Structural equation model

A structural equation model was constructed using SmartPLS. The single endogenous latent variable was “Anthropometric measurements” (a combination of BMI, body fat, and waist to hip ratio). The path coefficients representing the partial correlations between the anthropometric measurements and three exogenous variables were computed for (a) “Unhealthy diet and lifestyle” (a combination of smoking, consumption of alcohol, sodium, chloride, sugars, and saturated fatty acids); (b) “Healthy diet and lifestyle” (a combination of consumption of dietary fibre, fruit and vegetables, and physical activity); and (c) “Blood measurements” (a combination

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of blood glucose, blood pressure, and LDL-cholesterol). The path diagram output by the graphic user interface of SmartPLS is presented in Figure 3.11.

Figure 3.11 PLS-SEM path diagram of relationships between anthropometric and blood measurements, health and lifestyle

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The PLS-SEM model explained almost half of the variance (R2 = 48.9%) in the anthropometric measurements. Using the criteria of Ferguson (2009) this R2 (between 25% and 64%) represented a “moderate” effect size. The path coefficients indicated that the anthropometric measurements were correlated with both the blood measurements and the diet and lifestyle factors. The unhealthy diet and lifestyle factors were the most strongly correlated with anthropometric measurements, indicated by the largest path coefficient (β = 0.529). The positive coefficient indicated that the anthropometric measurements would increase if the student was a smoker and consumed large amounts of alcohol, saturated fatty acids, salt, and sugars. The blood measurements were less strongly correlated with the anthropometric measurements, indicated by the smaller path coefficient (β = 0.310). This positive coefficient predicted that the anthropometric measurements would be greater if the student had high levels of blood pressure, blood glucose, and LDL-cholesterol.

The healthy diet and lifestyle factors were the least strongly correlated with the anthropometric measurements, indicated by the smallest path coefficient (β = -.213). This negative coefficient predicted that the anthropometric measurements would be smaller if the student consumed high amounts of dietary fibre, consumed at least five servings of fruit and vegetables per day, and also had very active levels of physical activity.

103 3.12 Discussion

The results of the second survey, based on a convenience sample of 40 students addressed Research Question 1: What are the dietary and lifestyle risk factors for cardiovascular disease among university students in Edinburgh, Scotland. Several CVD risk factors were identified, including obesity, hypertension, unhealthy diet, low physical activity, and smoking tobacco. No symptoms of hyperlipidemia or diabetes were identified.

3.12.1 Obesity

According to the World Health Organisation (2012a), one in ten adults in the world is obese (defined as having a BMI > 30 kg/m2_{). The number of overweight and} obese children and adolescents has doubled in the last two decades in the Western world (Ogden et al. 2002; 2010). Only 5% of the students sampled in the current study were, however, classified as obese, implying that the study sample may not have been representative. There may be a higher level of obesity in the entire undergraduate population.

3.12.2 Hypertension

According to the British Hypertension Society, the prevalence of hypertension in people over 16 years old in UK is 31.5% in men and 29.0% in women. Only 2.5% of the students sampled in the current study had symptoms of hypertension (i.e., systolic blood pressure ≥ 140 mm Hg and/or diastolic blood pressure ≥ 90 mm Hg.) implying that the study sample may not have been representative. There may be a higher level of hypertension in the entire undergraduate population.

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On average, the participants consumed substantially more saturated fatty acid, sodium, chloride than listed in the dietary reference intakes (DRI) for males and females aged 19-30. Excessive consumption of saturated fats reflects a diet rich in animal sources, including beef, lamb, pork, lard, cream, cheese, and other dairy products. In addition, it may reflect consumption of many baked goods and fried foods. Excessive consumption of saturated fatty acid is known to be a risk factor for CVD in the UK, and therefore its consumption should be reduced (British Dietetic Association, 2012; British Heart Foundation, 2015). The results confirmed the assertion of the National Health Service (2012) that “Most people in the UK eat too much saturated fat”.

The average consumption of sodium was in excess of the DRI values. Excessive consumption of sodium reflects a high intake of salt. Many studies have linked dietary salt intake to hypertension, and a reduction in dietary salt intake has been reported to lower blood pressure (Frisoli et al. 2012).

The average consumption of dietary fibre was substantially less than the DRI values. The relatively low consumption of dietary fibre was an important finding, because dietary fibre may have a protective effect on the risk of CVD (Bazzano et al. 2003). The relatively low consumption of polyunsaturated fats was another important finding, because they provide essential fatty acids and fat-soluble vitamins (Crawford, 2013).

The consumption of non-milk extrinsic sugars, found in foods such as sweets, biscuits, cakes, pastries, breakfast cereals, and beverages such as soft drinks, may be a risk factor for CVD (Young et al. 2014). The relatively low consumption of non-milk extrinsic sugars (lower than the DRI values) observed among the students at Heriot Watt University reflected a reduced risk of CVD, and contradicted previous studies suggesting

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that the mean intake of extrinsic sugars in UK was significantly higher than the UK recommended population average (Rugg-Gunn et al., 2007; McNeill et al. 2010).