Avoid obesity…get some sleep!

28Feb08

Well, if you’re a kid that is…

Lack of sleep can increase a child’s risk of becoming obese, according to research scientists at the Johns Hopkins’ Bloomberg School of Public Health, Baltimore.  The investigation, known as a meta-analysis, was published in the February edition of Obesity, the official journal of The Obesity Society. 

Led by Youfa Wang, the scientists reviewed the epidemiological data of 17 published papers, 11 of which they used for statistical analysis.  A significant association was found between sleep deprivation and obesity.  The definite reason for this is not yet fully understood, however, proposals have been made by the research group.  It could be that the lack of sleep results in the child being more tired during waking hours and hence less active, resulting in a reduced amount of energy being used.  It could also simply be that the child is awake for a longer period of time therefore has more opportunities to eat thereby taking in an increased number of calories, over the recommended daily allowance. 

There is some variation in the advice of how much sleep a child needs.  The research group used the recommendations that children under five require at least 11 hours per day, children between the age of five and ten require at least ten hours per day, with children over ten requiring nine hours or more.  They found that those not meeting these targets (i.e.: had two hours below the recommended amount) were at an enormous 92% higher risk of suffering from the disease compared with those that slept for longer.  Furthermore, the risk of a child becoming obese was found to fall by 9% with each additional hour of sleep. 

Wang and his colleagues have considered the possibility of the association have a behavioural basis as opposed to a biological one, with physical performance having more of an influence than internal biochemical processes.  This conclusion was down to the link being significantly higher in boys than girls.  It has been suggested that the ways in which the different sexes spend their late additional waking hours could be what is contributing to the problem, with boys stereotypically playing computer games and hence not very active whereas girls spending more time socialising and generally more energetic.  It must be noted; this suggestion has only been hinted by Wang and does not have any recognised scientific backing. 

Biology, however, must not be completely ruled out.  Certain hormones have in fact been shown to play a role in the process.  Lack of sleep has been associated with lower levels of both leptin and ghrelin, two hormones that influence appetite.  A drop in leptin specifically has been shown in the past to cause an increase in hunger.  

The number of children suffering from obesity is swiftly increasing leading to the threat of a global obesity crisis, especially in the United States where there has been a 3.3% increase in the number of children that are clinically overweight, this only over a five year period.  The obesity epidemic is also a problem in the UK where 1 in 10 six year olds suffer from the ailment and are consequently at risk of some major health problems, such as high blood pressure and Type II diabetes, concurrent with the disease.  Wang made clear how a “desirable sleep behaviour may be an important low cost means for preventing childhood obesity and should be considered in future intervention studies.” 

The Hopkins study also noted that it is not only sleep duration that is important but also sleep quality with the lead author of the paper commenting that with regards to obesity risk it “is another important area where future research is needed.”

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Tags: Health, Johns Hopkins' Bloomberg School of Public Health, Obesity, Sleep