Strategies for the prevention and control of obesity in the school setting: Systematic review and meta-analysis

Article (PDF Available)inInternational journal of obesity (2005) 32(12):1780-9 · January 2009with129 Reads
DOI: 10.1038/ijo.2008.158 · Source: PubMed
Abstract
To determine the effectiveness of school-based strategies for obesity prevention and control using methods of systematic review and meta-analysis. Peer-reviewed studies published between 1966 and October 2004 were considered for review. Studies meeting eligibility criteria were published in English, targeted children aged 3-18 in a school setting, reported weight-related outcomes, included a control measurement and had at least a 6-month follow-up period. Studies employed interventions related to nutrition, physical activity, reduction in television viewing or combinations thereof. Weight related data were analyzed using RevMan software. Sixty-four studies were considered for inclusion. Fourteen did not meet inclusion criteria; 29 were excluded due to poor methodological quality. Twenty-one papers describing 19 studies were included in the systematic review and 8 of these were included in the meta-analysis. Nutrition and physical activity interventions resulted in significant reductions in body weight compared with control ((standardized mean difference, SMD=-0.29, 95% confidence interval (CI)=-0.45 to -0.14), random effects model). Parental or family involvement of nutrition and physical activity interventions also induced weight reduction ((SMD=-0.20, 95%CI=-0.41 to 0.00), random effects model). Combination nutrition and physical activity interventions are effective at achieving weight reduction in school settings. Several promising strategies for addressing obesity in the school setting are suggested, and warrant replication and further testing.

Figures

REVIEW
Strategies for the prevention and control of obesity
in the school setting: systematic review and
meta-analysis
DL Katz
1,2
, M O’Connell
1
, VY Njike
1
, M-C Yeh
1,3
and H Nawaz
4
1
Yale Prevention Research Center, Derby, CT, USA;
2
Department of Epidemiology and Public Health, Yale School of Medicine,
New Haven, CT, USA;
3
Hunter College, School of Health Sciences, Urban Public Health Program, New York, NY, USA and
4
Preventive Medicine Residency Program, Department of Preventive Medicine, Griffin Hospital, Derby, CT, USA
Objective: To determine the effectiveness of school-based strategies for obesity prevention and control using methods of
systematic review and meta-analysis.
Methods: Peer-reviewed studies published between 1966 and October 2004 were considered for review. Studies meeting
eligibility criteria were published in English, targeted children aged 3–18 in a school setting, reported weight-related outcomes,
included a control measurement and had at least a 6-month follow-up period. Studies employed interventions related to
nutrition, physical activity, reduction in television viewing or combinations thereof. Weight related data were analyzed using
RevMan software.
Results: Sixty-four studies were considered for inclusion. Fourteen did not meet inclusion criteria; 29 were excluded due to poor
methodological quality. Twenty-one papers describing 19 studies were included in the systematic review and 8 of these were
included in the meta-analysis. Nutrition and physical activity interventions resulted in significant reductions in body weight
compared with control ((standardized mean difference, SMD ¼0.29, 95% confidence interval (CI) ¼0.45 to 0.14), random
effects model). Parental or family involvement of nutrition and physical activity interventions also induced weight reduction
((SMD ¼0.20, 95%CI ¼0.41 to 0.00), random effects model).
Conclusion: Combination nutrition and physical activity interventions are effective at achieving weight reduction in school
settings. Several promising strategies for addressing obesity in the school setting are suggested, and warrant replication and
further testing.
International Journal of Obesity (2008) 32, 1780–1789; doi:10.1038/ijo.2008.158
Keywords: schools; overweight; systematic review; meta-analysis
Introduction
The prevalence of childhood overweight has tripled over
the past two decades in the United States.
1,2
Applying
the current definition of childhood overweight, the
95th percentile for age- and sex-adjusted body mass index
(BMI), approximately 16% of American children 6–19 years
of age are overweight;
1,2
this conservative definition likely
underestimates the true prevalence of childhood obesity.
The physical health of obese children is compromised in
a manner similar to adults. Childhood obesity is associated
with an increased risk of hyperinsulinemia,
3
insulin-
resistance,
4
type 2 diabetes,
5,6
hypertension,
7,8
hyper-
cholesterolemia,
3
chronic inflammation,
9
abnormalities in
endothelial function,
10
hyperandrogenemia,
4
gallstones,
11
hepatitis,
12,13
asthma, cancer
14
and orthopedic problems.
10
Obesity has also been shown to diminish children’s quality
of life severely
14
and is associated with decreased self-
esteem
15,16
and depressive symptoms.
