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How Does Sleep Impact Body Composition in Children?

Sleep deprivation is a serious problem in this country, impacting people of all ages. With the advent of cell phones and laptop computers, children are glued to screens almost at all times. This merging of the school and home environment makes it hard for children to stick to a regular bedtime routine. Some kids may even find it hard to fall asleep once they are actually in bed with the blue light that screens put off keeping them awake.

With children taking home large amounts of homework, being kept up by their phones, and having an unprecedented number of extracurricular activities, many children are not getting the proper amount of sleep. When children do not get the right amount of sleep, this can have a negative impact on their growth, development, and overall health.

Recently, the American Academy of Pediatrics released an updated statement discussing the proper amounts of sleep for children by age. Their guidelines indicate that:

  • Babies under 1 year of age should sleep between 12 and 16 hours per day, including naps
  • Infants between 1 and 2 years of age should sleep between 11 and 14 hours per day, including naps
  • Toddlers between the ages of 3 and 5 years need to sleep between 10 and 13 hours per day, including naps
  • Children between the ages of 6 and 12 years should sleep at least 9 hours per night
  • Teenagers need to be getting at least 8 hours of sleep

Even though parents have decent control of when their children go to sleep, their alarms are frequently determined by their school’s starting time. This, plus all of the many distractions in the world today, can lead to children failing to get the recommended amount of sleep. This can cause problems in their school performance but also their physical health.

What is Body Composition?

Body composition is a description of how the different substances in the body are divided. A few examples of the different components that come together to make a human body include:

While some people think of fat as a “negative,” all of these components play an important role in someone’s overall health. Therefore, instead of focusing on pounds gained or lost, focus should be shifted to where change is occurring in terms of body composition, specifically muscle gain or fat loss.

While most people assume that their body composition will only change based on their diet and exercise habits, sleep is a key contributor to maintaining a healthy body composition. The body’s metabolic processes do not stop just because someone is asleep. Therefore, it is important for people of all ages to understand the impact of sleep.

Sleep and Growth Hormone: Important in Children

Growth, in all ages, is primarily controlled by growth hormone. This hormone is regulated by the relationship between the hypothalamus and the pituitary gland, in which sleep plays an important role.

A review article that was published in Comprehensive Physiology showed that:

  • Growth hormone levels peak during the onset of deep sleep
  • Multiple smaller peaks were observed during other stages of sleep
  • Those who have a delay in the onset of deep sleep have delayed peaks in their growth hormone levels

It has long been known that growth hormone levels peak during sleep. For children to grow, they need to have proper levels of growth hormone. This means that children need to have the proper amounts of sleep.

Even in preschool-aged children, sleep is vital for proper body composition. A research study that was published in Obesity measured the body composition of preschool-aged children at the onset of the study and at follow-up one year later. The researchers found that increased levels of sleep resulted in less overall fat mass and therefore a reduced percentage of body fat.

Even though some people associate sleep with laziness and increased adiposity, sleep in children is necessary for a healthy body composition. Children need to make sure that they are getting the proper amounts of sleep to allow their bodies to grow.

Sleep and Muscle Strength in Children

Sleep also plays an important role in muscle building in children. Even though children will build muscle as they run and play, most overlook the importance that sleep plays on muscle hypertrophy and strength.

A study published in the Journal of Sleep Research performed a cross-sectional study examining the sleep habits of close to 1,000 adolescents through a questionnaire. The researchers found that sleep was inversely related to markers of obesity, such as waist circumference, and positively related to skeletal muscle mass in boys.

Interestingly, the adolescents that had the most sleep were affected similarly to those with the least sleep. Both groups showed that waist circumference significantly increased, indicating that both too little and too much sleep can negatively impact body composition.

These results were echoed by another study that was published investigating the sleep habits of college students. While some university students view pulling the “all-nighter” as a rite of passage, researchers found that it can impact their muscle strength significantly.

This study looked at over 10,000 university students and found that males with a short sleep duration (defined as under 6 hours), when compared to those who had a good night’s sleep (more than 7 hours), had reduced muscle strength.

There are lots of reasons why this decrease in muscular strength occurs. For one, as people sleep, protein synthesis increases, allowing people to rebuild the muscle that is broken down over the course of the day. Therefore, it is vital for everyone to get enough sleep to help rebuild their muscle fibers.

Sleep Plays a Direct Role in Obesity

There are more children in the United States who are overweight or obese than ever before. This excess fat tissue leads to the development of numerous health problems including high blood pressure and diabetes. While proper diet and exercise are critical for maintaining a healthy body composition, sleep plays a vital role in the management of obesity as well.

The importance of sleep begins even in the toddler years, based on a study that was published in BMC Public Health. The researchers combined data from close to 70 research articles, totaling close to 150,000 people from almost two dozen different countries. The researchers assessed the sleep of children via parental report or measured the sleep habits directly.

The researchers found that shorter sleep duration led to higher rates of body adiposity in addition to impaired growth, increased screen time, and poor emotional regulation. This means that children who sleep more, even during the toddler years, are more likely to have a favorable body composition, marked by a lower body fat percentage.

These results were backed up by a similar study carried out on children between the ages of 7 and 9, which was published in the American Journal of Human Biology. The researchers performed a cross-sectional study on more than 4,500 children. The height, weight, and skin folds of the children were measured and sleep data were collected via a parent survey. The researchers found that:

  • Children who slept fewer than 9 hours per night was more than three times as likely to be overweight or obese when compared to children who slept greater than 9 hours per night
  • Children who slept more than 11 hours had a body fat percentage of 20.9 when compared to children who slept less than 9 hours, who had a body fat percentage of 23.4 (p < 0.001)

Even though parents might associate more sleep with more sedentary activity, sleep is actually important for children to maintain a healthy body composition. The body needs time to rest and recharge as it gets ready for the next day. Furthermore, the body needs sleep to carry out the growth and development that is critically important to young children.

So, what do all of these studies mean? An article published in Obesity Reviews sought to tie a lot of these results together. The researchers indicated that regular lack of sleep can lead to:

  • Higher levels of insulin resistance, leading to higher cortisol levels, that may eventually lead to the development of diabetes
  • Higher blood pressures and salt retention, linked to cardiac problems
  • The development of diabetes can increase appetite and alter metabolism, leading to changes in body composition and the development of obesity

All of this demonstrates that proper amounts of sleep are vital in the treatment of obesity and excess adiposity. Therefore, any obesity treatment plan should address sleep as a cornerstone to the intervention.

Proper Amounts of Sleep are Crucial to Overall Health

It can be hard for children to get the proper amount of sleep at night. Because of how connected children are today, it is difficult for kids to separate the school environment from home. This leads to challenges in establishing a consistent bedtime routine.

For children, it is vital to make sure that they get to bed at night. Sleep plays a critical role in school performance, social development, growth, and overall health. Even though homework and sports can make it hard for children to get to bed on time, it is important for parents to work hard to keep the bedtime consistent. This means avoiding electronics and exercise prior to bed and staying away from caffeinated drinks such as soda, to keep the body in a regular rhythm. Teaching good sleep habits early can help children to develop properly and maintain health (and a good body composition) into adulthood.

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David Randolph graduated from medical school at the University of North Carolina in Chapel Hill. He is currently completing his Residency in Pediatrics at the University of South Carolina.

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