New Study Finds Link Between Childhood Obesity and Sleep

By Virginia Gurley | Sep 07, 2010

New Study Finds Link Between Childhood Obesity and Sleep

NPR ran an interesting story this morning on childhood obesity and sleep.  To recap briefly, according to national health surveys, obesity rates have doubled in the past 30 years among children ages 2 to 5 years old and tripled among 6 to 11 year olds in the same time period.  University of Washington researcher Janice Bell recently found that infants and toddlers who slept less than 10 hours each night where twice as likely to become overweight or obese in the following 5 years as infants and toddlers who slept 10 hours or more per night.  The study also found that napping did not provide any protection against becoming overweight or obese.  

The reporter also interviewed the head of Stanford University's Center for Sleep Sciences, Emmanuel Mignot, who discussed the possibility that insufficient sleep in early childhood could cause weight gain and obesity through two hormones that increase appetite, leptin and ghrelin.  As we've discussed previously, studies in adults have shown that a single night of sleep reduction significantly decreases leptin and increases calorie intake by 350 to 500 calories.  Dr. Mignot pointed out that sleep restriction decreases leptin and increases ghrelin both of which increase appetite, especially for carbohydrate rich foods. 

The evidence connecting insufficient sleep with increased appetite and weight gain seems pretty strong.  US national data for all adult age groups shows that as overweight and obesity rates have climbed over the past 30 years, average sleep time has been decreasing steadily.  

As strong as this evidence is, I think sleep is just one factor in a bigger issue.  Sleep is an important signal that helps the body synchronize many physiological functions that occur in a circadian rhythm, ie in a 24 hour cycle.  There are, however, many other behavioral and environmental signals such as sunlight exposure, night time lighting and meal timing that affect circadian physiological coordination of metabolic, cardiovascular and energy balance processes.  

Given the widespread prevalence of erratic meals, high stress levels, insufficient sunlight exposure and significant night time light, my hypothesis is that weight gain and obesity, whether in children or adults, are the result of circadian arrhythmicity.  In other words, the disruption of physiological synchronization of metabolic and energy balance processes is resulting from the loss of numerous rhythmic environmental and behavioral signals that the body has evolved to depend on for coordination and appropriate timing of functions critical to health. 

The timing and duration of sleep are very important to weight balance and health, but I don't think it's just about sleep; it's about too many of the rhythms that support our body clocks, like sunlight, darkness, air temperature, and meal, sleep and activity timing being too diminished or erratic for health sustaining physiologic coordination to occur.   

What Everyone Should Know About How Your Skin Helps You Sleep

By Virginia Gurley | Sep 02, 2010

What Everyone Should Know About How Your Skin Helps You Sleep

Most people are aware of the basic do’s and don’t before bedtime that affect sleep: Do things that are relaxing like taking a warm shower, pleasure reading, listening to music, stretching, or meditating; don’t do things that are stress inducing like exercising strenuously, eating or drinking caffeine, working, thinking or talking about stressful topics.

What is not widely known, and strange as this may sound, the temperature of your skin is critical to being able to fall asleep quickly and stay asleep through the night. Here is what happens and how skin temperature affects your sleep.

  • An hour or two before your typical bedtime, the skin of your hands, arms, legs and feet should start getting significantly warmer due to increased blood flow. 
  • With this increase in skin blood flow and warmth, body heat is given off to the air surrounding the skin, causing your core body temperature to decrease gradually through the night.
  • The increase in skin temperature, along with the parallel night time increase in melatonin, is what causes drowsiness and the rapid onset of sleep when you turn out the lights.
  • When skin blood flow and warming cannot increase due to vasoconstriction (narrowing of the blood vessels), getting to sleep will take longer, staying asleep can be difficult, and how much restorative slow wave sleep and learning-dependent REM sleep you get can be decreased. 

Some things that can cause your blood vessels to narrow when they should be dilating for sleep include high adrenaline levels due to stress, low blood pressure due to dehydration, a medical condition called vasospastic disorder, and a low core body temperature due to eating something very cold like ice cream.

So, here are simple things I do to help my sleep-related skin warming and improve my sleep.

  • If my feet or legs are cool or cold at bedtime, I wear socks to bed and/or take a warm shower.
  • I drink plenty of non-caffeinated beverages during the day and early evening so I am well hydrated by dinner time.
  • When I’ve had a stressful day or feel wound up in the evening, I try to get moderate exercise in the late afternoon or early evening. I use the stress reducing activities described above to help decrease night time stress too.
  • I avoid drinking and eating things that are very cold in the hour before bedtime.
  • I keep the temperature of my bedroom and my bed cool enough that my skin can give off heat, but warm enough that I don’t feel chilled.

If you are familiar with the impact of skin temperature on sleep and have any tips or comments to share, your contribution to exploring this topic is greatly appreciated.

How and when your core body temperature cools at night can also affect your sleep, but I’ll save that topic for a future post.


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