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Pinki Sahota a School of
Health Sciences, Leeds Metropolitan University, Leeds LS1 3HE, b Leeds Community and Mental Health Trust, Belmont
House, Leeds LS2 9DE, c School of Medicine, Leeds University,
Leeds LS2 9LT, d Leeds General Infirmary, Leeds LS1 3EX, e Nuffield Institute of Health,
Leeds LS2 9PL Correspondence to: M C J Rudolf Mary.Rudolf{at}leedsth.nhs.uk
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Abstract |
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Objective:
To assess if a school based intervention
was effective in reducing risk factors for obesity.
Design:
Group randomised controlled trial.
Setting:
10 primary schools in Leeds.
Participants:
634 children aged 7-11 years.
Intervention:
Teacher training, modification of school
meals, and the development of school action plans targeting the
curriculum, physical education, tuck shops, and playground activities.
Main outcome measures:
Body mass index, diet, physical
activity, and psychological state.
Results:
Vegetable consumption by 24 hour recall was higher in children in the intervention group than the control group
(weighted mean difference 0.3 portions/day, 95% confidence interval
0.2 to 0.4), representing a difference equivalent to 50% of baseline
consumption. Fruit consumption was lower in obese children in the
intervention group (
1.0,
1.8 to
0.2) than those in the control
group. The three day diary showed higher consumption of high sugar
foods (0.8, 0.1 to 1.6)) among overweight children in the intervention
group than the control group. Sedentary behaviour was higher in
overweight children in the intervention group (0.3, 0.0 to 0.7). Global
self worth was higher in obese children in the intervention group (0.3, 0.3 to 0.6). There was no difference in body mass index, other
psychological measures, or dieting behaviour between the groups. Focus
groups indicated higher levels of self reported behaviour change,
understanding, and knowledge among children who had received the intervention.
Conclusion:
Although it was successful in producing
changes at school level, the programme had little effect on children's behaviour other than a modest increase in consumption of vegetables.
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What is already known on this topic
What this study adds
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Introduction |
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School staff have access to large numbers of children in an environment that has the potential to support healthy behaviour and is favourable for the delivery of health promotion programmes.1 Primary schools are particularly suitable for such programmes as children in this age group are responsive to health messages and behavioural changes may be maintained into adolescence and adulthood.2
Recent reports have indicated that over 17% of 11 year old children are obese and 30% overweight.3 School based programmes might be able to reverse the increase in obesity. Programmes targeted at obese children and adolescents have reported positive results, particularly those aimed at primary school aged children4 and those combining diet and exercise with parental involvement. However, most of these studies not only had inadequate methods5 but also had the problem that they targeted obese children (often volunteered by parents). Such targeting may increase stigmatisation of children at school.
An alternative strategy is to implement a health promotion programme aimed at all pupils or pupils at high risk of becoming overweight rather than at those who are already obese. Again, these initiatives have met with some success,5 although outcomes assessed in terms of change in weight or body fat are generally not as robust as those in studies targeted solely at obese pupils.
Only a few primary prevention studies of school based interventions
haven been reported from the United States,6 and none in
the United Kingdom.7 We designed a multicomponent health promotion programme, based on the Health Promoting Schools
concept,8 aimed at reducing risk factors for obesity in
primary schools. It was devised as a group randomised trial so that its
effect could be appropriately assessed. We targeted children aged 8-10 because they were cognitively able to complete questionnaires and
because levels of obesity start to rise around this age.3
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Participants and methods |
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We recruited 10 primary schools in Leeds and paired them according
to size, ethnicity, and level of social disadvantage (as reflected by
numbers of free school meals). We randomised them to receive the
intervention or to serve as the comparison school using the toss of a
coin. A power calculation indicated that with five schools in each arm,
the study would have 80% power to detect an underlying difference in
means of a normally distributed outcome measure of
1.8 standard
deviations at the 5% significance level and 65% power to detect a
difference of 1.5 SD. This took into account the cluster randomisation design.
All the participating schools were state primary schools sited outside the inner city area. Sociodemographic measures suggested that the schools' populations generally reflected the Leeds school aged population, although there was a slight bias towards more advantaged children. The schools had 1-42% children from ethnic minorities and 7-29% entitled to free school meals compared with 11% and 25% respectively for Leeds children as a whole.
