Evidence of an Intervention on Childhood BMI z Score Clinical Trial
The purpose of this study is to assess the effects of a six months nutrition intervention,
delivered and taught by classroom teachers with in-service nutrition training, on the
prevention of overweight and obesity among children in grades 1 to 4.
In this randomized controlled trial, 464 children from seven elementary schools were
allocated to a six months nutrition educational intervention by their own teachers or to
standard care. Intervened teachers had 12 sessions of three hours each with the researchers
throughout six months, according to the following topics: nutrition and healthy eating
(sessions 1 to 4); the importance of drinking water (session 5); strategies to encourage
fruits and vegetables consumption and to decrease high energy-density foods intake (sessions
6 to 8); strategies to increase physical activity (sessions 9 and 10); and healthy cooking
activities (sessions 11 and 12). After each session, teachers were encouraged to develop
activities in class that focused on the learned topics. Sociodemographic, anthropometric,
dietary, and physical activity assessments were performed at baseline and the end of
intervention.
We expect that fewer intervened children become overweight and the consumption of fruit and
vegetables will be higher. In addition, we expect a less consumption of low-nutrition high
dense foods.
We also expect to provide further support to decrease overweight epidemic, involving
classroom teachers in a training intervention and making them dedicated interventionists.
The prevalence of obesity continues to increase (Ogden et al., 2006) and is growing concerns
in Portugal and in the world. As successful treatments have been elusive, the prevention
should be considered a high priority. So, present efforts are being dedicated to develop and
implement overweight and obesity prevention interventions (Gortmaker, et al, 1999; James,
Tomas & Kerr, 2004), in the hope that multilevel approach, if occur early in childhood, may
improve eating habits and physical activity and therefore, contribute to prevent or reverse
this epidemic state.
In each school, previously trained persons performed anthropometric evaluation, using
standardized procedures (WHO Expert Commitee 1995). Anthropometric measurements were
performed in children with light indoor clothing and barefooted. Weight was measured in an
electronic scale, with an error of ±100g (Seca, Model 703, Germany), and height was measured
using a stadiometer, with the head in the Frankfort plane. BMI was computed as mass,
Kg/height, m2. The prevalence of underweight, normal weight, overweight and obesity was
calculated according to the International Obesity Task Force (IOTF) criteria, making a
correspondence between the traditional adult cut-off and specific values for children
according to gender and age (Cole et al. 2000). A z-score (the number of standard deviations
(SD) from the reference population) was calculated for each child using the LMS method and
the calculation was determined using the LMS growth add-in for excel (Pan and Cole 2009).
Dietary intake was gathered by 24h dietary recalls obtained by nutritionists and/or trained
interviewers. We assessed a single recall before and another after the intervention. The
respondents had no prior notification of when the recalls would occur. Training of
interviewers included practice using photos and food models to quantify portion sizes,
experience in probing information from children without suggesting responses as well as the
type of food consumed in detail of fat content, brand name, constituents of mixed dishes and
so on. The 24h dietary recall is the most commonly used dietary assessment method because it
is easy to administer, can be performed in large-scale studies (Kranz and Sie-Riz 2002,
Gomez-Martínez et al. 2009), and can be used to assess adequacy of energy and macronutrient
intakes. During the 24h dietary recall, each child was asked to recall all food and
beverages consumed during the past 24h. Daily routines were used as prompts (waking up,
going to bed, time between classes, and before or after school) to enhance recall. Portion
sizes of foods and beverages consumed were also estimated using food models, photos and
other props (cups, glasses, food wrappers or containers) as an aid in determining serving
sizes. Energy and nutritional intake were estimated using an adapted Portuguese version of
the nutritional analysis software Food Processor Plus (ESHA Research Inc., Salem, OR, USA).
The 24-hour dietary recall interviews captured the time and name of each eating occasion,
the foods and beverages reported at each eating occasion, and the source from which item was
obtained.
In order to assess the level of physical activity of children, parents were asked five
questions with four answer choices (4-point scale) ranging from 0 (very seldom) to 4 (very
often): a) Outside the school does your child take part in organized sport? b) Outside
school does your child take part in non-organized sport? c) Outside school, how many times a
week does your child take part in sport or physical activity for at least 20 minutes? d)
Outside school hours, how many hours a week does your child usually take part in physical
activity so much that he gets out of breath or sweat? e) Does your child take part in
competitive sport? (Mota and Esculcas 2002). The total sum of the points was computed
reaching a maximum of 20 points. To express the activity levels, a Physical Activity Index
was obtained, which divided the sample into four activity classes: sedentary group (0-5);
low activity group (6-10); moderately active group (11-15); and vigorously active group
(16-20), on the basis of their reported physical activity (Mota and Esculcas 2002).
Social, demographic and family characteristics were assessed by questionnaire. The survey
sent to parents contained questions about gender and age of children, education of the
parents (recorded in five categories: 0, 1-4, 5-9, 10-12, and more than 12 years of formal
education). This information was further grouped for analysis into three categories: up to 9
years, 10-12 years, and more than 12 years of education.
The research team proposed, in January 2008, the accreditation of the sessions that were
developed with the teachers to the Minister of Education, Scientific-Pedagogic Council for
In-service Training (Conselho Científico Pedagógico da Formação Contínua, Ministério da
Educação). This proposal was approved in September 2008 in the form of "training workshop"
with 72 hours duration, distributed by active learning strategies (36 hours) and work
contact with the children (36 hours). Teachers of the intervention group had 12 sessions of
three hours each with the researchers throughout six months, which included the following
topics: nutrition and healthy eating for the children and the families (sessions 1 to 4);
the importance of the water (session 5); strategies to encourage fruits and vegetables
consumption and to decrease high energy density foods intake (sessions 6 to 8); to increase
physical activity and to reduce screen time exposure (sessions 9 and 10); and healthy
cooking (sessions 11 and 12). After each session, teachers resend the learned contents to
develop creative and engaging classroom activities about the addressed topic. All the
questions that arose during the implementation of classroom activities were addressed and
resolved shortly with the researchers. Teachers were allowed to develop and refine the
activities and learning strategies that were proposed by researchers. At the end of this
period, the teachers delivered a critical report of activities focused on the work contact
with children.
The data analysis was performed using SPSS ®, Version 18.0 (SPSS Inc; Chicago, IL).
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Allocation: Randomized, Endpoint Classification: Efficacy Study, Intervention Model: Factorial Assignment, Masking: Double Blind (Subject, Outcomes Assessor), Primary Purpose: Prevention