Why Sleep is Important

When people are looking to improve their health, diet and exercise are the first things that come to mind.  But sleep is just as important.  For example, while regular exercise can reduce a woman’s risk of cancer, the benefits may slip away if she gets too little sleep, say US researchers.

“People just don’t realize how important sleep is, and what the health consequences are of not getting a good night’s sleep on a regular basis… Sleep is just as important for overall health as diet and exercise.”

–Carl Hunt, MD, director of the National Center on Sleep Disorders Research at the NIH

Most people need 7-9 hours of sleep per night. 7 should be your baseline.

What influences how much you sleep?

Many things, of course.  Women sleep a bit more than men.  Those who carry high amounts of body fat tend to sleep less than those with a normal body fat.

What you have done during the day will certainly influence how you sleep.  Sleep quality can be poor because of seemingly unrelated lifestyle factors, like weight.  High concentrations of cortisol –- a stress hormone -– can negatively affect sleep quality.  Consuming adequate carbohydrates and protein after exercise can help to control cortisol.

In addition, people might think they're getting enough sleep, but millions of folks over-estimate how much sleep they’re getting.

Most people lose sleep due to voluntary bedtime delay.  We cut back on sleep because we choose to.  We watch TV.  We browse the internet.  We go out with friends.

Lack of sleep usually reflects our priorities rather than real constraints.

Risks of not sleeping enough

Getting fewer than 7 hours of sleep every night can impact your body and your performance in many ways, as well as increases the risk of heart attack, stroke, and sudden cardiac death.

Even though long naps are not recommended, knowing you’ll get to nap during the day can help to lower blood pressure.

Everything from lucid thinking, moods, cognition, and memory, to good decision making, to proper digestion, to body weight and insulin resistance, is heavily dependent on getting good quality sleep.  Feeling bummed out? Get more sleep.  Do you feel sluggish during workouts?  You may be part of the third of adults who get fewer than 7 hours of sleep each night.

Weight gain is linked to inadequate sleep. With the weight gain that could come with minimal sleep, there is then the increased risk of developing insulin resistance (IR), glucose intolerance, and type 2 diabetes.

And age and overall health does not mitigate the risk: Eleven healthy men in their 20s were only allowed 4 hours of sleep for six straight nights. At the end of this, the young men had the insulin sensitivity of a 70 year old pre-diabetic! Despite the small sample size in this study, the results are suggestive.

Going 24 hours without sleep is similar to performing with a blood alcohol level of 0.10%.

Sleep debt is cumulative, meaning that the more nights with less sleep, the greater likelihood of negative effects taking place.  The good news is that you can catch up with just a few consecutive nights of adequate sleep.  Experts hypothesize that each hour of sleep debt needs to be repaid, eventually.

Weight and sleep

Studies suggest that people who sleep fewer than 6 hours per night gain almost twice as much weight over a 6-year period as people who sleep 7 to 8 hours per night.  Excessive sleep isn’t necessarily better: those who sleep more than 9 hours per night have similar body composition outcomes as those who sleep less than 6 hours.

Another study found that people between the ages of 32 and 49 who slept fewer than 7 hours each night were significantly more likely to be obese.  Similarly, a study that followed the growth of more than 9,000 children from birth onwards showed that children who slept the least when they were 30 months old were more likely to be obese at age 7 than children who slept more.

Are you starting to see the link here?  However, it is not clear yet whether poor sleep is a cause or a result of excess body fat (or both).   It is possible that the physical discomfort of obesity and sleep apnea could reduce the chances of getting a good night’s sleep.

Have you ever had a night where you slept only a few hours, and the next day, in addition to not thinking clearly, you also seemed hungry all day?  There is a reason for that.  Insufficient sleep disrupts up the appetite hormones.  When you've had too little sleep, your body will make MORE of the hormone that makes you hungry, and LESS of the hormone that makes you feel sated.  The body craves energy dense food, things like sweets, baked goods and bread.  Unfortunately, healthy vegetables are not energy dense, so there is no craving for them…

While there are many reasons that lack of sleep could influence body fat, this hormone disruption could be one of them.  Other hormones disruptions are: decreased growth hormone (GH), thyroid stimulating hormone (TSH), and increased cortisol, most notably in the evening.  Even though the sleep deficit occurred 12-ish hours ago, the whole day is disrupted.

Moreover, chronic sleep restriction results in elevated sympathetic nerve activity and a slow insulin response.  This is the perfect storm of side effects to contribute to obesity:

  • Lowered glucose tolerance (GT)
  • Increased evening and nocturnal cortisol levels
  • Lowered leptin (Leptin is a hormone that makes you feel full so you stop eating)
  • Insufficient thyroid stimulating hormone (TSH)

In addition to all this, practically speaking, lack of sleep may contribute to obesity because more time spent not sleeping means more time to eat. And those fast food commercials start looking pretty appealing at 1 a.m… Taco Bell is open 24 hours … (I think??)

How late is too late?

All of these risks related to sleep deprivation have a “dose-response” relationship, with later bedtimes and shorter sleeping hours resulting in greater levels of body fat gain.  While wake-up time was not significantly related to obesity, staying awake beyond midnight seemed to increase the likelihood of obesity.  According to some sleep experts, because of the way our natural circadian rhythms work, every hour of sleep before midnight is worth two hours after.

Sleep stages

Five stages occur during sleep.  Light sleep occurs during stages one and two, while stages three and four are deep sleep.  Rapid-eye movement (REM) sleep, generally when dreaming occurs, takes place during stage five. A full cycle through these five stages occurs about every 90 minutes.  If numerous full cycles of sleep aren’t attained most nights, mental restoration can diminish.


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