Love traveling but hate the following jet lag? Then this article is for you.
You are probably aware that long flights crossing several time zones can affect your sleep, something we call jet lag. However, jet lag can actually have more severe health effects and hinder your weight loss. Learn how to best combat this phenomenon.
Jet lag is a phenomenon which can occur when crossing 2 or more time zones during a short time period, like a transatlantic flight.
More acute symptoms of jet lag can include tiredness, insomnia, loss of total sleep time as well as lack of concentration, headache, loss of appetite, irritability, and gastrointestinal symptoms (1).
More long-term effects of frequent traveling with resulting jet lag could possibly result in similar deleterious health effects as shift work. Shift work and jet lag is related in that both disturbs the circadian rhythm. Those negative effects include increased risk of obesity, depression, cancer, hypertension, cognitive impairment, and diabetes (2).
As mentioned above, frequent exposure to jet lag and the negative effects on sleep that follows can potentially hamper your weight loss or even increase the risk of obesity. Sleeping less than 7 h/night is associated with increased prevalence of obesity and higher BMI compared to sleeping 7-8 h/night (3). Sleep or rather inadequate sleep has been shown to have many effects related to weight maintenance, loss and gain, e.g. food intake, energy expenditure, and hunger hormones are affected (3).
In addition, jet lag can possibly also decrease athletic performance, mainly aerobic performance, possibly due to daytime fatigue and sleep deprivation which in turn can cause decreased motivation and impaired cognitive function (1).
Other factors to consider when traveling include loss of fluids due to the dry air in the flight cabin. These fluid losses can result in dehydration and also affect the airways, drying them out (drying and irritating the mucus membrane) and making you more susceptible to pathogens/infections.
Our bodies have an internal clock. Many of our cells have ways of keeping track of time and we also have a center in the brain called the suprachiasmatic nucleus (located in the anterior hypothalamus) that function as a master regulator of our inner clock, synchronizing cellular clocks throughout the body. Our natural rhythm and clock is usually called the circadian rhythm. The circadian rhythm is responsible for our ~24 h daily rhythm as well as many other functions in our bodies. The circadian rhythm can be affected by different factors, for example our environment, especially sun and light exposure.
The circadian rhythm in and of itself is extremely fascinating (The Nobel Prize in Physiology or Medicine 2017 was actually awarded to individuals discovering molecular mechanisms controlling the circadian rhythm) and regulate many bodily functions like core body temperature, hunger, mood, blood pressure, cognitive function, and hormones (e.g. cortisol, melatonin, and insulin sensitivity) (2).
Risk factors for jet lag includes age (middle-aged people, 37-52 years, seems to be most affected but no conclusive evidence exists), number of time zones crossed (more time zones, greater symptoms), west to east travel (eastward travel increases risk), and circadian preference (morning persons going to bed early can fare better on eastward travel while night persons adapt easier to westward travel) (1).
It’s more difficult to adapt to eastward travel and the effects usually last longer (1). This requires a phase advance, going to bed earlier and waking up earlier. The reason why it’s harder to adapt to west → east travel is thought to be due to the fact that the circadian rhythm is slightly longer than 24 h and therefore traveling to a place where you have to phase advance (fall asleep earlier) requires more adaptation (in other words, it requires us to work against our body’s preference to a greater extent) (2).
Usually, two treatment approaches are considered, either symptomatic treatment of the insomnia/sleepiness and speeding the adjustment of the circadian system to the new time zone.
The resynchronization of the circadian rhythm can roughly be expected to have a rate of ~1 time zone per day (1).
Advices to improve the adjustment include keeping a regular sleep-wake schedule, having a good sleep hygiene (dark, cool and quiet environment), avoiding excess alcohol and caffeine, staying hydrated, sleeping as much as possible on the long flights, and eat at the regular meal times for the new destination when arriving to your destination.
When only staying short periods, around 1-2 days, in a new time zone, the goal is not to shift the circadian rhythm but rather to treat the symptoms (sleepiness and increase alertness). This can be done by using sleep medication to fall asleep and caffeine or other alert-enhancing medicines (however, consult your doctor before considering any medications) (2).
When trying to adapt your circadian rhythm to the new time zone, strategies like altering light exposure is preferred.
Light signals to our brains that it’s daytime, and time to be awake. Light before the core body temperature minimum, which usually is around 5 AM (depending on the circadian rhythm of the person), causes a phase delay (i.e. going to bed later). Light after the core body temperature minimum causes a phase advance (waking up earlier) (2).
To adapt faster, one could also start the adjustment before traveling.
For example, for west → east travel, one could start going to bed earlier and earlier (e.g. 30-60 min earlier/day) starting a few days before the travel and also include bright light exposure earlier in the day and limit the exposure closer to bed time.
For east → west travel, a phase delay is the goal. Therefore, going to bed later and light exposure before bed might be a beneficial pre-travel strategies.
Another strategy that can be used is the use of melatonin. Melatonin is a hormone regulating sleep. It is secreted from a gland in our brains (pineal gland) before bedtime and signals sleepiness. Melatonin can be inhibited by light exposure (1) meaning that light exposure close to bedtime could inhibit the normal melatonin production and thereby delay sleep onset. Melatonin can also be taken as medication. Taking melatonin before the core body temperature minimum results in a phase advance (falling asleep earlier) and after the core body temperature minimum results in a phase delay (falling asleep later) (2). Melatonin could be used to adapt to new time zones and combat jet lag but its accessibility differs between countries (some countries sell it OTC some don’t) and therefore timing strategies for melatonin are not suggested in this article.
The symptoms of jet lag should usually have resolved within 2 weeks.
Strategies to speed the adjustment to the new time zone are summarized in table 1 and 2 below.
Fredrik Wernstål is a final year medical student with a passion for nutrition, training, performance and health. His goal is to help people reach a healthier and happier life by providing research-based advice.
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