In May 2008, a research team from the Beth Israel Deaconess Medical Center in Boston led by the brilliant Dr. Clifford B. Saper published Differential Rescue of Light- and Food-Entrainable Circadian Rhythms, a monumental piece of research delving into the intricacies of our internal body clocks. The team’s research, though performed on mice, shed an enormous amount of light onto how the human body clock works, illustrated perfectly in just two sentences of the paper’s abstract: “When food is plentiful, circadian rhythms of animals are powerfully entrained by the light-dark cycle. However, if animals have access to food only during their normal sleep cycle, they will shift most of their circadian rhythms to match the food availability.” Theirs was a groundbreaking discovery.
The team revealed that in addition to our light-dark cycle, widely known to be the primary driver of our central body clock, another, more powerful body clock takes over when food becomes scarce. When this happens, regardless of light exposure, this food-centric body clock takes precedence over the light-centric one, which means food availability can wield powerful influence over our sleep cycles. In Dr. Saper’s words, “A period of fasting with no food at all for about 16 hours is enough to engage this new clock.” Applying this to a jet lag scenario, wherein travelers need to significantly adjust their master body clock, a shortcut into the heart of our circadian rhythms is an extremely valuable thing. Thus, the 16-hour fast is born.
The 16-hour fast is superior to traditional jet lag remedies for two reasons. First, Dr. Saper's findings point to the effects of food scarcity manifesting significantly more quickly than the effects of the light-dark cycle in regulating our circadian rhythms. While the light-dark cycle change mechanism generally takes several days for our body to gradually adjust to a new time zone, the food scarcity change mechanism provoked by fasting will normally make the adjustment in a single effort.
Second, fasting is more lifestyle friendly. Rather than altering your bedtime for several days leading up to your trip, or carefully managing your exposure to natural light after you land – these being the two most prevalent jet lag remedies suggested today – a single 16-hour fast is enough to make the entire transition at once. When you factor in that you’re probably sleeping for 8 or more of those hours, the 16-hour fast doesn’t seem that bad after all.
One critical component of the 16-hour fast is that you want to time its conclusion with breakfast at your destination, since breaking the fast signals to your body that food is available and, thus, now is the appropriate time to start your day. An example helps illustrate this.
Assume you’re taking the 7-hour flight from New York to Stockholm. You normally eat breakfast at 8am in New York, and your overnight flight lands in Stockholm at 11am. To avoid jet lag in this particular case, you’ll want to conclude your fast at 8am Stockholm time (your regular breakfast time on your destination’s time zone), or 3 hours before you land. This means that you’ll need to fast for the first 4 hours of the flight plus 12 additional hours before that, which works out to a starting time of 10am New York time on the morning that you fly.
As for what you should eat in that first breakfast, don’t overthink it; some protein and a bit of fruits and/or vegetables will do you just fine. Of course, your body will be extra ready to absorb whatever you feed it in this first meal, so keep it as healthy as you can. Drinking water is recommended all throughout the fast, though other beverages – especially caffeine and alcohol – are strictly prohibited since they’ll dehydrate you and reduce or even reverse the fast's benefits.
There you have it: fasting as your new remedy for jet lag. It may make for a slightly less comfortable flight, but when you’re feeling fresh upon landing while everyone around you is struggling to keep both eyes open, you’ll be glad you gave it a try.
For a deeper look into jet lag, including a robust analysis of prevailing remedies, beliefs, and current research, read more on how to beat jet lag here.
