Design
The Obesity Clinic at Federico Gomez Children's Hospital of Mexico conducted arandomized clinical trial between January 2011 and December 2014 with approval from the hospital’s Research, Ethics and Biosecurity Committee. This study is reported according to the CONSORT guidelines (Additional file 1). After providing written consent, 177 children with obesity (BMI ≥ 95 pc) of age 5-11 years and their mothers were randomly assigned to participate in the intervention group or the control group. None of the participating children were receiving pharmacological treatment for obesity, were morbidly obese or were associated with a genetic syndrome. Mothers of intervention group (n=90) attended six weekly group sessions, lasting 90 minutes. Sessions were taught by nutritionists of the clinical nutrition course who rotate in the Obesity Clinic of this hospital and were standardized in the procedures performed.
(See session content in Table 1).
Table 1. Topics covered in each session with intervention group mothers.
Session
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Content
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1
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Dietary and physical activity habits and their link to obesity and cardio-metabolic diseases. Children learn about healthy eating habits and health risks at home.
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2
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Food-preparation processes. Selecting and purchasing food and beverages; importance of food groups and their impact on health; importance of fruit and vegetables. Balance between food groups, source of foods, organic or industrialized. Family menu preparation. Eating at the table to be more present during food intake.
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3
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Habits and behaviors surrounding eating processes identified as health or risk factors, such as energy density, portion-size control, controlling emotional eating.
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4
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Beverages. Water versus sugar-sweetened drinks prepared at home or purchased at the store.
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5
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Preventing the risk of cardiovascular diseases by learning healthy eating habits and practicing these habits at home.
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6
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Integration. Practicing the skills learned during the intervention in each stage of preparing food and eating
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The intervention group did not cover physical activity topics.
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The key message was that healthy dietary habits and health risks are acquired at home and that opportunities for change can be identified in the processes that surround mealtimes. It begins with selecting and purchasing food, followed by preparation and consumption behaviors [19]. Mothers were encouraged to participate in the sessions which involved the use of food models, videos, slides, and, in some cases, real food. Upon completing each session, mothers were given printed material to add to a home consultation manual. Children in this group were not prescribed diets to reduce their body weight. Control group mothers and children (n=87) were given the usual nutritional consultation which consists of prescribed diets that covered their energy requirements according to their age and gender [14]. Similarly, control group mother/child pairs received information regarding food groups and portion sizes, were trained in the use of the food equivalence system to encourage variation and were instructed on how to prepare the diet at home. Neither group of children received physical activity programs. Upon concluding consultations and group sessions, mother/child pairs from both groups were asked to return for monthly follow-upsover the next three months.
The assignment to intervention or control groups was made using a block randomization with 8 mother/child pairs in each block to assure equal allocation to groups [20]. A study collaborator obtained a computer-generated randomization list using the Stata 11.0 program. Children were randomized at the end of the baseline examination. The calculation of the sample size was estimated using the formula of comparison of proportions in eating habits between the mothers/children dyad of the intervention and control groups [21, 22] to detect a 20% difference in eating habits, with significant level of 5% and 80% power; the size of sample required was 72 mother/children pairs per group and to allow for 20% drop-out during the follow-up, we aimed at recruiting 86 mother/children dyad per group.
Measurements at the beginning and end of the study
Anthropometry
The weight, height and waist circumference of children in both groups were measured according to international procedures. Weight was measured on a mechanical scale (Seca model-700, SECA Corp., Hamburg, Germany) with 50 g precision. Height was measured on a stadiometer (SECA model-225, SECA Corp., Hamburg, Germany) 0.1 cm precision. Meanwhile, waist circumference was measured at the end of an exhalation with non-elastic flexible tape (Seca model-200, SECA Corp., Hamburg, Germany) in a standing position at the midpoint between the lower costal border and the iliac crest. Body Mass Index (BMI) and percentile value were calculated using CDC data for reference [23], children with a BMI≥95 pc were categorized with obesity.
Blood pressure
Blood pressure was measured on children’s right arm with a mercury sphygmomanometer (ALPK2, Tokyo, Japan) using a cuff that suited arm length and perimeter and following 2004 National High Blood Pressure Education Program guidelines [24].
Questionnaires
A questionnaire of sociodemographic data was applied to the mothers at baseline. In addition, a survey of family feeding habits at home at baseline and three months was applied, the mother was asked about the child's breakfast habit, family feeding habits at the time of sitting at the table (place the salt shaker, sugar and sweetened soft drinks on the table, fill the plate, toask a food additional portion, force the child to finish the meal, accept the exchange of food to what the child wants), frequency of consumption of food (fried, roasted, fruits and vegetables) and drinks (simple water, sugary drinks prepared at home, natural juice, industrialized juice and soft drinks). The amounts of food consumption were not evaluated. A survey of physical activity and sedentary activities was applied [25]; no physical activity intervention was performed during this study.
Blood sample
5 mL venous blood samples after 12 h fasting periods were drawn to determine glucose (mg/dL) (hexokinase method Dimension RxL Max, Siemens Euro, DPC, Llanberis, UK), insulin (mIU/mL) (chemiluminescence IMMULITE 1000, Siemens), HDL cholesterol (mg/dl) (enzymatic reaction/catalase, using ADVIA ® 1800 equipment), and triglycerides (mg/dl) (ILAB 300, Instrumentation Laboratory, Barcelona Spain). Participating children’s HOMA-IR index was obtained through glucose and insulin data (IfxGf/22.5) [26].
Statistical analysis
Central tendency measures were used to describe the study population’s baseline characteristics. Student's t-test for independent samples was used to compare continuous variables with normal distribution or Mann-Whitney test no normal distribution, such as socio-demographic data, dietary habits, feeding behaviors, and biochemical and anthropometric data. Pearson X2 test was used to compare proportions between groups. The equal proportions test was used to assess the difference in proportions in dietary habits and behaviors between groups. Mixed effect linear regression models were used to evaluate the effect of the intervention on the variables of interest (BMI percentile, waist circumference, C-HDL, triglycerides, glucose, insulin and HOMA-IR) during follow-up. These models were adjusted for baseline data of the dependent variable, time, gender, baseline age and BMI percentile and maternal schooling. A model of mixed-effects linear regression was used to assess the interaction between the groups and the time of evaluation for the dependent variable HOMA-IR. Mean HOMA-IR by group (intervention or control) and by time was calculated and a graphic was done using marginal analysis. Statistical significance was considered at P<0.05. Analyses were carried out with STATA SE v.12.0 (Stata Corp, CollegeStation, TX, USA).