obesity | VOLUME 16 NUMBER 5 | MAY 2008 1009
nature publishing group
behavior and psychology
School-based Obesity Prevention Programs:
An Evidence-based Review
Jonathan A. Kropski1, Paul H. Keckley1 and Gordon L. Jensen2
objective: This review seeks to examine the effectiveness of school-based programs for reducing childhood
overweight or obesity.
Methods and Procedures: A systematic review of the research literature published since 1990 was conducted to
identify experimental or quasi-experimental school-based curricular or environmental preventive interventions, with
evaluation ≥6 months after baseline, which reported outcomes in terms of a measure of overweight.
Results: Fourteen studies were identified, including one involving a nutrition-only program, two physical activity
promotion interventions and eleven studies combining nutrition and physical activity components. Most studies
(n = 10) offered weak (grade 2) quality evidence. One study offered strong (grade 4) evidence reducing the odds
ratio for overweight in girls only, while four grade 2 studies reported significant improvements in BMI or at-risk-for
overweight or overweight prevalence in boys, girls, or both. Twelve studies reported significant improvement in at least
one measure of dietary intake, physical activity, and/or sedentary behavior.
Discussion: Our ability to draw strong conclusions as to the efficacy of school-based obesity prevention programs
is limited by the small number of published studies and by methodological concerns. Qualitative analysis suggests
programs grounded in social learning may be more appropriate for girls, while structural and environmental
interventions enabling physical activity may be more effective for boys. High-quality evaluation protocols should be
considered essential components of future programs.
Obesity (2008) 16, 1009–1018. doi:10.1038/oby.2008.29
Data from the 2003–2004 NHANES survey indicated 17.1%
(95% confidence interval = 14.7–19.5) of US children were
overweight while 33.6% (95% confidence interval = 30.1–37.1)
were considered at-risk for overweight. Significant increases
in the prevalence of at-risk-for overweight and overweight
among children and adolescents aged 2–19 were reported
from 1999–2000, 2001–2002, and 2003–2004 (1). Childhood
BMI has been shown to correlate with adult BMI, and this rela-
tionship tends to strengthen with increasing child age (2–7).
Increased BMI in youth has been associated with adverse risk
factors for adult disease as well as morbidity and mortality in
adulthood (2,8–14). There is evidence these incremental risks
may be independent of adult BMI (2,15), thus preventing the
development of overweight prior to adulthood may be an effec-
tive means of avoiding these undesirable health outcomes.
the role of schools
In 2005, 42 states introduced legislation designed to pro-
vide nutritional guidance to schools, and these statutes were
enacted in 21 states. Bills offering guidance for physical
education or activity levels in schools were introduced in 44
states and passed in 22. Nineteen states proposed some form
of child BMI reporting to parents, and three states enacted
such programs (16).
A recent nationwide survey found parents cited schools
more frequently than health care providers and the govern-
ment as having “a lot of responsibility” to reduce childhood
obesity. Parents themselves, the media, and individual chil-
dren were also commonly identified (17). Up to 65% of par-
ents feel schools should play a major role in efforts to curb
obesity (18). The vast majority of US children are schooled
outside the home, thus the education system provides an
established infrastructure for targeted implementation of
childhood public health interventions. Schools offer access
to children, the facilities requisite for classroom or physical
education interventions, and the personnel capable of being
involved in such efforts (19).
In light of this recent legislative trend of action and increase
public awareness of childhood and adolescent obesity, there
have been several recently published review articles (19–24)
as well as a set of guidelines (25) addressing school-based
1Vanderbilt Center for Evidence-based Medicine, Nashville, Tennessee, USA; 2Department of Nutritional Sciences, Pennsylvania State University, University Park,
Pennsylvania, USA. Correspondence: Gordon L. Jensen (GLJ1@psu.edu)
Received 15 January 2007; accepted 7 August 2007; published online 28 February 2008. doi:10.1038/oby.2008.29
VOLUME 16 NUMBER 5 | MAY 2008 | www.obesityjournal.org
behavior and psychology
obesity prevention programs within broader discussions
of issues related to obesity. No conclusive evidence of ben-
efit or lack thereof has been demonstrated for school-based
approaches to obesity prevention, and there has been limited
ability to identify intervention components offering more
promising outcomes. This review seeks to provide a focused
evaluation of the quality and results of long-term school-based
obesity prevention programs and to offer guidance for future
investigations into this intervention modality.
