3.3. Data collection
Two forms were used to collect data. The first was the Anthropometric Measurement Form, which includes the child’s age, gender, measurement date, bodyweight, and height. Two digital bascules certified for European conformity (EC) were used to measure the weight and height of the children. The brand of the digital weight scales was NAN, and they were medical scales with stadiometers. Their calibration was checked. The first form was filled out by the data-collection team.
The second survey form contained 25 questions regarding the parents’ education level, job, weight and height, and the child’s name, school name, age, gender, birth weight, nutrition during infancy, means of travel to school, distance to school, having breakfast, computer usage, watching television, and regular physical activities. A list of the foods consumed by children was prepared to examine their eating habits, and parents were asked how many times a week the children consumed these foods. The food list included high-calorie foods and beverages such as honey, jam, chocolate, potato/corn chips, and coke; dried fruits such as hazelnuts and peanuts; fruits, meat, and dairy products. Consumption rates were classified and analyzed as three times or less a week and four times or more a week. The child would give the parents the form, and they would complete it. The child’s birth weight and parents’ weights and heights were self-reported. The parents’ BMIs were calculated by researchers according to their weight, height, and gender.
Data collection was conducted in schools between October 2012 and January 2013. The anthropometric measurements on the first form were filled out by the data-collection team in the schools’ classrooms. Two teams made the measurements. These were five-person teams, including two researchers and three pollsters. Before the measurements, the teams were taught how to take the measurements and fill out the forms. This training lasted 40 minutes long. For their measurements, the children wore t-shirts or shirts and pants or skirts. Bodyweight and height were measured without shoes. A screen was used to protect the children’s privacy.
When the child was measured, he/she was given an envelope and asked to give it to his/her parents. The envelope contained a note regarding the research, an informed consent, and a survey form. The families of the children who agreed to participate in the research were asked to fill out the informed consent and survey form, place them back in the envelope, and return it to us. The form was sent to 3,028 families, and 1,813 families returned them in completed form. The family response rate was 60%.
3.4. Data Analysis
Data were analyzed using the statistical package for the social sciences (SPSS) 21 program. Each child’s body index was calculated by instructions for excel body-mass index (BMI) Calculator, a program developed by the centers for disease control and prevention (
20). First, the child’s gender, bodyweight, height, date of birth and date of measurement were entered into the program, and then the BMI was calculated. Overweight was accepted as a BMI at or above the 85th percentile and below the 95th percentile for children of the same age and sex. Obesity is accepted as a BMI at or above the 95th percentile for children of the same age and sex (
2). The data were analyzed by frequency and logistic regression in SPSS and Excel. In this research, the child’s gender, age, socioeconomic status, student transport, distance to school, dietary habits (having breakfast, consuming milk puddings, eating nuts, and milk chocolate), birth weight, parents’ body-mass index, and parents’ education level, were included in the analysis for logistic regression. Significance according to the chi-square test was the criterion applied in choosing variables. Then, the data were considered as independent variables in the group comparisons of overweight and normal weight/underweight. Inverse logistic regression analysis was used to examine whether these variables were a risk factor, while the inclusion/exclusion criteria for the model were agreed to be 0.01 and 0.05, respectively. Reference data for logistic regression were constructed as follows.
For obesity:
Dependent variables were coded as obese (1), normal and underweight (0), and overweight were removed from the database.
Independent variables were coded as follows:
Gender: female (0), male (1)
Socio-economic status: lower SES (0), moderate SES (1), higher SES (2)
Traveling to school: on foot (0), by car or bus (1)
Birth weight: 2500 to 4000 grams (0,) < 2500 grams (1), > 4000 grams (2)
Mother’s and father’s education: elementary school (0), high school (1), university (2)
Mother’s and father’s BMIs: underweight (0), normal (0), overweight or obese (1)
Consumption of milk chocolate/ milk pudding/meat/nuts: less than 3 times per week (0), 4 or more times per week (1)
For being overweight:
Dependent variables were coded as overweight (1), normal and underweight (0), and obese were removed from the database.
Independent variables were coded as follows:
Age: under 10 years (0), 11 to 15 years (1)
Distance from home to school: less than 1 kilometer (0), between 1 and 2 kilometers (1), between 3 and 4 kilometers (3), between 5 and 6 kilometers (4), 6 kilometers or more (5)
Having breakfast: no (0), yes (1)
Gender: female (0), male (1)
Socio-economic status: lower SES (0), moderate SES (1), higher SES (2)
Traveling to school: on foot (0), by car or bus (1)
Mother’s and father’s education: elementary school (0), high school (1), university (2)
Mother’s and father’s BMI: underweight (0), normal (0), overweight or obese (1)
Consumption of nuts: less than 3 times per week (0), 4 or more times per week (1)