17
Obese children are
subjected to teasing, discrimination and victimization and
may be socially excluded.
18
In response to these threats, there has been a surge in
obesity research in recent years. Schools have been a popular
setting for implementation of interventions, as they offer
continuous, intensive contact with children during their
formative years. School infrastructure and physical environ-
ment, policies, curricula and personnel have great potential
to positively influence child health. Despite the apparent
advantages of addressing obesity in schools, a relative lack of
Received 30 January 2007; revised 18 August 2008; accepted 18 August 2008
Correspondence: Dr DL Katz, Yale Prevention Research Center, 130 Division
Street, Derby, CT 06418, USA.
E-mail: katzdl@pol.net
International Journal of Obesity (2008) 32, 17801789
&
2008 Macmillan Publishers Limited All rights reserved 0307-0565/08
$
32.00
www.nature.com/ijo
evidence of effectiveness has led some to question the wisdom
of allocating scarce resources to school-based programs. This
issue was the subject of debate among health professionals at
the 2005 annual meeting of the North American Association
for the Study of Obesity in Vancouver, BC.
19
Several systematic reviews of childhood obesity programs
have been published.
20–35
With the exception of one recent
review
20
and an earlier review conducted by our team in
collaboration with the Community Guide Branch of the
Center for Disease Control and Prevention (CDC),
25
this
work is unique in that it focuses specifically on studies
undertaken in schools. Previous reviews have focused solely
on the prevention of obesity
22
or weight loss interventions
among already overweight children.
23
Recognizing that the
strategies to prevent unnecessary weight gain and to treat
obesity in children overlap considerably, this review includes
studies with both aims. Many authors have reported
difficulty in evaluating findings across studies quantitatively.
Although some difficulty was encountered due to hetero-
geneity of outcome measures and specific inter-
vention components, sufficient data were available for
meta-analysis.
Methods
Study identification
The literature search strategy was developed by the research
team and critiqued by an expert panel. The following search
engines were used to locate overweight/obesity intervention
studies published between 1966 and February 2000:
MEDLINE, HealthStar, Psych Info and Embase. Review of
these studies was conducted in collaboration with the CDC
and Prevention’s Guide to Community Preventive Services
branch and has been published.
25
Additional searches were
conducted to retrieve studies published between February
2000 and October 2004 using Medline, Ovid, Cinahl and
PsychInfo. The Cochrane Library was searched to identify
systematic reviews to be used for manual bibliography
searching. Other meta-analyses, review articles and articles
written by prominent authors in the field of obesity were
also reviewed for relevant citations.
To be eligible for inclusion, studies needed to: be published
in English; target children aged 3–18 in a school setting;
report commonly used weight-related outcomes (BMI, body
weight, etc.); include a control measurement (either with
pre/post-measures or using control group(s); and follow
participants for at least 6 months from the beginning of the
intervention. Studies included in the review aimed to
prevent unnecessary weight gain or manage weight, and
employed interventions related to nutrition, physical activity,
reduction in television (TV) viewing or combinations there-
of. The following definitions were used to place studies into
categories on the basis of the mode of intervention:
‘nutrition interventions’ aimed to modify dietary intake of
the students with no explicit focus on physical activity or
TV; ‘physical activity’ (PA) interventions aimed to increase
PA with no focus on dietary intake or TV; ‘TV reduction’
interventions focused only on reducing this sedentary
activity without focus on changing dietary intake or
increasing PA; and ‘combination’ interventions include both
nutrition and PA elements and may also include reduction in
TV viewing.
Data were extracted from each article by two reviewers
independently, using a standardized protocol developed by
the CDC.
36
The CDC’s Community Guide ‘data abstraction
form’ contains two sections eliciting information about
study description and results, followed by a third section to
assess methodological quality. The quality scoring system
takes into account suitability of study design and quantifies
threats to validity.
36
This score is used as the basis for
excluding studies of poor quality from the review. The
two reviewers compared quality scores and data extracted;
the principal investigator was consulted when differing
responses could not be reconciled.
The combined searches identified 64 papers on the basis
of screening of titles and abstracts. Upon review of full text,
14 did not meet inclusion criteria, whereas data abstraction
of the remaining articles resulted in exclusion of 29 with
poor methodological quality, the majority from the initial
review (see flow diagram in Figure 1). Twenty-one papers
were included in the review, describing 19 studies (data from
two studies were published twice, but included in the
analysis once). No studies published before 1980 met
quality criteria. Four of the included studies were published
before 1996, five were published between 1996 and 2000 and
10 were published between 2000 and February 2004.
