Evidence Digest

The Latest Evidence to Guide ObesityPrevention, Policy, and Clinical Practicewith Overweight Children and Adolescents

Bernadette Mazurek Melnyk, RN, PhD, CPNP/NPP, FAAN, FNAP

The purpose of Evidence Digest, a recurring columnin Worldviews on Evidence-Based Nursing, is to pro-

vide concise summaries of well-designed and/or clini-cally important recent studies along with implications forpractice, research, administration, and/or health policy.Articles highlighted in this column may include quanti-tative and qualitative studies, systematic and integrativereviews, outcomes evaluation studies, as well as consensusstatements by expert panels. Along with relevant impli-cations, the level of evidence generated by the studies orreports highlighted in this column (see Figure 1) is in-cluded at the end of each summary so that readers canintegrate the strength of evidence into their health caredecisions.

• Level I: Evidence from a systematic review or meta-analysis of all relevant randomized controlled trials (RCTs), or evidence-based clinical practice guidelines based on systematic reviews of RCTs

• Level II: Evidence obtained from at least one well-designed RCT • Level III: Evidence obtained from well-designed controlled trials without randomization • Level IV: Evidence from well-designed case-control and cohort studies • Level V: Evidence from systematic reviews of descriptive and qualitative

studies • Level VI: Evidence from a single descriptive or qualitative study • Level VII: Evidence from the opinion of authorities and/or reports of expert committees

Modified from Guyatt & Rennie, 2002; Harris et al., 2001

Figure 1. Rating system for the hierarchy of evidence (fromMelnyk & Fineout-Overholt 2005).

AN EVIDENCE REVIEW OF SCHOOL-BASEDOBESITY PREVENTION PROGRAMS

Kropski J.A., Keckley P.H. & Jensen G.L. (2008). School-based obesity prevention programs: An evidence-based re-view. Obesity, 16(3), 1009–1018.

Copyright ©2009 Sigma Theta Tau International1545-102X1/09

Purpose: The purpose of this review was to examinethe effectiveness of school-based programs for reducingoverweight or obesity in children.

Design: Systematic review.Methods: The authors reviewed experimental and quasi-

experimental studies published from January 1, 1990,through December 2005 throughout the globe that testedschool-based curricular or environmental preventive inter-ventions. Databases searched included PubMed, biologicalabstracts, and education abstracts. Search terms includedschool, obesity, overweight, weight, prevention, nutrition,physical activity, trial, body mass index (BMI), bloodpressure, cholesterol, environment, child, adolescent, foodchoices, metabolic syndrome, and combinations of theseterms. Identification of other studies occurred through re-viewing references of the studies that were yielded throughthe search and personal communication with obesity re-searchers. Inclusion criteria were (1) an experimental orquasi-experimental design, (2) report of primary or sec-ondary outcomes in terms of BMI, (3) report of outcomesat least 6 months after baseline assessment, (4) curricu-lar and/or environmental interventions, and (5) preven-tive interventions involving both overweight and normalweight children. Exclusion criteria included extracurricu-lar delivery of the intervention, the targeting of overweightchildren specifically, and measurement of outcomes at lessthan 6 months following baseline assessment. The reviewfollowed guidelines by the grade working group, whichrates the design, methodological strengths and weaknesses,and significance of the findings to characterize the qualityof evidence from the study. Each study was graded in-dependently by two reviewers on 15 criteria (e.g., meansof randomization, study power, adjustment for baselinecovariates, and attrition). Inconsistencies were settled byconsensus discussion by the authors.

