delay blood sugar rhythms — by more than five hours, on average.

“We anticipated seeing some delays in rhythms after the late meals, but the size of the change in blood sugar rhythms was surprising,” said Johnston in a second released statement. “It was also surprising that other metabolic rhythms, including blood insulin and triglyceride, did not change.”

The findings about insulin and triglyceride suggest, according to Johnston and his colleagues, that blood sugar circadian rhythms are governed by different internal clocks.

Plenty of caveats

This study comes with caveats. It involved only 10 people — all young, healthy and male — and was conducted in a controlled laboratory setting. The study might have had different results in a “real-world” setting and if it had involved a larger, more diverse group of participants.

Still, the findings are interesting — and may have some implications for people who anticipate that their circadian rhythms will soon be disrupted by shiftwork or a plane trip across several time zones.

Altering the timing of your meals to fit the schedule ahead of you (at your travel destination, for example) rather than the one behind (at your original location) may help your internal rhythms better adjust.

FMI:  You can read the study in full on the Current Biology website

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