Of the 19 studies (21 papers) meeting criteria for inclusion,
14 were randomized controlled studies and five were
non-randomized controlled studies. Six of the studies were
‘treatment’, and 13 were strictly primary prevention. These
19 studies intervened with a total of over 13 029 (sample size
not reported in one study) students; 13 took place in
elementary schools, 3 took place in middle schools and 3
targeted high school students. Ten took place in the United
States, whereas nine were conducted overseas. One study
targeted girls only.
All studies incorporated multiple strategies to impact on
the weight status of student populations. Common strategies
included: parent or family member participation;
37–45
changing the physical environment;
43,44,46–48
nutrition/
PA-related classroom instruction;
37–41,43,44,46,49
incorpora-
tion of nutrition/PA/TV reduction lessons across curricula;
50
use of participatory, skill building activities;
37–41,43,44,49
dissemination of educational print materials;
37–40
use of
student competitions;
44
introduction of PA in addition to
PE;
40,41,43
modification to duration, frequency or intensity
of PE activities;
46,49
focus on games, dance or other non-
traditional PA;
51
provision of new PE equipment or funds to
support PE;
52
teacher training;
37–39
and student training in
behavioral techniques such as self-monitoring.
38,39,52,53
Detailed descriptions of each study can be found in Table 1.
Strategies for prevention and control of obesity
DL Katz et al
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International Journal of Obesity
Eight of the 19 studies provided adequate data for
inclusion in the meta-analyses. All the studies included in
the meta-analysis were combination interventions (nutrition
plus physical activity).
37–41,43,44,46,49
Subgroup analyses were
also performed by gender for each intervention type where
applicable.
64 trials identified
50 trials retained
14 trials excluded upon review
of full text
29 trials excluded after data
abstraction due to methodological
21 Potential Trials Retained
19 potential trialsto be includedin
the meta-analysis
8 trials included inthe meta-analysis
8 nutrition plus physical activity
interventions (combination)
2 trials excluded due to report of
data in multiple publications
2 trials excluded because datawere
presented only ingraphs
2 trials excluded due to lack of control
group
1 trial excludedbecause data were
categorical
1 trial excluded because intervention and
control data were already pooled
1 trial excluded due to unknown sample
size
3 studies for 3 different interventions
1 trial lack Standard deviation
21 trials retained
Figure 1 Flow diagram of trial selection.
Strategies for prevention and control of obesity
DL Katz et al
1782
International Journal of Obesity
Table 1 Detailed description of studies included in the review
Author and year study design intervention
type aim of study
Participants/sample size Results
Effect size (CI) Outcome Follow-up
Sallis et al., 1993
Randomized controlled trial
Intervention type: Physical activity (PA)
Study aim: Obesity prevention
Fourth graders from southern California elementary
schools
n ¼ 740
f/u n ¼ 549
NA BMI
Skinfolds
Data are presented in figures only.
2 years
Mo-Suwan et al., 1998
a
Randomized controlled trial
Intervention type: PA
Study aim: prevention of weight gain
Kindergarten students in Thai schools
n ¼ 310 students
f/u n ¼ 294 students
0.09 (0.32 to 0.14) BMI
b
9 months
Sallis et al., 2003
Design: randomized controlled trial
Intervention type: nutrition, PA, environmental and policy
intervention. Parent education component.
Study aim: to increase PA and lower fat intake
Children in grades 6–8 attending one of 24
middle schools in San Diego county, CA.
N ¼ not reported
F/u n ¼ not reported
NA (Self-reported height and weight)
BMI Boys
BMI Girls
24 months
James et al., 2004
a
Design: randomized controlled trial
Intervention type: nutrition
Study aim: prevention of weight gain
School children aged 7–11 in southwest England.
N ¼ 644
F/u n ¼ 574
Girls n ¼ 279
Boys n ¼ 295
0.39 (0.56 to 0.23) BMI
b
Percent of students who are
overweight and obese
12 months
Burke et al., 1998
Randomized controlled trial
Intervention type: nutrition and PA with parent component
Study aim: reduction of cardiovascular disease risk
11-year-old students enrolled in West Australian
school system
n ¼ 18 schools, 800 students
f/u n ¼ 765 students
NA Data are presented in figures only,
but a significant decrease in
skinfold thickness was reported.