Results: Fourteen studies were identified, including (1)one that involved a nutrition only intervention, (2) twophysical activity promotion interventions, and (3) 11 stud-ies that combined nutrition education and physical ac-tivity. Ten of the studies generated grade 2 evidence,which the authors classified as low-quality evidence from

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observational studies. Only one study generated grade 4evidence, which was classified as high-quality evidencegenerated from a clinical trial. In that randomized clinicaltrial, the odds ratio for overweight was reduced in girlsonly, while four grade 2 studies reported significant im-provement in body mass index (BMI) or at-risk-for over-weight or overweight prevalence in boys, girls, or both.Twelve of the studies reviewed reported significant im-provement in at least one measure of dietary intake, physi-cal activity, and/or sedentary behavior. Additionally, mostof the studies targeted 7- to 10-year-old children. The in-vestigators found the overall quality of the evidence to beweak and therefore specific conclusions about the effec-tiveness of interventions on weight outcomes could notbe made. Thirteen of the 14 studies were underpowered,and therefore Type II error was quite likely. Pooling of thedata to conduct a meta-analysis was not possible due toinconsistencies in reporting of specific outcome measures.The authors concluded that there may be gender differ-ences in how children respond to certain interventions.They also noted that interventions specifically involvingthe families of children have not been more effective inprimary or secondary prevention settings than those with-out specific targeting or inclusion of parents or families.However, the ability to draw strong conclusions about theefficacy of school-based obesity prevention programs waslimited by the small number of published studies as wellas methodological weaknesses of those studies included inthe review.

Commentary with Implications for Action in EducationalSettings and Future Research. This systematic reviewwas rigorously conducted. However, due to the paucityof randomized controlled trials testing preventive in-terventions in school settings and serious methodolog-ical flaws in the majority of school-based interventionstudies reviewed, it was difficult to draw firm conclu-sions regarding the most efficacious interventions thatshould be implemented in school settings to reduceoverweight or obesity in children and teens. Some ofthe lower quality studies in this systematic review in-dicated that a combination of nutrition and physicalactivity seemed to have the best outcomes. This reviewpoints to an urgent need for randomized controlled tri-als in school settings that use similar outcome measuresin order to build a strong evidence base to guide futureeducational programming regarding the prevention ofchild and adolescent overweight and obesity. As mostof the studies targeted 7- to 10-year-old children, thereis a tremendous need to target adolescents with devel-opmentally appropriate interventions as this is the stage

when parents are becoming less of an influence as peerstake on a more influential role, and healthy lifestylebehaviors are being formulated. There is also a press-ing need for preventive interventions targeting youngchildren less than 7 years of age.

Level of Evidence: I

A POLICY-BASED SCHOOL PROGRAMREDUCES THE INCIDENCE OFOVERWEIGHT IN CHILDREN

Foster G.D., Sherman S., Borradaile K.E., Grundy K.M.,Vander Veer S.S., Nachmani J., Karpyn A., Kumanyika S.& Shultz J. (2008). A policy-based school interventionto prevent overweight and obesity. Pediatrics, 121, e794–e802.

Purpose: The purpose of this study was to evaluate theeffects of a multicomponent school nutrition policy initia-tive on the prevention of overweight and obesity amongchildren in fourth through sixth grades over a 2-yearperiod.

Design: Randomized controlled trial.Sample/Setting: A total of 1,349 students in grades

four to six from 10 schools in a United States city inthe mid-Atlantic region participated in the study, withmore than 50% eligible for free or reduced priced meals.More than 40% of the sample was overweight or obese(>85%) and 23.8% were obese (>95%). Black childrencomprised nearly half the sample and there were moreHispanic children in the intervention group.

Methods: Ten schools were selected from 27 kinder-garten through eighth grade schools in which more than50% of the students were eligible for free or reducedpriced meals. The 27 schools were first divided into fiveclusters of 4–7 schools each, based on school size andtype of food service (e.g., full service or heat and serve).Schools within each cluster were then invited to partic-ipate in the study. When two schools from each clusteragreed to participate, each school was randomly assignedto either the experimental intervention or the controlcondition. The schools were the unit of analysis. Afterwritten parental consent and child assent were obtained,baseline assessments were gathered on the students, in-cluding weight and height. Dietary intake was measuredwith the youth/adolescent questionnaire. Physical activ-ity and sedentary behavior, including television viewing,was measured with the youth/adolescent activity ques-tionnaire. In addition, body image was measured usingthe body dissatisfaction subscale of the eating disorderinventory.

