Nutrition and body composition as risk factors of non-communicable diseases in Saudi Arabia

Alkhalaf, Majid M. (2017) Nutrition and body composition as risk factors of non-communicable diseases in Saudi Arabia. PhD thesis, University of Glasgow.

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Background: Saudi Arabia is an affluent nation faced with steep population increase (~75% in just over 10 years) and a young population (63% aged under 30) in the context of globalized dietary habits and food supply leading to increase the trend of consumption junk food use. However, there are no national dietary surveys to give more accurate details. With existing high prevalence of obesity, it is foreseeable that Saudi Arabia (SA) will face a significant increase in the burden of non-communicable diseases (NCDs) in a short space of time. Reducing the behavioural and environmental risk factors associated with NCDs (physical activity, alcohol overuse, exposure to tobacco smoke, and low nutritionally balanced diet including high salt and energy intake and low intake of fruit and vegetables) requires cross-community sectors, including health, education, agriculture, and planning. Early detection and intervention also require reliable and cost effective tools. The relationship between chronic high salt intake and CVDs has already been established. This thesis examines the relationship between body composition and nutrition, and NCDs using techniques from the full breadth of Human Nutrition Research.
Methods: The first cross-sectional study focused on developing and validating a culture-specific FFQ for salt intake against 24-h urinary outputs and repeated 24-h dietary recall, to identify relationships between salt intake, socio-economic factors and blood pressure (BP); and explore dietary sources of salt intake.
In the second study, a secondary analysis of integrated data from five Saudi National Surveys assessed the performance of different anthropometric measures (body mass index (BMI), waist circumference (WC), waist to hip ratio (WHR) and waist to height ratio (WHtR)) and body composition indices (estimated skeletal muscle mass (SMM), the percentage of skeletal muscle mass to body weight (%SMM) and Skeletal Muscle Mass Index (SMI)) in predicting metabolic diseases. Saudi nationals only were included in the study. ROC analysis was used to explore the best predictor of metabolic diseases and develop new thresholds. To assess the agreement and misclassification of overweight and obesity using BMI and WC measurements, BMI in combination with WC measurements were used to classify participants as [High-Risk Adiposity by BMI and WC], [High-Risk Adiposity by BMI only], and [High Risk Adiposity by WC only] based on the action levels. Each anthropometric and muscle mass indices were categorised to deciles. Additionally calculated were age-adjusted odds ratios by applying logistic regression models of the different metabolic risk factors in case of an increase of one decile of the respective anthropometric and estimated SMM parameter.
In the third study, a cross-sectional survey was developed using the Theory of Planned Behaviour to provide a holistic understanding of factors that may influence food choices and behaviours, and in particular, intentions of adopting a nutritionally-balanced diet. External variables including age, gender, socio-economic status, and being aware of health and nutrition policies and others were included into the model as they were potentially related to TPB constructs. Attitude toward behaviour, subjective norms, perceived behavioural control and knowledge as actual barriers to behaviour were assessed.
Results: In the first study, the newly developed Saudi FFQ was found to be of moderate validity in ranking people based on their estimated salt intake, and performed as well as other salt FFQ developed for other nations. The Riyadh population used in this survey consumed 8.7 g salt per day (estimate), higher than the recommended level of salt (>5 g/d for salt). A minority (18%) met the recommended level. The main sources of salt were, surprisingly, vegetables and un-processed foods, and a positive relationship between income and salt intake was observed. Meanwhile, salt intake, defined by FFQ, was associated with systolic BP only (R=0.089, p=0.036), an association which disappeared when adjusted for age, WC and gender.
The second study highlighted that a majority of Saudi adults could be categorized as overweight or obese (72%). Worryingly, short of half of those with a normal BMI (18.5–25) aged over 45 also had a large waist. Combining WC and BMI did not improve their value as predictors of metabolic diseases and WC was the best overall predictor of metabolic diseases while BMI was the poorest. This study suggests new cut-off points for WC in SA, in a context of metabolic diseases, ranging between 90 to 92 cm (women) and 94 to 99 cm (men). The newly developed WC cut-offs are higher than the cut-offs for Asian men and women (90 and 80 cm, respectively). The new WC cut-off for women is higher than the cut-off for Caucasian women (88 cm); and the WC cut-off for men is lower than the cut-offs for Caucasian men (102 cm).
The obesity prevalence based on BMI and WC also increased proportionately with both SMM (kg) and SMI (kg/m2) increase while the obesity decreased proportionately with %SMM increase. SMI was a poor predictor of metabolic diseases while %SMM was the best, having the highest AUC levels. New (defined) cut-off points for %SMM for metabolic diseases were defined, ranging from 29 to 32% for men and 26 to 28% for women.
The third study highlighted that very few SA adults have been exposed to national nutrition and health guidelines (18%). Awareness of these was the strongest predictor of attitude toward behaviour, social norms and knowledge of nutritionally-balanced diet whilst perceived social pressure to engage in behaviour toward a more nutritionally balanced diet (SN) was the strongest predictor of subjects’ intention.
Conclusion: Study 1 added a new and unexpected source of salt intake including vegetables and unprocessed foods. These findings raise a concern regarding the encouragement to increase intake of vegetables without including advice regarding cooking advice, in light of the risk of higher salt intake in SA. It would be worthwhile to consider education strategies towards the use of alternative ingredients or dressings in salad and cooked vegetables.
Study 2 added an evidence about the weakness of BMI and SMI in predicting metabolic diseases and misclassifying the population. The study suggests using WC and %SMM as alternative measures and adopting the newly developed cut-offs.
Study 3 sheds the light on possible avenues for policies, health promotions and nutrition interventions to focus on Saudi adults, in order motivate the population to adopt nutritionally balanced diet by increasing population knowledge and awareness.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Non-communicable diseases, body composition, nutrition, salt, food frequency questionnaire, obesity, muscle mass, balanced diet.
Subjects: R Medicine > R Medicine (General)
Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Medicine, Dentistry & Nursing
Supervisor's Name: Combet, Dr. Emilie and Edwards, Prof. Christine and Lean, Prof. Michael
Date of Award: 2017
Depositing User: Dr. Majid Alkhalaf
Unique ID: glathesis:2017-8533
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 25 Oct 2017 08:02
Last Modified: 08 Apr 2022 17:14
Thesis DOI: 10.5525/gla.thesis.8533

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