The Journal of Pediatrics
Volume 149, Issue 1 , Pages 5-6, July 2006

Evidence-based medicine and the obesogenic environment

  • Reginald L. Washington, MD

      Affiliations

    • Corresponding Author InformationReprint requests: Reginald L. Washington, MD, Medical Director, Rocky Mountain Pediatric Cardiology, Pediatrix Medical Group, 1601 E. 19th Avenue, Suite 5200, Denver, CO 80218.

Medical Director, Rocky Mountain Pediatric Cardiology, Pediatrix Medical Group, Denver, CO

Article Outline

 

The large increase in overweight children over the last 2 decades has been well documented; 15% of children age 6 to 19 years are now overweight, 3 times the number recorded in 1980. Childhood obesity has been identified in all socioeconomic groups and in all industrially developed countries.1 This increased incidence of obesity in children (as well as adults) has occurred over a very short period, suggesting that it is not the result of a massive genetic shift.

See related articles, p 32 and p 38

Obesity is due mainly to poor lifestyle behaviors, such as the consumption of fats and sugared products, which are commonly combined with an environment characterized by a marked reduction in physical activity. In short, there is an increase in energy intake and a decrease in energy expenditure in our youth.

A risk factor is a factor that causes a person or a group of people to be particularly susceptible to an unwanted, unpleasant, or unhealthy event, such as obesity. Multiple risk factors have been implicated in this obesity epidemic. These risk factors may be categorized into 3 groups. First, a partial list of risk factors for increased energy intake includes increased consumption of fast foods, sweetened drinks, large portion sizes, and calorie-dense foods, accompanied by decreased consumption of fruits and vegetables. Second, risk factors that lead to decreased energy expenditure include excessive screen time (television, computer, and video games), decreased physical education in school and sports activities for non-athletes, and excessive homework. Third, and finally, there are also unalterable risk factors involving a child’s genetic makeup. All of these risk factors interact with one another and are most useful if they can be easily identified, if they can be modified, and if through this modification the incidence of the unwanted, unpleasant, or unhealthy events, such as obesity, can be decreased.

Evidence-based medicine and the identification of “best practices” are now the cornerstones of clinical practice. This philosophy, however, is not as straightforward when dealing with the obesity epidemic, which is in a sense a “perfect storm.” Obesity is the result of many risk factors, some of which can be modified and others that cannot. Adding to the complexity of the “perfect storm” is the fact that these risk factors relate to one another, making the study of individual risk factors difficult; for example, children who watch an excessive amount of television will likely snack on high-calorie foods (eg, chips and soda) while doing so. In addition, by definition, children who are sedentary (ie, watching television or playing computer games most of their leisure time) are not being physically active and likely will not enjoy sports as they mature. Studies have demonstrated that family units often watch television together, are sedentary together, and share unhealthy eating habits.2, 3, 4 Consequently, satisfying the requirements of evidence-based medicine is difficult if this requires the isolation and study of individual risk factors, because it is impossible to control the other risk factors. Thus, it stands to reason that common sense is needed when evaluating data from studies that evaluate isolated risk factors.

Two articles in this issue of The Journal add to the evidence indicating that these risk factors are important to the development of childhood obesity. Both studies use state-of-the-art techniques to measure whole body composition and calculate total body fat mass. In the study by Davison et al,5 data were collected on 7-, 9-, and 11-year-old girls regarding the amount of television watched, percentage of body fat, and body mass index. Children who entered the study with a normal weight but exceeded the American Academy of Pediatrics’ recommendations for television watching (2 hours or less daily6) were 5 times more likely to be overweight when evaluated at the conclusion of the study. This finding strongly suggests that excessive television watching in this age group is a contributor to future obesity.

The study by Dencker et al7 measured total body fat mass and physical activity (using accelerometers) in third- and fourth-grade children. The children in the lower 2 quartiles in activity had a 3 to 4 times greater risk of being overweight. In addition, this study suggests that physical activity is most effective when it is vigorous. The current Centers for Disease Control recommendation is that children engage in 60 minutes or more of physical activity daily.8 Sedentary activities, such as excessive television viewing, computer use, and video games, should be discouraged. The Centers for Disease Control also recommends daily quality physical education from kindergarten through grade 12 to combat sedentary behavior.

The obesity epidemic is growing. It is imperative that risk factors be explored and understood. It is especially important to understand how these risk factors interact with one another. This knowledge will increase the evidence base and aid in the development of sound measures to use in dissipating the “perfect storm” that has given rise to increased obesity worldwide.

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References 

  1. Parizkova J , Hills A . Childhood obesity (Prevention and treatment) . 2nd ed. Boca Raton, FL: CRC Press; 2005;
  2. Fisher JO , Mitchell DC , Smiciklas-Wright H , Burch LL . Parental influences on young girls’ fruit and vegetable micronutrient and fat intakes . J Am Diet Assoc . 2002;102:58–64
  3. Cutting TM , Fisher JO , Grimm-Thomas K , Birch LL . Like mother, like daughter (familial patterns of overweight are mediated by mother’s dietary disinhibition) . Am J Clin Nutr . 1999;69:608–613
  4. Davison K , Francis L , Birch L . Links between parents’ and girls’ television viewing behaviors (a longitudinal examination) . J Pediatr . 2005;147:436–442
  5. Davison KK , Marshall SJ , Birch LL . Cross-sectional and longitudinal associations between TV viewing and girls’ body mass index, overweight status, and percentage body fat . J Pediatr . 2006;149:32–37
  6. American Academy of Pediatrics . Policy statement (children, adolescents, and television) . J Pediatr . 2001;107:423–426
  7. Dencker M, Thorsson O, Karlsson MK, Linden C, Eiberg S, Wollmer P, et al. Daily physical activity related to body fat in children aged 8 to 11 years . J Pediatr . 2006;149:38–42
  8. Strong WB , Malina RM , Blimkie CJR , Daniels SR , Dishman RK , Gutin B , et al.   Evidence-based physical activity for school-aged youth . J Pediatr . 2005;146:732–737

PII: S0022-3476(06)00210-1

doi:10.1016/j.jpeds.2006.03.038

Refers to article:

  • Cross-sectional and longitudinal associations between TV viewing and girls’ body mass index, overweight status, and percentage of body fat

    Kirsten Krahnstoever Davison, Simon J. Marshall, Leann L. Birch
    The Journal of Pediatrics July 2006 (Vol. 149, Issue 1, Pages 32-37)

  • Daily physical activity related to body fat in children aged 8-11 years

    M. Dencker, O. Thorsson, M.K. Karlsson, C. Lindén, S. Eiberg, P. Wollmer, L.B. Andersen
    The Journal of Pediatrics July 2006 (Vol. 149, Issue 1, Pages 38-42)

The Journal of Pediatrics
Volume 149, Issue 1 , Pages 5-6, July 2006

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