Height and Weight protocol

Students’ height and weight were only measured by the researcher using validated international standardised protocol (See below).

4.10.1 Height and Weight issues

1. Height and weight are used to calculate Ideal Body Weight (IBW) and Body Mass Index (BMI).

2. An inaccurate height and weight results in an inaccurate IBW and BMI 3. The same scale was used for all students. After students completed the

questionnaire, their height and weight were measured and recorded.

4.10.2 Obtaining Height measurement

1. Make sure the student on the middle of the firm surface.

2. Students will be measured in the standing position using portable stadiometer. 3. Clothing should be minimal when measuring height so that posture of the

students can clearly be seen.

4. Students will be asked to remove shoes AND socks (thick socks can make a difference) and any heavy clothes and to stand with heels together, arms by their sides and eyes looking straight ahead.

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5. Students should stand with the back and head straight so that the Frankfurt plane is horizontal and the eyes are focused forward (see Figure 4.1). Back of the heels, buttocks, shoulder blades and back of the head. However if the participant is overweight it may only be possible to obtain contact at the buttocks and shoulder blades as it is important for the participant to stand straight.

6. Feet, knees, buttocks and shoulder blades should be in contact with the vertical surface of the stadiometer.

7. Arms should be hanging loosely at the sides with palms facing the thighs; the head is not necessarily in contact with the wall.

8. Students will be asked to take a deep breath and stand tall to aid in straightening of the spine. Shoulders should be relaxed.

9. The moveable headboard should be gently lowered until it touches the crown of the head.

10. Record the measurement to the nearest 0.1cm on the back of the last page of the student Questionnaire.

Figure 4-1: Height Measurement.

4.10.3 Obtaining Weight measurements 1. Ensure balance is on a firm, flat surface.

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3. The student will be asked to remove heavy outer clothing (such as coats, jackets, and vests), purses, shoes, and any heavy accessories such as belts with heavy belt buckles. The student should also remove everything from their pockets including money (coins), pens, pencils, wallets, and papers.

4. Students stand on the centre of scales, without support and with their weight distributed evenly on both feet with feet close together, arms at sides and eyes looking forwards, record body mass to nearest 0.1 kg.

5. Make sure the scale is zero-balanced before each student is weighed.

6. It is strictly important not to react to the student’s weight. While the weight measurement is being taken, it is important not to be judgmental. Any communication about the weight should be neutral (neither positive nor negative) and professional.

4.10.4 Calculating BMI

Student’s weight and height were measured and body mass index was calculated. Body Mass Index (BMI) is a simple index of weight-for-height that is commonly used to classify underweight, overweight and obesity. It is defined as the weight in kilograms divided by the square of the height in metres (kg/m2). Anthropometry, based on weight and height measures, is one of the methods used most frequently to identify people at higher risk of overweight and obesity, and body mass index (BMI) is the index used most often.

Cole et al. Proposed BMI cut-off values for children and adolescents (Cole et al., 2000). The use of Cole et al. Criteria (BMI cut-off values) is widely accepted and used (Fletcher et al., 2004, Andersen et al., 2005). However, It has been reported that Cole et al. Values have a low sensitivity when compared with weight-for height, which makes their use to screen obesity in children less useful since they could not detect more than 80% of those classified as obese by WHO (Abrantes et al., 2003). Also, it has been found that the sensitivity, specificity and agreement of BMI values proposed by Cole et al. With weight-for-height index are better for pre-school children than for schoolchildren (Abrantes et al., 2003). However, the ideal gold standard method to diagnose overweight and obesity is a more direct measure of body fat such as dual-energy X-ray absorptiometry (DEXA), which is clearly more

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difficult to obtain (Abrantes et al., 2003). In my study BMI cut off for adults was used, but only for the chi-square test to investigate overweight differences among group (BMI was used as a continuous variable in linear regression analyses). First because the majority (45%) of the participants were aged 18 or older, and BMI cut-offs of 25 and 30 are used to classify individuals as overweight and obese for this age, respectively, whereas the remaining students were 15 years old (3.4%), 16 years old (20.1%) and 17 years old (30.7%). However, the average BMI cut off for adolescents between 15-17 years old (based on Cole et al., criteria) is 24%, and it was presumed that it will not affect the results.

4.11 Data collection

Data collection was by means of a self-completion questionnaire, completed in a class setting and administered by the researcher. The questionnaire aims and objectives were explained for students to encourage them to participate in this study. The questionnaires were distributed in classes and collected by the researcher during class session which is about 45 minutes. Confidentiality was of utmost importance and a procedure that ensures pupils’ anonymity. The confidentiality issues and process were explained to students and taken in account by the researcher to enhance authenticity of the student responds. The project questionnaire is based on Health Behaviour in School-aged Children survey (HBSC), Global school-based student health survey (GSHS) and Youth Risk behaviours Surveillance (YRBS), surveys among school-aged children and adolescents carried in many European countries and Youth Risk Behaviour Surveillance (YRBS) in United States.