The intervention schools received the active programme promoting lifestyle education in schools (APPLES) (box). The programme consisted of teacher training, modifications of school meals, and the development and implementation of school action plans designed to promote healthy eating and physical activity over one academic year (September 1996-July 1997). The comparison schools continued with their usual health curriculum, without the intervention. The philosophy and details of the intervention are described in the accompanying paper, together with an evaluation of the implementation and effect of the programme.9 The study was approved by the local research ethics committee and the schools' governing bodies. Parental consent was also obtained.
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Active programme promoting lifestyle in schools (APPLES)
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Main outcome measures
We assessed the effect of the intervention on individual behaviour
by collecting data on growth, diet, physical activity, and
psychological state at baseline (June-July 1996) and 12 months later.
These measures could not be obtained blind to the schools'
intervention status.
Children were measured in school by
the same expert auxologist. Weights were without shoes, jumpers, or
sweatshirts and were recorded to within 0.1 kg with Seca 835 portable
digital scales. Heights were measured by a standard
method9 and recorded to an accuracy of 1 mm with a free
standing Magnimeter stadiometer with rigid tripod mounting (Raven,
Dunmow). We then calculated body mass index (weight in kilograms
divided by the square of height in metres).
Dietary information was assessed by both 24 hour recall and
three day food diaries. Recall was based on a checklist in which possible foods for each of the meals eaten during the day were listed,
with an option to record foods not listed. The diary was free form. We
analysed the information from both methods for frequency of consumption
of foods high in fat, foods and drinks high in sugars, fruit, and vegetables.
Physical activity
The frequency of physical activity and
sedentary behaviour was measured by questionnaire and was
categorised by frequency of sport and physical activity during the past
week (sport outside school, swimming, going for a walk, attending any club or activity where they were active, playing outside) and frequency
of sedentary behaviour in past 24 hours (watching television and
playing on the computer).
Psychological measures
We used three validated tools to
evaluate the effect of the intervention on psychological well being: the self perception profile for children, a 36 item questionnaire with
six subscales that distinguish global self worth from competence in
five specific domains10; a measure of dietary restraint
that has been used in children aged 811; and the adapted
body shape perception scale, which consists of a series of seven line
drawings ranging from extremely thin to obese for self assessment of
the individual's perception of their body size.12 The
psychological data were categorised into three parts: the child's self
perception, eating behaviour score (0-12) reflecting the extent of
dieting behaviour; and body shape preference score reflecting the
degree of satisfaction with body image.
To determine the effect on children's levels of knowledge and
attitudes towards healthy living, 80 focus groups involving 320 children were held at the end of year. They were conducted by two
researchers blind to the schools' allocation using an interview guide
with stimulus photographs of four typical meals of the day. A method of
scoring was developed to measure level of knowledge and self reported
changes in diet and physical activity.
Analysis of data
We applied a multilevel statistical model using
STATA13 to assess changes in body mass index, diet,
physical activity, and psychological well being. This statistical model took into account the pairing and lack of independence among subjects within the school, known as the clustering effect. This was achieved by
treating the analysis as a random effect meta-analysis across cluster
pairs.14 In addition, we adjusted for the characteristics of the individuals (sex, age, baseline body mass index, and outcome of
interest at baseline) and the intervention status of the five pairs of
schools. The analysis was based on only those children measured both at
baseline and at one year.
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Results |
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Characteristics of sample
In all, 636 children (314 intervention, 322 comparison) took part
in the evaluation. The mean (SD) age of children in the intervention
schools was 8.4 (0.63) years, with 145 (46%) entering school year 4 and 169 (54%) year 5. The mean age of the children in the comparison
schools was also 8.4 (0.63) years, with 145 (45%) entering year 4 and
177 (55%) year 5. Table 1 shows the baseline characteristics of
the sample in terms of growth measures, diet, and physical activity and
table 2 their psychological scores. No significant differences
were found between the intervention and comparison pupils for any of
the measures.
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Completion rate
All 10 schools completed the project. The figure shows the
progress of the schools through the trial. Only 21 children declined to
participate in the data collection. Over the year, 42 children left and
40 new children joined. In all, 613 (97%) children were measured at
baseline and 595 (94%) at the end of the intervention period; 404 (63%) completed three day food and physical activity diaries at
baseline and 407 (64%) at the end of the study.
