Title: Effectiveness of Physical Activity Enhancement and Obesity Prevention Programs in Children and Youth
Investigator Name: Helen Thomas
Project Completion Date: March 2004
Research Category: Synthesis
Institution: McMaster University and the Public Health and Community
Services Department, Public Health Research, Education and Development
Program, City of Hamilton
Project Number: 6795-15-2002/4470007
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Summary
The purpose of this systematic literature review is to provide
some national policy direction related to the effectiveness of
interventions for promoting healthy weight, preventing overweight/obesity
and increasing physical activity among school aged children and
youth.
Although the reported rates of childhood obesity/overweight in
Canada vary, they are high. Over the past 15 years, obesity rates
in children have doubled. Similar trends have been noted in Australia
and the United States. Although not all obese/overweight children
become obese adults, many do. As well, many thin children become
obese/overweight adults. Adult obesity is implicated in a number
of chronic illnesses. The costs of obesity to the health care system,
other systems and the individual's quality of life are substantial.
Providing preventive strategies to all children could reduce child
and adult obesity/overweight.
Few population frameworks to guide the interventions to reduce
obesity/overweight have been suggested. Canada and Australia have
proposed similar models to address this issue. The models suggest
there are 3 broad variables involved: biology/genetics, behavioural,
and environmental influences. As well, there are macro and micro
level factors within the variables. Much of the work to date has
focused on the micro factors, primarily on education. Although
there are limitations, schools are good settings for population
based interventions directed at children and youth, their families
and the community.
This review consists of several components. An overall comprehensive
literature search for primary studies between January 1985 and
June 2003 was carried out. The literature was divided into five
topics: improving nutritional intake, reducing physical inactivity,
increasing physical activity, multi-faceted interventions including
improving nutrition, increasing physical activity and impacting
the school environment, and school environmental interventions.
Over 1,100 articles were retrieved. All articles were reviewed
for relevance using standardized criteria. Those that were relevant
(n=425) were then assessed for methodological quality. All relevant
studies are reported in the tables. Only those with strong methodological
rigour are described in the text. One should exercise caution when
viewing the results of the weaker studies as they have several
threats to internal and external validity.
Both Randomized Controlled Trials (RCTs) and cohort studies were
included. The RCTs were, in general, stronger than the cohort studies.
The most frequent limitations of the RCTs included potential selection
bias, lack of blinding of outcome assessors, lack of sample size
calculation, and inappropriate analysis in that many investigators
allocated students by school and then analyzed outcomes by individual.
As well, many investigators did not report the consistency of the
intervention or the amount of the intervention received by study
participants. Few studies provided any long term follow-up to assess
whether positive impacts were sustained. The other difficulty is
that when studies reported statistically significant differences
in outcomes, the actual differences were small and their clinical
significance was unknown.
Although the theory underlying many interventions was not implicitly
stated, it appeared that many were based on either social cognitive
or ecological theory. A few studies were found that used the environ
mental/systems based approach. Although none of these studies met
the relevance criteria for this review, some examples of work in
this area are included in the environmental section as illustrations
of possible future work.
Few studies reported the effect of culture, socioeconomic status
and individual level of risk on outcomes. In attempting to identify
factors contributing to obesity/overweight in children and youth,
several investigators have noted the differences in rates based
on cultural differences and on socioeconomic status. Of these factors,
socioeconomic status may be the most important.
Many of the studies involved elementary school children. About
one third focused on adolescents. The effectiveness of parental
involvement had mixed results. One study demonstrated that teacher
preparation positively impacted on the amount of physical activity
students engaged in during physical education classes. However,
classroom teachers led most of the interventions.
The results of the review are that positive outcomes are modest
at best and many results are inconsistent between studies. Based
on this review of the literature, the following are recommendations
for policy, program delivery and research.
Policy and Program Delivery
- Increasing physical activity during school could be accomplished
by addressing the balance of aerobic activity and skill development
in physical education classes and by increasing the number of
physical education classes, particularly in secondary school.
- The skill and motivation of teachers to comply with model
programs needs to be addressed. Regular teachers who are leading
physical education classes need access/mentoring from specialists
to maximize the amount of physical activity that students receive
during classes.
- Since multi-faceted programs are more effective than others,
the resources for planning, implementing, monitoring and evaluating
these programs should be made available.
- Organizations mandated to fund research in the areas of obesity/overweight
prevention should be discouraged from funding projects that do
not take the identified methodological limitations into account.
- Governments, the private sector and others need to work together
to provide more rigorous evaluation of environment/systems based
interventions.
Research
- Research studies must make the theoretical basis explicit.
Combinations of theories should be encouraged.
- Strategies to reduce selection bias, improve blinding of outcome
assessors, present sample size calculations, reduce analysis
errors, monitor the fidelity of the intervention and report the
amount of the program received by participants need to be included
in future research plans/protocols.
- All analysis (and sample size calculations) should include
subgroup analysis of at least gender, socioeconomic status and
culture to determine their impact on programs.
- Long-term follow-up of successful programs is necessary to
determine the sustainability of positive changes.
- Clinicians and researchers need to work together to determine
a clinically significant difference in both improving nutrition
and increasing physical activity.
- Qualitative methods could improve understanding of the barriers
to improving nutrition and increasing physical activity for children,
their families and the community.
The views expressed herein do not
necessarily represent the views of Health Canada
In addition to the above summary, the full report can be accessed
in the following ways:
- The print version of the full report can be obtained in the
language of submission from the Health Canada Library through
inter-library loan.
- An electronic version of the report in the language of submission is available upon request from Health Canada by contacting the Research Management and Dissemination Division.
This research has been conducted with a financial contribution
from Health Canada's Health Policy Research Program. For permission
to reproduce all or part of the research report, please contact
the Principal Investigator directly at the following address:  thomash@mcmaster.ca.
The Health Policy Research Program (HPRP)
funds research that provides an evidence base for Health Canada's
policy decisions. The HPRP is
a strategic and targeted program with a broad socio-economic orientation
and connections to national and international endeavours. The research
can be primary, secondary or synthesis research, a one-time contribution
to a developing research endeavour, or a workshop, seminar or conference.
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