1 year
Gortmaker et al., 1999
Randomized controlled trial
Intervention type: nutrition, PA, reducing sedentary time
(TV viewing)
Study aim: to reduce obesity
Multiethnic student population grades 6-8 in
Boston, MA schools
n ¼ 10 schools, 1560 students
f/u n ¼ 1295 students
NA Prevalence of obesity
Absolute difference
Females: 5.5% intervention
vs control
Males: 0.8% intervention vs control
2 years
Nader et al., 1999
a
Randomized controlled trial
Intervention type: nutrition, PA, environment
Study aim: reduction of cardiovascular disease risk
Third to fifth graders in 41 state in the
United States
n ¼ 5106
f/u n ¼ 3692
0.08 (0.15 to 0.01) BMI
b
Skinfold
5 years
Walter et al., 1988
a
and
Walter et al., 1985
Randomized controlled trial
Intervention type: nutrition, PA and parent involvement
Study aim: to reduce cardiovascular disease risk
Fourth graders in selected schools in two NY
counties (Westchester and Bronx)
n ¼ 37 schools
f/u n ¼ 2283 students
0.03 (0.12 to 0.06) Ponderosity index
b
5 years
Tamir et al., 1990
a
Non-randomized controlled trial
Intervention type: nutrition, PA with family component
Study aim: prevention of cardiovascular disease
First-grade students in 16 Jerusalem schools
n ¼ 829
f/u n ¼ 406
0.21 (0.41 to 0.01) BMI
b
2 years
Lionis et al., 1991
a
Non-randomized controlled trial
Intervention type: nutrition, PA with family component
Study aim: prevention of cardiovascular disease
All students in senior year of high school in both
Agios vassilios and Amari provinces in Greece
n ¼ 171
f/u n ¼ 148
0.40 (0.73 to 0.06) BMI
b
1 year
Skybo et al., 2002
a
Non-randomized controlled trial
Intervention type: nutrition, PA with family component
Study Aim: prevention of cardiovascular disease
Third graders in two public schools in the
Midwest, US
N ¼ 58
F/u n ¼ 56
NA Weight (lbs)
b
Percent body fat
1 academic
year
Strategies for prevention and control of obesity
DL Katz et al
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International Journal of Obesity
Table 1 (continued)
Author and year study design intervention
type aim of study
Participants/sample size Results
Effect size (CI) Outcome Follow-up
Grey et al., 2004
a
Randomized controlled trial
Intervention type: nutrition, PA, specialized behavioral
intervention, with family component
Study aim: to slow weight gain
Healthy, English-speaking inner-city students,
New Haven, CT, aged 10–14 with family history
of type 2 diabetes and BMI 495th percentile
N ¼ 41
F/u n ¼ 32
0.55 ( 1.18 to 0.07) BMI
b
Weight (lbs)
Central adiposity
1 year
Caballero et al., 2003 and Lohman et al., 2003.
Randomized controlled trial
Intervention type: nutrition, PA, environmental
intervention and family component
Study aim: to reduce the rate of body fat gain
Schools in 7 American Indian communities across
the United States were eligible if provided meals
onsite, have X15 third grade students, X90%
American Indian, retention of students from third
to fifth grade of X70% over 3 years, physical activity
facilities, approval by community tribe.
N ¼ 1704
F/u n ¼ 1409
NA Weight (kg)
BMI
Percent body fat
3 years
Chen et al., 2001
Design: prospective cohort study
Intervention type: Nutrition and PA
Study aim: lifestyle change and improvement in physiologic
markers, including weight
Overweight adolescent nursing students in
Taiwan
N ¼ 55
F/u n ¼ 49
NA Weight (kg) 12 months
Kain et al., 2004
a
Design: non-randomized controlled trial
Intervention type: nutrition, PA, environmental
intervention and family component
Study aim: prevention of obesity
Chilean children with low SES in grades 4–8
attending one of 5 schools in 3 cities in Chile
(Santiago, Curico, Casablanca). No previous
participation in health promotion program
N ¼ 3577
F/u n ¼ 3086
0.08 ( 0.16 to 0.01) BMI Boys
b
BMI girls
b
BMI z score boys
BMI z score girls
Tricep skinfolds boys
Tricep skinfolds girls
6 months
Neumark-Sztainer et al., 2003
a
Design: randomized controlled trial
Intervention type: nutrition, PA, specialized behavioral
(body-image)
Study aim: prevention of obesity
Adolescent girls attending one of six high schools in
Twin Cities, MN. Self-reported low physical activity,
BMIX75th%, no diagnosis of eating disorder
N ¼ 201
F/u n ¼ 180
1.42 ( 1.75 to 1.09) BMI Girls
b
Number with healthy and unhealthy
weight post intervention/follow-up
8 months
Sahota et al., 2001
Design: randomized controlled trial
Intervention type: nutrition, PA, environment
Study aim: prevention of obesity
School children aged 7–11 attending 1 of 10
primary schools in Leeds, UK
N ¼ 613
F/u n ¼ 595
NA BMI s.d. score
Weight s.d. score
12 months
Warren et al., 2003
RCT
Intervention type: nutrition, PA and family component
Study aim: to prevent obesity
All children in years 1–3 (ages 5–7) in 3
primary schools in Oxford, England
N ¼ 218
F/u n ¼ 181
NA BMI
Percentage overweight
Percentage obese
Weight
Skinfold
WHR
14 months
Robinson, T 1999
a
Randomized controlled trial
Intervention type: behavioral only: reduction of sedentary
behavior (TV, videos)
Study aim: to prevent obesity
Enrollment in grades 3 or 4 in 2 elementary schools
in San Jose, CA
n ¼ 198 students
f/u n ¼ 192 students
0.35 ( 0.63 to 0.06) BMI
b
Skinfold
6 months
Abbreviation: NA, not applicable;
a
Trials included in the meta-analysis.