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The experimental intervention was developed and de-livered by the Food Trust, which is a community-basedorganization funded by the U.S. Department of AgricultureFood Stamp Nutrition Education Program. A task force wasformed that determined how best to adapt and implementthe Centers for Disease Control and Prevention Guidelinesto Promote Lifelong Healthy Eating and Physical Activity.Committees were formed to make recommendations onthe CDC guidelines and to work with the food servicesdivision to remove from the intervention schools all so-das, sweetened drinks, and snacks that did not meet thestandards set by the committee. The experimental inter-vention also included a school self-assessment that usedthe CDC school health index, nutrition education, nutri-tion policy, social marketing, and parent outreach. Afterconducting the assessment, schools developed an actionplan for change (e.g., limiting use of food as a reward,promoting active recess, and serving breakfast in the class-rooms). All staff members in the intervention schools wereoffered 10 hours of training in nutrition education peryear, and the goal was to provide students with 50 hoursof food and nutrition education per school year. All foodssold and served to students in each of the interventionschools were based on the Dietary Guidelines for Ameri-cans (e.g., beverages limited to 6 oz servings of 100% juiceand low-fat milk). Social marketing included raffles thatrewarded healthy eating with prizes, such as bicycles andjump ropes. Lastly, nutrition educators worked with fam-ilies on healthy eating. One school chose to have a weeklybreakfast club with athletes from a local university.

Findings: Due to baseline differences between the exper-imental and control students in race/ethnicity, that variablewas controlled for in the statistical analyses along withgender and age. Schools in which the multicomponent in-tervention was implemented evidenced a 50% reduction inthe incidence of overweight in comparison to the controlschools. Specifically, only 7.5% of children in the exper-imental intervention schools became overweight in com-parison to 14.9% in the control schools after 2 years. Theprevalence of overweight was also lower in the interven-tion schools and that prevalence decreased by 10.3% inintervention schools compared to a 25.9% increase in con-trol schools. The intervention was more effective in reduc-ing the prevalence of overweight among black children.The odds of incidence of overweight were approximately33% lower for the intervention group than for the con-trol group. There were no differences in the prevalenceof obesity (>95 BMI percentile) or in the remission ofoverweight or obesity (i.e., students who were overweightor obese at baseline but not at follow-up) at the 2-yearfollow-up. There were also no differences in self-reportedconsumption of fruits and vegetables and physical activity

between the two groups, but there was a decrease in seden-tary behavior in the intervention group. There were noadverse effects of the intervention as there were no bodyimage differences between the experimental and controlstudents. No schools dropped from the study, but individ-ual attrition rate was 36% at 2 years for the interventionstudents versus 39.2% for the controls. The major reasonfor attrition was transfers.

Commentary with Implications for Action in EducationalSettings, Policy, and Future Research. One of the keystrengths of this study was that it was a randomizedcontrolled trial, which is the strongest design for test-ing cause-and-effect relationships. It also allowed inter-vention schools to individualize their multicomponentinterventions to what might work best at their insti-tutions, although the individualization of the interven-tions makes it difficult for other schools to replicateand expect the same results as well as to understandexactly which components of the intervention resultedin the successful outcomes. From the findings, it couldbe assumed that it was nutrition policy/environmentalchanges made in the schools that may have had themost potent positive effects on the outcomes along witha decrease in sedentary behavior in the experimentalgroup students. Analyses did not include assessing pro-cess variables to further understand the mechanismsthrough which the intervention led to a positive impacton outcomes, which is a weakness of the majority ofobesity prevention and treatment studies. Understand-ing the process through which interventions work isnecessary to extend the science in the area. Use of onlyself-report measures for food consumption and activitywas also a limitation in this study.

