Authors: Yuri Elkaim
Except when we’re not. The constantly running motor of modern life is much different than what our ancestors experienced 200,000-plus years ago, and with it have come numerous forces that interfere with the way we sync our own internal rhythms with nature. Let’s explore just how you are unsuspectingly disrupting the quality of your sleep.
HOW LIGHT AFFECTS YOUR SLEEP PATTERN
What’s the last thing you did before you went to sleep last night? Can you remember? Odds are you toyed with your phone, watched television, or spent some time staring at a screen. We devote so much of our daily life to screens these days, whether we’re checking our e-mail or texting our loved ones. Unfortunately, if you’re doing this right before bed, you’re also disrupting your natural sleep cycle.
The blue light emitted by the various screens you use so regularly has the same effect as daylight on your circadian rhythm. They both qualify as
zeitgebers
, environmental or external cues that regulate your biological cycles. The alarm clock that screams at you every morning? That’s a zeitgeber. The screeching cats outside your window or even the timing of your meals every day? They’re zeitgebers as well. If you’re fiddling with an app on your phone or watching a television show right up until you hit the hay, its blue light has sent a message to your brain that you’re not ready to sleep. This can make getting to sleep difficult and prevent you from getting a good night of sleep. I’m sure this sounds odd to you, but the effects of blue light are not to be underestimated.
A 2014 study performed at Brigham and Women’s Hospital gathered 12 subjects and instructed six of them to read on an iPad for 4 hours before they went to sleep for 5 nights in a row. The remaining six subjects were instructed to read printed books by dim light for the
same
period of time. The groups switched tasks after a week. The results were quite clear: The researchers observed that those reading on an iPad took longer to fall asleep and also released lower levels of the sleep hormone melatonin. Their melatonin release was delayed by 1 hour, and they reported feeling groggier and sleepier than their book-reading counterparts the next morning. The results remained the same when laptops, cell phones, and some e-readers were used in place of the iPads. Who knew texting or checking Facebook could be so harmful?
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It’s not just the light from your electronic devices that you have to be mindful of, however. Your access to daylight plays a significant role in the consistency of your sleep patterns, as well as your mood and energy. This is light you want to be exposed to as much as possible. It’s perhaps the main reason I enjoy walking with my dogs first thing every morning: It gives me the energy I need for the day ahead and prepares me for a more restful sleep when bedtime rolls around.
A perfect example of light’s impact on your sleep cycle is jet lag. For instance, when I travel from Toronto (Eastern time) to Los Angeles (Pacific time), I gain 3 hours. A 5-hour flight leaving Toronto at 9:00 a.m. means I arrive in Los Angeles at 11:00 a.m. local time (or 2:00 p.m. Eastern time). This is great because I get an extra 3 hours in my day! However, by dinnertime my body is ready for bed. Remember, I normally go to bed around 10:00 p.m., which means 7:00 p.m. in Los Angeles. The next morning is even trickier. If I normally wake up at 5:00 a.m. back home, I could be waking up at 2:00 a.m. in LA.
I’m sure you’ve experienced this time zone conundrum. The first few days can really be uncomfortable. But the cool part is that you can actually speed your adjustment—or readjust your internal circadian clock—by immediately immersing yourself in the local environment. Experienced travelers are quite familiar with this hack: If you arrive in the morning, get outside and take in all that natural sunlight, even if it’s bedtime back home. If you arrive at night, then do your best to wind things down and get ready for bed. Within a few days, your body will have adapted to your new time zone.
I’m
sure this will have you thinking differently about your light intake, but it’s not the only thing that affects the quality of your sleep.
HOW QUANTITY AFFECTS QUALITY OF SLEEP
It’s often said that we should aim for 8 hours of sleep a night. It’s not a strict rule, but it’s a good target. People’s need for sleep varies slightly and lessens as we age. For instance, newborns require the most sleep (12 to 18 hours) because they’re growing and learning at an exponential rate, while most adults require about 7 to 9 hours, based on the latest research from the National Sleep Foundation.