b
Outcome measures included in meta-analysis.
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DL Katz et al
1784
International Journal of Obesity
Statistical analysis
Data were analyzed using RevMan software version 4.2.
54
For clusters of articles reporting the same outcomes and
shared intervention types (nutrition, PA or combination),
meta-analysis was performed. Data entered in RevMan
included the following: pre/post-changes in outcome mea-
sures for the intervention and the control groups, the
corresponding number of participants for each treatment
group in the trial and standard deviation (s). Where
studies
38,39,51,55,56
reported mean changes in outcome
measures from baseline (pre) to end point (post) for each
intervention group (that is, DIorDC), data were entered in
RevMan with their corresponding number of participants
and ss. For trials
40,41,43,44,46
that reported both pre- and
post-intervention values, changes were computed by sub-
tracting the pre- from the post-measurements. In case of
missing ss, the s’s were estimated by imputing ss of other
studies using the same outcome measures.
57
The standardized mean differences (SMD) were computed
with their 95% confidence interval (CI). We used SMD (that
is, effect size) because the trials included in the analysis
assessed weight loss in different ways (e.g., BMI, weight and
ponderosity). Using SMD transformed the results of trials
into a uniform scale so that they could be pooled. The SMD
gives size of the treatment effect in each trial relative to the
variability observed in that trial. Positive SMD represents
weight gain and a negative SMD represents weight loss.
To assess the net effect of different interventions on weight
loss, we computed pooled SMD and 95% CIs for clusters of
trials with similar interventions. Weight reduction for each
intervention type (nutrition, PA, combination) compared
with placebo was considered statistically significant when
the 95% CI around the pooled SMD did not include zero.
Comparisons across interventions were made also using the
95% CIs around the pooled SMD. When the 95% CIs of
pooled SMD of one intervention was not included within the
95% CI of pooled SMD of another intervention (that is, non-
overlap), we considered the two interventions significantly
different at Po0.05.
The Q test was used to test for heterogeneity.
58
The Q test
is based on the w
2
distribution and provides a measure of the
sum of the squared differences between the results observed
and the results expected in each trial, under the assumption
that each trial estimates the same treatment effect. To obtain
the SMD with 95% CI for treatment and control, we used
a random effects model when heterogeneity (w
2
) was
present (Po0.05); otherwise, the fixed-effects model
was used. The I
2
test was also computed. This statistic
provided the degree of inconsistency of the results of the
trials. The value is expressed as a percentage of the total
variation across trials that are attributed to heterogeneity
rather than chance.
Results
Combination interventions, the single nutrition inter-
vention and TV reduction were equally effective. All
showed significant (Po 0.05) reduction of body weight in
children. The pooled effect sizes of the combination,
nutrition interventions and TV reduction were ((SMD ¼
0.29, 95%CI ¼0.45 to 0.14), random-effects model)
(see Figure 2); (SMD ¼0.39, 95% CI ¼0.56 to 0.23) and
(SMD ¼0.35, 95% CI ¼0.63 to 0.06), respectively. PA
intervention did not show body weight reduction
(SMD ¼ 1.87, 95% CI ¼ 1.31–2.42).
When including only studies with a parent/family com-
ponent in the analysis, the combination intervention
improved body weight in school children ((SMD ¼0.20,
95% CI ¼0.41–0.00), random effects model) (see Figure 3).
The magnitude of the SMD for the combination intervention
decreased ((SMD ¼0.16, 95% CI ¼0.320–0.00), random
effects model) (see Figure 4) when including only studies
with both a family component and an environmental
component.