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Growth
Table 3 shows the weighted mean difference in body mass index
standard deviation score for the five pairs of schools. Overall, there
was no difference in score between the intervention and control
children at the end of the year. There was also no difference for the
overweight (weighted mean difference
0.07, 95% confidence interval
0.22 to 0.08) or the obese children (
0.05,
0.22 to
0.11).
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Diet
Analysis of 24 hour recall showed that the intervention children
had higher vegetable intakes at the end of the study (tables 3 and
4). The weighted mean difference of 0.3 (95% confidence interval 0.2 to 0.4) indicates on average one third of a portion more a day. As the
mean baseline was only 0.6 portions/child/day, this difference is
equivalent to 50% of baseline intake. The same difference was seen for
the overweight (0.3, 0.1 to 0.5) and obese children (0.3,
0.1 to
0.6). The three day diary (which had a quantitatively and qualitatively
lower completion rate) did not show these
differences.
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Physical activity and psychological measures
We found no significant difference in physical activity or
sedentary behaviour for the sample as a whole. Sedentary behaviour
increased by one third in the overweight children in the intervention
group compared with overweight control children. The only significant
difference in psychological measures was a small increase in global
self worth for obese children in the intervention schools (0.32, 0.0 to
0.64).
Focus groups
Compared with children in control schools, children in the
intervention schools had higher levels of self reported behaviour
change, greater understanding of the health benefits of diet and
physical activity, and increased sophistication of ideas and
vocabulary, willingness and confidence to share their ideas, and basic
knowledge. They were more able to recollect topics learnt and
activities undertaken in school linked to diet and physical activity.
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Discussion |
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Implementation of this health promotion programme was highly successful,9 and it was therefore disappointing that the children showed minimal behavioural changes. The only clinically important positive result was a modest increase in consumption of vegetables. Vegetables are likely to be the most challenging food group to change in children, and a rise of one third of a vegetable portion per child is a huge increase in vegetables consumption across the city per day. Nevertheless, it is a small return for the effort made.
One possible reason for the apparent lack of effectiveness of the intervention could be the alarming increase in the prevalence of overweight and obesity in this entire school population.3 This rise in body mass index was seen as the children grew older as well as over time. In the face of such an epidemic, a programme with limited resources would be unlikely to have demonstrable effects in countering this increase. Clearly, the social and environmental forces at work require much larger public health counter measures.
Problems of evaluating complex interventions
Lack of evidence of effectiveness does not necessarily mean
evidence of ineffectiveness.16 Inadequate sample size is
often an issue in trials, and this is especially the case in studies
using group randomisation. Although about 600 children participated,
the unit size was only five schools in each arm, which is very small.
More schools are needed to achieve a clear result. This would have been
more costly and difficult to implement. Several larger health promotion
trials have also had results below expectations for the same
reason.17-22
Conclusions
Since the programme was successful in changing the ethos of the
schools and the attitudes of the children,9 it is
premature to conclude that it was unsuccessful in reducing risk factors
for obesity. The intervention was designed for one academic year only,
recognising funding limitations. The intervention might have been
strengthened if the families were targeted more directly,24 while still maintaining the focus on the
school community.
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Acknowledgments |
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We thank the staff, pupils, and parents of Brodetsky, Cookridge, Fir Tree, Horsforth St Mary's, Moortown, Morley The Newlands, Pudsey Lowtown, Shadwell, Springbank, and the Whartons Otley primary schools for their participation, enthusiasm, and support. We also thank Jenny Walker, paediatric endocrine sister for collecting the anthropometric data, and Andy Vail for statistical advice.
Contributors: PS was the project manager and provided the main input into guiding and supporting the schools through the intervention. She collected and analysed the raw data, coordinated the programme, and drafted the article. MCJR was the principal investigator and coordinated the research team. She supervised the analysis and interpretation of the data and wrote the article jointly with PS. She will act as guarantor for the paper. RD provided the health promoting philosophy and guided the approach taken in designing the APPLES programme. She and AJH, JHB, and JC provided support in conducting the research and contributed intellectual input into the ideas behind and final format of the paper.
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Footnotes |
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Funding: The research was funded by a grant from the Northern and Yorkshire Region Research and Development Unit.
Competing interests: None declared.
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(Accepted 12 July 2001)