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There’s a sweet spot when it comes to sleep. A University of California, San Diego, study of more than one million adults found that people who live the longest report sleeping for 6 to 7 hours each night.
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Another study of sleep duration and mortality risk in women showed similar results.
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As with exercise, too much of a good thing can definitely be a bad thing. A 2005 study in the journal
Hypertension
found that sleeping more than 7 to 8 hours per night has been consistently associated with increased mortality.
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On the opposite end of the spectrum, getting too little sleep creates a “sleep debt” that must be repaid in the following days; otherwise, you end up living your life in a state of mental and physical fatigue.
Since sleep is a time for repair and recovery, you would think more sleep would be required if your body were hurting or inflamed. At least, that’s my theory, especially considering that when I cleaned up my diet and my body and started taking care of myself, my requirement for sleep greatly diminished. Now, I sleep about 7 hours a night and feel great all day long—no naps required.
Optimal
amount
of sleep is perhaps not as meaningful as the
timing
of that sleep in relation to our circadian rhythm. The research seems to indicate that for adequate and fully restorative sleep to occur, the following two circadian markers must occur after the middle of the sleep episode and before awakening: maximum concentration of the hormone melatonin and minimum core body temperature.
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And, as we’ve learned, this mainly happens at night. Nighttime is also when we’re best able to
reach
the most prized sleep state of all: deep sleep.
Human growth hormone is released during deep sleep, and interruption of this stage abruptly stops its release. As we’ve seen throughout this book, HGH is one of your best friends when it comes to staying lean because it promotes fat loss and improved muscle growth and repair. Deep sleep, intense exercise, and fasting all raise growth hormone in the body. Now you know why all three are important components of the All-Day Fat-Burning Diet.
The shift in and out of deep sleep happens at certain times of the night regardless of when you go to bed. So if you hit the sack very late (like after midnight), your sleep will tilt toward lighter, non-deep sleep (known as REM sleep). And that reduction in deep, restorative sleep may leave you groggy and blunt-minded the next day. Over time, it can also impair your body’s ability to repair and recover, especially if you’re exercising regularly.
In
my college years and when I was playing soccer competitively, I never thought about sleep at all. I wouldn’t mind partying with friends until dawn or sleeping in until noon. I had no regular schedule. Had I known this information back then, I’m sure it would have made a big difference in my performance and how I felt on a day-to-day basis. Now that I’m in my midthirties and much wiser, I’ve realized that sleep is critical for my day-to-day productivity and overall functioning. Plus, with three young boys, the only way I can get stuff done is when they’re out of the house or asleep. In fact, most of the writing of this book occurred between 5:00 and 7:00 a.m. I’m a big believer that the early morning is when our best creativity surfaces, so I’ve built my life around waking up early. It’s a priority for me. Thus, I go to bed between 9:30 and 10:00 p.m. and wake up at 5:00 a.m.—every single day. That’s up to 7.5 hours of sleep.
I would recommend getting to bed before 11:00 p.m. for the best-quality sleep, which means you should naturally wake up earlier as well. And keep in mind that if you’ve taken a nap during the day—especially a longer one that may have tapped into deep sleep—your drive to sleep will be lessened. So work with your body to see what fits. Not every human being is best suited to going to sleep by 10:00 p.m.
LIGHT, SLEEP, AND BODY TEMPERATURE
A 1992 study by the American Physiology Association quickly shifted the sleep schedules of male subjects by 12 hours to accommodate eight or more consecutive simulated night shifts.
In the study, the men were exposed to artificial light of approximately 5,000 lux (a unit of brightness) for 3 to 6 hours each night, slept at home in very dark bedrooms during the day, and wore dark welder’s goggles whenever they went outside during daylight—a 180-degree shift from what their bodies were used to.
Their body temperature was continuously measured, and daily questionnaires provided estimates of sleep time and mood.
What’s fascinating about the results of this study is that the men’s circadian temperature rhythm shifted by approximately 2 hours per day, for a total of a 12- to 16-hour shift by the end of the study. Earlier, I mentioned how low body temperature was a prerequisite for the onset of good sleep. Normally, that happens at night. But this study showed that by looking at artificially bright light at night (when it’s normally supposed to be dark), these men shifted their body temperature from its normal tendency to be low at night to being low at other times of the day.