The TV reduction intervention resulted in significant
reduction in body weight (SMD ¼0.35, 95% CI ¼0.63 to
0.06). This intervention effect (SMD ¼0.35, 95% CI ¼
0.63 to 0.06) did not differ from the effect of nutrition
(SMD ¼0.39, 95% CI ¼0.56 to 0.23), or combination
interventions ((SMD ¼0.29, 95% CI ¼0.45 to 0.14),
random-effects model) (see Figure 2).
In subgroup analysis by gender, the PA study showed
better statistically significant weight reduction in girls
(SMD ¼0.38, 95% CI ¼0.74 to 0.02). The weight
reduction in girls (SMD ¼0.38, 95% CI ¼0.74 to 0.02)
Figure 2 Comparison of nutrition plus physical activity intervention vs control.
Strategies for prevention and control of obesity
DL Katz et al
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International Journal of Obesity
did not differ significantly when compared to boys (SMD ¼
0.14, 95% CI ¼0.17–0.44). In studies employing combi-
nation interventions, girls ((SMD ¼0.53, 95% CI ¼1.37–
0.30), random-effects model) (see Figure 5) showed non-
significant improvement in weight reduction compared with
boys (SMD ¼0.22, 95% CI ¼0.32 to 0.12), fixed-effects
model) (see Figure 6). Girls in the PA intervention (SMD ¼
0.38, 95% CI ¼0.74 to 0.02) showed non-significantly
better improvement compared to girls in trials that used
combination interventions ((SMD ¼0.53, 95% CI ¼1.37–
0.30), random-effects model) (see Figure 5). However, in the
combination interventions, boys ((SMD ¼0.22, 95% CI ¼
0.32 to 0.12), fixed-effects model) (see Figure 6) showed
non-significantly better improvement compared with boys
in the PA intervention trial (SMD ¼ 0.14, 95% CI ¼0.17
to 0.44).
Discussion
This review is an update of the research team’s previous work
published in 2005
25
that concluded that there were not
enough studies of adequate quality available to determine
the effectiveness of school-based interventions, using the
CDC’s Community Guide to Preventive Services criteria.
Although this review update employed Community Guide
Figure 3 Parent or family involvement present: comparison of nutrition plus physical activity intervention vs control.
Figure 4 Family and environmental component present: comparison of nutrition plus physical activity intervention vs control.
Figure 5 Girls only: comparison of nutrition plus physical activity intervention vs control.
Figure 6 Boys only: comparison of nutrition plus physical activity intervention vs control.
Strategies for prevention and control of obesity
DL Katz et al
1786
International Journal of Obesity
methods of data abstraction (with quality assessment) for
consistency, we did not rely on Community Guide criteria
for recommending interventions. However, the addition of
several high-quality studies published since the initial review
would likely have allowed for formal recommendations.
The additional studies provided sufficient data to take a
meta-analytic approach.
The robustness of these findings is limited, as there is a
high degree of heterogeneity as measured by w
2
or I
2
. The
consistency of a meta-analysis depends on the similarity of
magnitude of the treatment effects of the trials included in
the analysis. To critically appraise these findings, the
presence of any underlying potential source of heterogeneity
has to be explored.
59
Typically, heterogeneity is associated
with reporting bias, differences in the intensity or duration
of interventions, the underlying risk, the effect size and
irregularities of data.
This meta-analysis helps to address uncertainty about the
utility of school-based interventions to combat the child-
hood obesity epidemic. Although behavioral programs
directed at weight control in schools may eventually prove
to be less critical than the establishment of school policies
and environmental modifications that promote health
behavior change (without requiring significant motivation
on the part of the student), most have in fact demonstrated
success.
57
In these analyses, we observed a pooled effect size
of 0.29 in clusters of studies using combination nutrition
and physical activity interventions. This effect size corres-
ponds to 21.3% non-overlap between the intervention and
the control conditions according to Cohen’s interpretation.
60
Results of the analyses of studies using TV reduction, nutrition
alone and physical activity alone should be interpreted
cautiously, as only one study was available in each category.
Nevertheless, these results indicate that the major contributing
factor to the success of combination nutrition and physical
activity interventions may be the nutrition component. The
extent to which physical activity interventions contributed to
weight reduction was minimal. However, it is important to
consider that lack of evidence of effectiveness is not the same as
evidence of ineffectiveness. Too few studies were available to
adequately evaluate these strategies. Heterogeneity of outcome
measures is compounded by heterogeneity of intervention
methods and, to a lesser extent, populations, thus rendering the
aggregation of data and findings challenging.