Despite the positive effects of the experimental in-tervention on child outcomes in this study, the inci-dence of overweight in the experimental schools was7.5% over the 2-year period. This indicates that evenmore aggressive intervention efforts must be institutedto curtail the number of middle school students whodevelop overweight and obesity. Schools are an out-standing venue to develop and test interventions to ad-dress the overweight epidemic. Healthy nutrition andphysical education mandates/policies can be institutedin schools to impact large numbers of children. If chil-dren do not have access to sugared beverages, nonnutri-tious meals and unhealthy snacks, they will not be ableto eat them. Daily physical educational requirementsin schools could also increase the energy expended toreduce the odds of developing overweight. Along with

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environmental controls/policies, it is imperative to de-velop and test interventions that will assist children andteens in engaging in healthy habits that they will sustainover a lifetime.

Level of Evidence: II

OVERWEIGHT IN ADOLESCENTS LEADSTO FUTURE CORONARY HEART DISEASE

Bibbins-Domingo K., Coxson P., Pletcher M.J., LightwoodJ. & Goldman L. (2007). Adolescent overweight and fu-ture adult coronary heart disease. New England Journal ofMedicine, 357(23), 2371–2379.

Purpose: The purpose of this study was to determinethe effect of being overweight in adolescence on coronaryheart disease (CHD) in adulthood.

Design: Prevalence study.Sample: Subjects used in this study were from the

National Health and Nutrition Examination Surveys(NHANES).

Methods: The prevalence of obese 35-year-olds in 2020was estimated on the basis of adolescent overweight in2000. Using the CHD policy model, a state transition com-puter simulation of U.S. residents 35 years of age or olderwas then used to project the annual excess incidence andprevalence of CHD, the total number of excess CHD events,and excess deaths from CHD and other causes attributableto obesity from 2020 to 2035. Adolescent overweight wasdefined as a weight above the 95 percentile on the Centersfor Disease Control and Prevention. Adult obesity was de-fined as a BMI of 30 or more. Data used for the modelingtechniques were from NHANES I (1971–1974), NHANESII (1976–1980), NHANES III (1988–1994), and NHANESIV (1999–2000) to determine the proportion of teens be-tween the ages of 12 and 19 years who were above the 95percentile and the proportion of obese 35-year-old menand women. Data from the Framingham Heart Study werealso analyzed. The investigators modeled successive co-horts of 35-year-olds from 2020 to 2035 to calculate theestimated effect on CHD events (e.g., first myocardial in-farction, cardiac arrest, and death from CHD).

Findings: The prevalence of adolescent overweight in2000 was 16.7% in boys and 15.4% in girls. Overweightin adolescence is projected to increase the prevalence ofobesity in 35-year-olds in 2020 with a range of 30–37% inmen and 34–44% in women.

An increase in the number of CHD events and deaths isprojected to occur in young adulthood as a result of the in-crease in obesity. It is estimated that the prevalence of CHDwill increase by a range of 5–16%, with more than 100,000

excess cases of CHD attributable to the increase in obesity.The number of excess deaths from CHD is projected to risefrom 59 in 2020 to 3,600 in 2035. Deaths associated withobesity but not CHD are projected to increase by 4% eachyear.

Commentary with Implications for Action in ClinicalPractice, Policy, and Future Research. Although cau-tion must always be used in interpreting projectionsinto the future as changes in treatment can occur alongwith factors influencing the outcome, the findings fromthis study are very alarming. The findings indicate thatadolescent overweight is likely to continue to have asubstantial adverse impact on adult health well into thefuture. Since childhood and adolescence are the foun-dation for adult health, more resources must be de-voted to preventing and treating child and adolescentobesity. Clinicians must deliver evidence-based devel-opmentally sensitive interventions to enhance healthyeating and activity patterns in children and teens alongwith their families. Policy makers need to introducestate and federal regulations to institute practices (e.g.,required daily physical education in schools and no un-healthy snacks in vending machines) and fund promis-ing research that will curtail the epidemic.

