Modifications in the Eating Habits of Adolescents of Secondary Education as a Result of a Nutritional Intervention
Condition: Food Habits
Study type: Interventional

Summary: 
      The objective of the study was to demonstrate the efficacy of a nutritional intervention
      based on the Social Cognitive Theory and the Transtheoric Model in the favorable modification
      of eating habits in adolescents of secondary education.

      The hypothesis was that secondary school adolescents receiving a nutritional intervention
      based on Social Cognitive Theory and the Transtheoric Model presented more favorable
      modifications in their eating habits than adolescents who only received nutritional
      information.

      A community trial was conducted with pilot testing for the validation of the study
      instruments. Adolescents from the second grade of the afternoon shift of the Jalisco
      Technical High School Nº46 participated in the 2015-2016 cycle.

      Self-completed questionnaires evaluated socioeconomic variables, physical activity habits,
      stage of change (Transtheoric Model), constructs of the Social Cognitive Theory and five
      eating habits: consumption of fruits and vegetables, natural water, dairy products, sugary
      drinks and processed foods ; As well as anthropometric variables.

      The intervention group had twelve workshops on healthy eating habits and two sessions for
      parents. The control group received three sessions of nutritional information.

      All variables were measured again at the end of the intervention to evaluate results in the
      short term and three months later to know results in the medium term.
    

Detailed description: 
      DESCRIPTION OF THE DESIGN: The present study is a community trial, since there was control
      group and intervention group, random group assignment, intervention at group level, pre-test
      and at least one post-test (López, 2011).

      The study counted with pre-test or initial evaluation - evaluation 1 (E1) and two post-tests:

      Evaluation 2 (E2) in the short term, at the end of the intervention (approx 4 months after
      evaluation 1).

      Evaluation 3 (E3) in the medium term, three months after the intervention. Prior to the
      community trial, the validation study of the instruments used in the research was carried
      out. For this, the questionnaires were applied to adolescents twice (Evaluation A-EA and
      Evaluation B-EB), with a temporal difference of one week.

      CALCULATION OF SAMPLE SIZE:

      The sample size calculation for the intervention group and the control group was based on the
      data obtained in the Birnbaum et al. to the. (2002) regarding the variable "changes in the
      average number of servings consumed per day of fruits and vegetables". This was the only
      study that was found to measure changes in dietary habits (food consumption) in a
      quantitative way, as planned in the present study.

      Was used the "formula to calculate sample size when is expected to find an average difference
      and is known the standard deviation, given reliability and power (considering different
      variances)." A control ratio was established: cases of 1: 1, a level of significance or
      probability of error type 1 (α) of 0.05 (reliability of 95%) and a probability of error type
      2 (β) of 0.20 (power of 80 %).

      The following results were obtained: Sample size for each group 29

      SAMPLING SYSTEM:

      The sampling system for group formation is non-probabilistic, since the groups were already
      formed prior to the experiment (2nd grade school groups). However, the form of participation
      of the school groups in the research, yes was assigned of simple random way (by means of
      tombola).

      Of the six groups corresponding to the 2nd grade school, two groups were randomly selected to
      perform the validation of the instruments (stage 1 of the research).

      The remaining four groups participated in the other stages of the research. After completion
      of evaluation 1, they were randomly assigned to either the intervention group (two groups) or
      the control group (two groups).

      CRITERIA AND STRATEGIES OF FIELD WORK:

      PREVIOUS ACTIVITIES. Presentation of the project to the directors of the educational
      institution. Organization of times and schedules with the institution. Signature of informed
      consent for managers of the educational institution.

      Random selection of groups that will participate in stage 1 of the research. STAGE 1.
      Validation of the instruments in the study population. Presentation with parents of
      adolescents participating in the so-called "validation group" and explanation of procedures,
      delivery and signing of informed consent.

      Presentation with adolescents participating in the so-called "validation group" and
      explanation of procedures, delivery and signing of informed consent.

      Application of questionnaires (Evaluation A). One week later, the second application of
      questionnaires (Evaluation B). Taking anthropometric measurements. Delivery of results
      (nutritional status and eating habits) and educational material (triptych) on healthy eating
      habits of participating adolescents.

      STAGE 2. Recruitment for the community trial and Evaluation 1. Presentation with parents of
      adolescents participating in the "intervention group" or in the "control group" and
      explanation of procedures, signed informed consent.

      Presentation with the adolescents who participate in the "intervention group" or in the
      "control group" and explanation of procedures, informed consent sign.

      Application of questionnaires in both groups. Measurement of anthropometric measures in both
      groups. Random selection of groups participating in the "intervention group" and the "control
      group".

      Delivery of results (nutritional status and eating habits) to students and parents of both
      groups.

      STAGE 3. Intervention. Note: simultaneous activities in both groups. STAGE 4. Evaluation 2
      (at the end of the intervention). Application of questionnaires in control group and
      intervention group. Anthropometric measures taken to control group and intervention group.
      Delivery of results to students and parents of both groups. STAGE 5. Evaluation 3 (three
      months after evaluation 2). Application of questionnaires in control group and intervention
      group. Anthropometric measures taken to control group and intervention group. Delivery of
      results to students and parents of both groups. Delivery of report of global results to
      executives of the educational institution.

      MEASUREMENT TOOLS:

      Questionnaires. General data format: It was elaborated to collect the necessary data to
      describe the population, it includes aspects related to data of identification, sex, age,
      socioeconomic level, habits of physical activity and measures and anthropometric indices. To
      evaluate the socioeconomic level, there are six multiple-choice or open-ended questions,
      which were adapted from validated questionnaires (AMAI, 2017; Bauce, 2010; Vera-Romero,
      2013); Only those that were adequate for adolescents to be answered were included. To
      evaluate physical activity, a section of a validated questionnaire is used (Flores-Vázquez,
      2014), with slight adaptations. To ensure the validity, the internal consistency and
      reproducibility of said sections were evaluated. Only the anthropometric evaluation section
      is filled by the evaluator and not by the adolescent.