Ideally schools should be provided with information on
the exact elements that make an obesity prevention or
control program effective. Given that intervention compo-
nents vary considerably across studies, it is not possible to
do so definitively; however, several salient considerations
emerge from this review. An assessment limited to the
findings of formal meta-analysis suggests that the following
commonly used program components may be valuable:
parent involvement (as discussed above),
37–41,43,44
classroom
(or after-school) instruction on improving dietary intake
or increasing PA,
37–41,43,44,46,49
participatory/hands-on,
skill building student activities,
37–41,43,44,49
the provision of
print materials,
37–40
teacher training for program imple-
mentation,
37–39
student competitions,
44
improvements to
the nutritional environment (school cafeteria offerings,
etc.),
43,46
implementation of PA programs in addition to
routine PE,
40,41,43
modifications to duration, frequency or
intensity of existing PE,
46,49
use of non-competitive PA,
49
training in behavioral techniques (including self moni-
toring, goal setting, etc.) or coping skills (decreasing
irrational thoughts, improving self-talk, etc.)
38,39,41,49
and
program tailoring for cultural relevance.
41,43
Future studies
should examine strategies for the optimal blending of these
intervention approaches.
School policies and programs going forward should be
informed by the evidence available to date, but not limited by
it. Consistent patterns not yet assessable by meta-analysis
have emerged. Weaving nutrition, physical activity or
TV reduction lessons into the standard curriculum, so that
key messages are reinforced in multiple contexts, appears
useful.
50
Programs appear to have been enhanced when
physical activity was not merely encouraged, but made a
routine part of the school day.
45,51,53
Very few studies focusing
on TV reduction were available at the time this review was
conducted
52,55
and only one was amenable to computation of
effect size.
55
This strategy remains appealing despite the
relative paucity of data and deserves further attention.
Television viewing likely imposes four interrelated adverse
effects related to weight control in children. First, time spent
viewing TV is sedentary, and thus conducive to energy
imbalance. Second, it has long been hypothesized that TV
displaces other, more active leisure pursuits from a child’s
day,
58
and thus it represents both the addition of sedentary
time and the subtraction of active time. Third, snacking
while watching TV is common. In a recent study of the
affects of food advertising during children’s television
programs, 90% of 3- to 8-year-olds ate while watching TV,
and the majority of foods consumed were snack foods of low
nutritional value.
59
This and other studies provide evidence
that TV exposes children to frequent advertisements for fast
food, and high sugar, high salt, high-fat ‘junk food of low
nutritional value. These advertisements directly affect eating
habits in the short termFa majority of children ask their
parents for foods seen on TV
59
and potentially in the long
term, as food-marketing strategies focus on creating lifelong
customers.
61
For these reasons, reducing TV viewing should
have favorable effects on energy balance.
Interventions that modify school policies and the physical
environment in ways that support improved dietary prac-
tices and regular physical activity, but do not provide
behavioral programs, are absent from this review. Few policy
or environmental interventions were candidates for inclu-
sion simply because those published at the time of the review
did not report measurement of weight-related outcomes.
These types of strategies to combat childhood obesity are
gaining political support and are expected to make a
significant impact. Adoption of such approaches, with
concurrent evaluation, is warranted.
Strategies for prevention and control of obesity
DL Katz et al
1787
International Journal of Obesity
The conclusions drawn from this meta-analysis are con-
sistent with those reported in previous systematic reviews.
We found that combination interventions (nutrition and
PA) with a parent or family component produced significant
weight reduction. This result is supported by a recent meta-
analysis of seven intervention studies on weight loss for
overweight children.
23
The authors reported a significant
weight loss effect of diet, physical activity and parental
involvement in all seven studies. Another review found that
17 of 25 studies resulted in statistically significant reduction
in BMI.
20
On the other hand, results from interventions
aimed at obesity prevention have not been as promising.
A recent meta-analytic review of 64 obesity prevention
programs (46 trials) for children and adolescents showed
that 79% of programs did not produce statistically reliable
weight-gain-prevention effects.
60
Another systematic review
examining interventions for childhood obesity prevention
also reported that the majority of studies reviewed did
not have a significant impact.
22
These results suggest
that the demonstration of weight loss among overweight
children may be more easily attainable than the demons-
tration of the prevention of weight gain. As noted above,
this review combined intervention and prevention studies,
as the strategies used are substantially the same in both cases.
This study does not provide definitive guidance toward the
optimal school-based strategies for obesity prevention and
control. It does, however, provide hopeful evidence that
progress toward such guidance is being made. No single
intervention, in school or elsewhere, is likely to be sufficient
to reverse the childhood obesity trend. Epidemic obesity has
been created by a veritable flood tide of obesigenic factors in
our society, from fast food to labor-saving technology.