Level of Evidence: VI

ADOLESCENT OBESITY INCREASESTHE RISK FOR MAJOR DEPRESSIVE

AND ANXIETY DISORDERS

Anderson S.E., Cohen P., Naumova E.N., Jacques P. &Must A. (2007). Adolescent obesity and risk for subsequentmajor depressive disorder and anxiety disorder: Prospec-tive evidence. Psychosomatic Medicine, 69, 740–747.

Purpose: The purpose of this study was to determinewhether adolescent obesity is associated with the risk fordevelopment of major depressive disorder or anxiety dis-order.

Design: Prospective community-based cohort study.Sample/Setting: The cohort was composed of a 1975

sample of 976 families with a 1- to 10-year-old childwho resided in upstate New York, USA. The sample wasrepresentative of the region’s demographic characteristicsat the time and was composed of 91% white and 8% blackindividuals. It was composed of 820 participants who wereassessed at four times between 1983, when they were 9 to18 years of age, and 2003, when they were 28 to 39 years ofage. The final sample included 701 individuals, including

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351 females and 350 males, who were not missing adoles-cent weight status and who were assessed at least one ormore times during the follow-up.

Methods: The participants were assessed at each of thefollowing waves: (1) wave 1 (the number of subjects =776), (2) wave 2 (number of subjects = 775), (3) wave 3(number of subjects = 776), and (4) wave 4 (number ofsubjects = 661). Subject retention was 80% at wave 4. In-home interviews at each wave were conducted by trainedinterviewers. Written informed consent was obtained andthe study was approved by the appropriate institutional re-view boards. Major depressive disorder (MDD) and anxietydisorders were assessed at each wave using the diagnosticinterview schedule for children (DISC) with both mothersand children at waves 1 and 2. At wave 3, the DISC wasadministered to participants with minor adjustments forage. At wave 4, disorders were assessed with the structuredclinical interview for DSM-IV (SCID-IV) disorders. Weightand height of the children were reported by the mother atwave 1 and then by the participants at the subsequentwaves. Adolescent obesity was defined as a BMI z-score >

95 percentile and overweight as a BMI > 85 percentile.Socioeconomic status and parental psychopathology wereused as covariates.

Findings: Obesity in adolescent females predicted an in-creased risk for major depressive and anxiety disorders inadulthood, nearly four times the risk for nonoverweightfemales. Obesity in males was not associated with an in-creased risk for MDD or anxiety disorders in adulthood.

Commentary with Implications for Action in ClinicalPractice and Future Research. A major strength of thisstudy is that it was designed as a prospective study of a

cohort over 20 years and did not use a cross-sectionaldesign. There have been extensive debate and conflict-ing findings in the literature regarding whether obe-sity causes depression and whether depression causesobesity. This study provides supporting evidence thatobesity may very well be a major influencing factor inthe development of depressive and anxiety disorders.Therefore, interventions with overweight/obese chil-dren and teens should contain a strong mental healthcomponent (e.g., cognitive-behavioral skills building)along with nutrition education and physical activity.More randomized clinical trials are needed to deter-mine whether adding a salient mental health compo-nent to decrease depressive and anxiety symptoms inoverweight children and teens can have value-addedbenefits in the prevention of these disorders and sus-tainable healthy behaviors.

Level of Evidence: VI

ReferencesGuyatt G. & Rennie D. (2002). Users’ guides to the medical

literature. Washington, D.C.: American Medical Asso-ciation Press.

Harris R.P., Hefland M., Woolf S.H., Lohr K.N., MulrowC.D., Teutsch S.M. & Atkins D. (2001). Current meth-ods of the U.S. Preventive Services Task Force: A reviewof the process. American Journal of Preventive Medicine,20(3 Suppl.), 21–35.

Melnyk B.M. & Fineout-Overholt E. (2005). Evidence-based practice in nursing and healthcare. A guide tobest practice. Philadelphia: Lippincott, Williams &Wilkins.

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