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WHY SLEEP CONSISTENCY MATTERS
Of all the obstacles to good sleep you’ve learned about in this chapter, this might be the most damaging: not establishing an early and consistent bedtime. It sounds funny, doesn’t it? Bedtime is for kids, right? We adults have so many things to do, and we can’t retire for the night until they’re all done, correct? The answer to that is a firm, undebatable
no
. Sleep consistency is one of the most powerful things you can do to establish and maintain a healthy circadian rhythm.
A 2011 study in the journal
Sleep Medicine
examined the effects of an advanced sleep-wake schedule in 25 adults with typical late-sleep schedules who also had subclinical symptoms of delayed sleep phase disorder (DSPD). That’s a condition in which sufferers have disrupted circadian rhythms, generally fall asleep hours after midnight, and have
difficulty
waking up in the morning. Here, participants were kept on individualized, fixed, advanced 7.5-hour sleep schedules for 6 days. They were exposed to either blue light (group 1) or dim light (group 2) for an hour upon waking each day. The results? After just 6 days, both groups showed significant circadian phase advances, meaning that these 25 adults were now falling asleep earlier and waking more naturally.
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And this was after just 6 days of staying on a fixed sleep schedule!
As for early bedtime, a study from Rush University Medical Center may shed some light (no pun intended) on this question. This study compared the effect of 7 to 19 nights with a late bedtime (1:00 a.m.) versus 7 to 19 nights with an early bedtime (10:00 p.m.) on the body’s melatonin rhythm. Remember, melatonin helps us fall asleep. Each of the subjects was woken (lights on) at 7:00 a.m., then exposed to at least 5 minutes of outdoor light between 7:00 and 8:00 a.m. each day. The researchers found that despite the morning light exposure, the release of melatonin following the late bedtime nights was delayed by almost 45 minutes compared with the early bedtime nights. This suggests that when we truncate our sleep by going to bed later (past 10:00 p.m.), we significantly impair our body’s natural rhythm and melatonin response, which negatively affects our sleep.
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You may think that everything you have to take care of is more important than getting to bed early, but that’s just not true. If anything, by maintaining a consistent, relatively early bedtime, you’ll sleep better and be more productive every day. I assure you of that.
HOW SLEEP SLIMS YOU
By this point, it should be clear that poor sleep isn’t good for you, but that’s not why you bought this book. Let’s address what you’re really concerned about: how all this affects your weight-loss efforts.
Remember, back in
Chapter 1
, we looked at how insufficient or poor-quality sleep is strongly related to weight gain? At a very basic level, sleep deprivation is a big-time stressor on your body. And we’ve seen that chronic stress eventually scares your body into holding on to
weight.
This all goes back to our primal origins, when chronic stress meant starvation or death. Thus, the body is built to hold on to fat as a protective mechanism just in case we run out of food. Yes, I know—this makes absolutely no sense in our modern world, but remember, we’re still using the same operating system that was given to our earliest ancestors.
A fascinating study out of Canada (called the Quebec Family Study) revealed that both short and long sleeping times predict an increased risk of future weight and fat gain in adults. This 6-year study involved 276 adults ages 21 to 64 and looked at changes in adiposity (fat storage) among short-sleeper (5 to 6 hours), average-sleeper (7 to 8 hours), and long-sleeper (9 to 10 hours) groups. After adjustment for age, sex, and baseline body mass index, short-duration sleepers gained 1.98 kilograms (4.3 pounds) more and long-duration sleepers gained 1.58 kilograms (3.5 pounds) more than average-duration sleepers did over 6 years. Short- and long-duration sleepers were also 35 percent and 25 percent more likely, respectively, to experience a 5-kilogram weight gain compared with average-duration sleepers over the 6 years. And the risk of developing obesity was elevated 27 percent for short- and 21 percent for long-duration sleepers compared with average-duration sleepers!
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