      Self-completed food habits questionnaire: Contains 20 open-ended questions about the
      frequency and amount of consumption of fruits and vegetables, dairy products, natural water,
      sugary drinks and industrialized foods. Some of the questions were extracted from a validated
      questionnaire (Flores-Vázquez, 2014), however, due to the adaptations and added questions,
      the reproducibility of the questionnaire was evaluated.

      Cognitive social measures related to eating habits in adolescents: Evaluates self-efficacy,
      facilitating resources, self-regulation, social support, expectations and self-assessment of
      expectations in relation to eating habits, using Likert type scales, including a total of 28
      questions Four to five for each section). The instrument was translated and adapted from a
      previously validated one (Dewar, 2012). The validation of the resulting instrument was
      previously performed, for which reproducibility, internal consistency and factor load were
      evaluated.

      Algorithm to measure stage of change: It consists of a total of 4 linked questions about
      actions and intentions in healthy eating habits, through which the adolescent change stage is
      obtained, is based on an algorithm previously translated into Spanish (Villalobos, 2012).
      Their reproducibility and clarity were evaluated for the adolescent, as well as their
      correlation with the amount of adequate eating habits (criterion validity).

      CAPTURE OF THE DATA:

      Anthropometric measurements. They were performed by nutrients previously trained and
      standardized in the anthropometric measurements. One evaluator performed the measurement of
      body weight and height and another the one of waist and abdominal perimeter; Another person
      served as a scorer.

      Questionnaires. All questionnaires were designed to be autocompleted. For their application,
      the evaluators gave the questionnaires to the students and indicated the importance of
      providing accurate information about the questions included in the formats. Each
      questionnaire has explicit instructions on how to complete it. However, the evaluators
      remained with the students during the filling of the instruments and solved the doubts. It
      took 30 minutes to complete the questionnaires.

      DATABASE AND COMPUTER PROGRAMS:

      The preparation of the thesis document was carried out in the program Microsoft Office Word
      2013. The database was elaborated in the program Microsoft Office Excel 2013 and later
      exported to the statistical program SPSS version 22, for its analysis. The calculation of the
      anthropometric indices was done through the WHO Anthro Plus program

      STATISTIC ANALYSIS:

      Quantitative variables are expressed in quartiles (non-parametric) or some in mean and
      standard deviation (parametric). The qualitative variables are expressed in frequency and
      percentage. Non-parametric tests were used for the qualitative variables. It was verified
      whether the quantitative data are normally distributed by means of the Kolmogorov-Smirnov (n>
      50) or Shapiro-Wilk (n≤50) test, which allowed the use of parametric or non-parametric tests
      (Table 13) .

      Intra-group tests. Quantitative variables: Student's parametric T test for related samples,
      Wilcoxon non-parametric test. - Evaluate changes in food consumption (portions / day) in the
      short term (evaluation 1 to 2) and medium term (evaluation 1 to 3) in the intervention group
      and in the control group. -Evaluate modifications in the score of each TCS construct, in the
      short and medium term, in each group. -Evaluate changes in the anthropometric indicators, in
      the short and medium term, in each group.

      Ordinal qualitative variables: Wilcoxon non-parametric test -Evaluate differences in the
      change stage, in the short and medium term, in each group. - Evaluate differences in the
      distribution of nutritional status, in the short and medium term, in each group. -Evaluate
      differences in the distribution of the food habit "dairy consumption", in the short and
      medium term, in each group. -Evaluate differences in the distribution of the answers of the
      questions about cognitive-social measures, in the short and medium term, in each group.

      Dichotomous qualitative variables: Non-parametric test Mc Nemar -Evaluate differences in the
      distribution of each food habit classified as "adequate or inadequate", in the short and
      medium term, in each group. -Evaluate differences in the presence of abdominal obesity, short
      stature and overweight / obesity, in the short and medium term, in each group.

      Intergroup testing. Quantitative variables: Student's T parametric test for independent
      samples, Non-parametric test U of Mann Whitney - To compare each eating habit, TCS construct
      and anthropometric indicator, in each evaluation, between the intervention group and the
      control group. -Compare the difference in the modification of each eating habit, in the short
      and medium term, between the intervention group and the control group. -Compare the
      difference in the modification of each TCS construct, in the short and medium term, between
      the intervention group and the control group. -Compare the difference in the modification of
      each anthropometric indicator, in the short and medium term, between the intervention group
      and the control group.

      Qualitative variables: Non-parametric test Chi-square test or Fisher's exact test - Compare
      the distribution in the socioeconomic level and physical activity habits (baseline), of the
      intervention group vs the control group. -Compare the distribution in the nutritional status
      and the stage of change, in each evaluation, of the intervention group vs the control group.
      -Compare the distribution of each food habit classified as "adequate or inadequate", in each
      evaluation, of the intervention group vs the control group. -Compare the changes in the stage
      of change, in the short and medium term, of the intervention group vs the control group.
    

Intervention name(s): Nutritional intervention based on the SCT and the TM; Nutritional information
Intervention type(s): Behavioral; Behavioral
Intervention description(s): Nutritional workshop based on the Cognitive Social Theory and the Transtheorical Model: twelve group sessions (one per week) lasting 40 minutes each, aimed at adolescents; With delivery of printed material to work at home (workbook); And two sessions (every month and a half) addressed to parents.; Three informative sessions of 25 minutes (one each month) on healthy eating habits and delivery of educational material to adolescents.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: Food Habits; Adolescents; Educative Intervention; Nutrition Assessment; Behavior Modifications