Methods and Procedures
To examine the efficacy of school-based programs for improving
weight status in children, a systematic review of the research lit-
erature was conducted. Studies were located through a search of
items published from 1 January 1990 through 31 December 2005
of PubMed, Biological Abstracts, and Education Abstracts. Search
terms included SCHOOL, OBESITY, OVERWEIGHT, WEIGHT,
PREVENTION, NUTRITION, PHYSICAL ACTIVITY, TRIAL, BMI,
BLOOD PRESSURE, CHOLESTEROL, ENVIRONMENT, CHILD,
ADOLESCENT, FOOD CHOICES, METABOLIC SYNDROME,
and combinations thereof. Other studies were sought and identified
through references from previous review articles and primary publica-
tions as well as personal communication with researchers experienced
in the field of obesity. Changing secular trends in overweight and obe-
sity suggested data from the NHANES-3 and -4 periods were most
representative of the current prevalence of overweight in children (26).
To meet the inclusion criteria, studies were required to (i) be experi-
mental or quasi-experimental design, (ii) report primary or secondary
outcomes in terms of BMI, a measure of body fat or obesity/overweight
prevalence, (iii) report outcomes at least 6 months post-baseline,
(iv) be curricular and/or environmental (as opposed to extracurricu-
lar) in design, and (v) apply preventive interventions involving both
overweight and normal-weight children. Frequent causes of exclusion
included extracurricular delivery of the intervention program, specific
targeting of overweight children for inclusion, and inadequate dura-
tion (final evaluation <6 months after baseline).
The principles of evidence-based medicine and use of evidence-based
medicine criteria to analyze the strengths and weaknesses of studies have
been thoroughly discussed elsewhere (27–29). This review adopts the
criteria developed by the GRADE working group (27,30). Briefly, the
design of a study, methodological strengths and weakness, and signifi-
cance of the findings are used to characterize the evidence quality of a
given study. A baseline grade of 1–4 was given to a study according to
its design, and this grade was then adjusted based on features including
confounders, sample size, power, directness, statistical techniques, and
effect size (Table 1). Strong methodology and a large treatment effect
not likely diminished by possible confounders increased the grade of
studies, while concerns related to sources of bias, statistical techniques,
and the validity of findings decreased the grade. Each study was assessed
independently in the context of 15 criteria relating to these issues by two
of the authors; any inconsistencies were settled by consensus discussion
among these authors (Table 2). Specific concerns related to individual
studies are indicated in Table 4. Consensus in assignment of overall grad-
ing score was uniform between the two raters.
Fourteen studies were found to meet the inclusion criteria.
One (31) reported an intervention with only a nutrition com-
ponent. Two trials (32,33) evaluated interventions involving
only physical activity components. The remaining 11 studies
assessed programs with both nutritional and physical activ-
ity components. Study design and intervention characteristics
are summarized in Table 3. One grade 4 study was identified
(Table 4). Three studies offered grade 3 level evidence while
the remaining 10 studies were considered weak evidence.
nutrition vs. control
One small randomized controlled trial (RCT) set in
the United Kingdom evaluated a program designed to
reduce intake of carbonated beverages (31). Compared to
table 1 Grading the evidence
evidenceBase grade Study design
High4 Randomized controlled trial
Moderate3 Quasi-experimental trial
Low2 Observational study
Very low1 All other evidence
Grade modificationStudy characteristics
−1 •Serious design limitation (i.e.,
significant baseline differences,
failure to follow intention to treat
protocol, high level of attrition)
•Some uncertainty of directness
(i.e., questionable validity of
•High probability of reporting bias
•Uncertainty of external validity
−2 •Very serious design limitations
•Serious uncertainty of directness
+1 •Strong association without
consistent, and direct evidence
•All plausible confounders would
have diminished effect size
Reprinted from ref. 30.
table 2 Features assessed for scoring
Means of randomization
Cluster number and size
Differences in baseline covariates
Adjustment for baseline covariates
Blinding of data collectors to intervention status
Validity of measures
Intention to treat protocol
Unit of analysis
VOLUME 16 NUMBER 5 | MAY 2008 | www.obesityjournal.org
behavior and psychology
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