Exercise as it relates to Disease/The effects of increased screen time on childhood obesity

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This Wikibooks page is an analysis of the research article "Relationship of Physical Activity and Television Watching With Body Weight and Level of Fatness Among Children" by Ross E. Andersen et al (1998)[1]

What is the background to this research[edit]


In the past two decades the prevalence of childhood obesity has risen greatly worldwide.[2] The Definition of obesity is an excessive amount of adipose tissue which can lead to serious health complications.[3] Obesity is measured through BMI (Body Mass Index) and is classified as a BMI over 30, in children this is then compared to a chart that adjusts BMI for age.[3][4] The prevalence of childhood obesity has reached epidemic levels in many developed countries, including the United States in which this study was conducted, with 25% of children classified as overweight and 11% obese.[5] Childhood obesity is also a significant indicator of adult obesity and its associated co-morbidities with body mass index at age 9 demonstrating a strong correlation with body mass index at age 50.[6] The rise in severe level obesity and obesity in general has been attributed to a combination of factors including; genes, dietary intake and physical activity.[7] Obesity in the simplest sense is caused by an energy imbalance, being an excess of energy consumed to energy expended.[1][2]This particular study aims to assess the effect of increased time spent watching television in children and its relationship with rising levels of obesity.[1]

Comorbidities of childhood obesity[edit]

There are a variety of comorbidities associated with childhood obesity, some of these include but are not limited too;

  • Cardiovascular
    • Dislipidemia
    • Hypertension
    • Chronic Inflammation
  • Psychological
    • Depression
    • Anxiety
    • Eating Disorders
  • Endocrine
    • Type 2 Diabetes
    • Insulin Resistance
    • Glucose intolerance
    • Precocious Puberty
  • Gastrointenstinal
    • Hepatic Steatosis (Fatty liver disease)
    • Cholelithasis (gallstones)
  • Respiratory
    • Asthma
    • Sleep Apnea


Where is the research from?[edit]

The research was conducted between 1988 and 1994 with 4063 children surveyed between the ages of 8-16 years old as part of the United States National Health and Nutrition Examination Survey (NHANES).[1]The article was published in JAMA, The Journal of the American Medical Association which is a peer reviewed Journal published 48 times per year.[9]

What kind of research was this?[edit]

This study was a nationally representative cross sectional study involving both an in person interview and medical examination.[1] Cross Sectional studies involve the capturing and measurement of specific variables to gain insights into objectives of particular interest within a specific population group.[10] Cross sectional studies give insights into specific outcomes and characteristics over the time period the study is conducted and are commonly used for public health planning.[10]

What did the research involve?[edit]

The study involved the assessment of a variety of outcomes. The main outcomes measured included; episodes of vigorous activity, daily hours of television watched, as well as their relationship to BMI (body mass index) and adiposity.[1] These outcomes were found through the use of survey's. The survey was conducted in an interview format in the children's home and then a detailed examination was performed in a mobile examination center calculating body measurements.[1]


Due to the nature of the population interviewed (children) answers given may not be as accurate as those given by adults. Results may be over or under estimated as children interviewed may be trying to give the interviewer what they perceive as the 'correct' answer.In addition to this some of the questions asked such as "how many times a week had they played or exercised enough to make them sweat or breathe hard."[1] rely on the child's subjective perception of difficulty. More accurate measures could be obtained through more invasive studies such as the use of accelerometers however it would be both expensive and difficult to obtain the ethics for such a study given the population group. The study also states it oversampled Mexican Americans, non-Hispanic blacks and younger people to gain a more reliable estimate of these specific populations however this may skew results when trying to gain a picture of the whole population. Another limitation of this study is the age of this study, more contemporary research is needed to examine the current state of this issue.