In schools, the increasing availability of highly palatable
foods of questionable nutritional properties has occurred
in tandem with reduced physical activity, in part because of
federal legislation,
62,63
reflecting the adverse influences on
both sides of the energy balance equation that have played
out in society at large. Only when an array of strategies
commensurate with and opposite to the prevailing obesi-
genic influences have been aligned can we reasonably hope
to see epidemic obesity begin to subside. To turn the tide
of epidemic obesity we will likely need to combine many
strategies in schools, communities, clinics, worksites and
households. This article offers guidance for the important
contribution schools can and should make to that systematic
effort.
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    • "Outcomes of these studies included changes in body fat, weight and/or waist circumference, or school environment changes such as lower fat and sodium content of school meals and optimized physical education classes that lead to an increase in time that students are vigorously active. The majority of these highly controlled interventions had modest changes in out- comes [28][29][30]. A program like FUTP60 may be a good adjunct to these more intensive programs, reinforcing key messages through the school environment , and having students participate in school changes. "
    [Show abstract] [Hide abstract] ABSTRACT: Background: Most schools have not fully implemented wellness policies, and those that have rarely incorporate meaningful student participation. The aim of the Fuel Up to Play 60 (FUTP60) program is to help schools implement wellness policies by engaging students in activities to improve access to healthful, good tasting food and drinks, and increase the number and type of opportunities for students to be physically active. The aim of this paper is to present initial student-level results from an implementation of FUTP60 in 72 schools, grades 6-9. Methods: The study used a non-controlled pretest/posttest with serial cross-sectional data. School process data and student-level data were collected in fall 2009 (pre-intervention) and spring 2010 (post-intervention). School wellness practices were captured during a baseline needs assessment survey. Validated self-administered questionnaires assessing dietary and physical activity (PA) behaviors were administered to students in grades 6-9 in the 72 pilot schools. Mixed-effects logistic regression controlling for clustering of schools and demographics was used to calculate odds ratios and confidence intervals to evaluate changes pre- and post- intervention. Results: All 72 schools implemented FUTP60 during the 2009-2010 school year. Action strategies most frequently chosen by the schools included increasing breakfast participation and new activities before and after school. Positive and significant changes in students' behaviors (n = 32,482 at pretest and 29,839 at post-test) were noted for dairy, whole grains, fruit, and vegetable consumption and PA levels pre- and post-intervention (OR 1.05 to 1.27). Students aware of the program at post-test were significantly more likely to report healthier eating and PA behaviors than students unaware of the program (OR 1.1 to 1.34). Conclusions: FUTP60 pilot findings indicate that a low intensity program focused on wellness policy implementation is associated with small positive changes in student behaviors, especially when students were aware of the program. Although these initial results are promising, a more rigorous controlled study is warranted as a next step.
    Full-text · Article · Dec 2016
    • "Therefore, it is important to determine effective interventions on developing a healthier lifestyle for pregnant women in order to improve maternal and fetal health and bring current or possible obesity and related health problems under control789. Interventions focusing on diet, physical activity, and weight gain and aiming to develop a healthier lifestyle are known to be effective in preventing and controlling obesity [10]. However, the effect of these interventions (dietary intervention with or without increased physical activity) in controlling GWG and decreasing PWR among pregnant women is not clear [8,11121314151617181920. "
    Article · Dec 2016
    • "Increasing exercise sessions and developing physical activity skills during the school week were among the promising intervention for obesity (Waters et al., 2011). Any programmes that emphasise on both nutrition and physical activity seem to be more efficient at reducing children's BMI than those that focus on physical activity alone (Katz et al., 2008). "
    [Show abstract] [Hide abstract] ABSTRACT: The schools environment might be one of the factors that contribute to childhood obesity since children spent most of their time at school. This study aimed to identify the compliance of selected schools in Selangor, Malaysia with whole-school mapping framework and prevalence of obesity among primary school children in rural and urban environmental settings. A total of 1200 children aged 10-11 years from 60 schools in rural and urban area in Selangor involved in this study and their BMI was calculated. The compliance of each school environmental factors was determined by using whole-school environmental mapping framework's questionnaires.© 2016 The Authors. Published by e-International Publishing House, Ltd., UK. Peer–review under responsibility of AMER (Association of Malaysian Environment-Behaviour Researchers), ABRA (Association of Behavioural Researchers on Asians) and cE-Bs (Centre for Environment-Behaviour Studies, Faculty of Architecture, Planning & Surveying, Universiti Teknologi MARA, Malaysia.Keywords: Childhood obesity; whole-school environmental mapping; BMI status; rural and urban settings
    Article · Jun 2016
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