What were the basic results?[edit]

Overall 80% of children interviewed reported playing or exercising "that made them sweat or breathe hard" 3 or more times per week.[1] The rate was slightly higher for boys at 85% than in girls at 74%.[1] Interestingly this gap seemed to widen with increasing age with boys and girls demonstrating similar levels of activity through the ages 8-10 with girls levels dropping significantly in the 14-16 year age bracket to 65% (3 or more sessions).[1] When examining BMI and trunk skinfolds in relation to physical activity an interesting statistic was the boys who reported 6 to 8 sessions of vigorous activity were found to have the highest BMI's.[1] This could be considered evidence of flaws in the gathering of this data as such a finding is contradictory to other literature.[2][3][5][6][7] When examining the relationship between hours of television watched and BMI and skinfold thickness results are closer to what would be expected. Boys and girls who watched 4 or more hours of television a day were found to have the highest skinfold thickness and BMI in contrast to those who only watched 1 hour of television a day having the lowest skinfold thickness and BMI.

What conclusions can we take from this research?[edit]

Whilst results surrounding the relationship between physical activity levels and BMI and skinfold thickness were inconclusive with the relationship varying, the relationship between increased tv viewing time and higher BMI and skinfold thickness is undeniable.[1] The root cause of the issue is the increasing consumption of calorie dense foods and rising levels of sedentary behaviour (watching tv).[1][2][6][7] One of the main influences on environmental factors for children are their parents, the parents are the ones purchasing food for their children so if they aren't educated on proper nutrition this issue will continue to become more prominent. When identifying the various factors linked to childhood obesity parents are the most significant factor in this current epidemic.[5][6][11]

Practical advice[edit]

The root cause of this issue is an energy imbalance, Children are consuming too many energy dense foods whilst spending too much time sedentary (watching TV). Methods to combat this epidemic could include school based interventions, such as encouraging outdoor play time and increasing the number of healthy food options in canteens.[12] With parental influence being a significant factor, parental education on healthy eating habits and the importance of encouraging physical activity and reducing screen time will assist in reducing the prevalence of this issue.

Further Information and Resources[edit]


  1. Andersen RE, Crespo CJ, Bartlett SJ, Cheskin LJ, Pratt M. Relationship of physical activity and television watching with body weight and level of fatness among children: results from the Third National Health and Nutrition Examination Survey. Jama. 1998 Mar 25;279(12):938-42.
  2. De Onis M, Blössner M, Borghi E. Global prevalence and trends of overweight and obesity among preschool children–. The American journal of clinical nutrition. 2010 Sep 22;92(5):1257-64.
  3. What is Obesity? - Obesity Action Coalition [Internet]. Obesity Action Coalition. 2018 [cited 14 September 2018]. Available from: https://www.obesityaction.org/get-educated/understanding-your-weight-and-health/what-is-obesity/
  4. Gavin M. Body Mass Index (BMI) Charts [Internet]. Kidshealth.org. 2015 [cited 14 September 2018]. Available from: https://kidshealth.org/en/parents/bmi-charts.html
  5. Dehghan M, Akhtar-Danesh N, Merchant AT. Childhood obesity, prevalence and prevention. Nutrition journal. 2005 Dec;4(1):24.
  6. Wright CM, Parker L, Lamont D, Craft AW. Implications of childhood obesity for adult health: findings from thousand families cohort study. Bmj. 2001 Dec 1;323(7324):1280-4.
  7. Biro FM, Wien M. Childhood obesity and adult morbidities–. The American journal of clinical nutrition. 2010 Mar 24;91(5):1499S-505S.
  8. Sahoo K, Sahoo B, Choudhury AK, Sofi NY, Kumar R, Bhadoria AS. Childhood obesity: causes and consequences. Journal of family medicine and primary care. 2015 Apr;4(2):187.
  9. Jamanetwork.com. (2018). JAMA – The Latest Medical Research, Reviews, and Guidelines. [online] Available at: https://jamanetwork.com/journals/jama [Accessed 14 Sep. 2018].
  10. Levin KA. Study design III: Cross-sectional studies. Evidence-based dentistry. 2006 Mar;7(1):24.
  11. Ebbeling, C., Pawlak, D. and Ludwig, D. (2002). Childhood obesity: public-health crisis, common sense cure. The Lancet, [online] 360(9331), pp.473-482. Available at: http://corcom130-sp10-advertising.wikispaces.umb.edu/file/view/Childhood%20obesity.pdf/132419279/Childhood%20obesity.pdf.
  12. Karnik S, Kanekar A. Childhood obesity: a global public health crisis. Int J Prev Med. 2012 Jan 1;3(1):1-7.