BACKGROUND: Type 2 diabetes and cardiovascular disease (CVD) are among the leading causes of death in the United States. The Metabolic Syndrome, which comprises a cluster of cardiometabolic risk factors, puts individuals at increased risk for these diseases. It is therefore important that people with Metabolic Syndrome, at high risk for CVD and type 2 diabetes, are identified and treated. Since it may not often be practical to obtain the laboratory measures necessary for diagnosing the Metabolic Syndrome, simple anthropometric measures are a useful way of quickly identifying individuals at increased risk for the Metabolic Syndrome. OBJECTIVE: The purpose of this thesis is to evaluate the utility of three of the most commonly used anthropometric measures – Body Mass Index (BMI), Waist Circumference (WC), and Waist-to-Height Ratio (WC) – for classifying individuals with and without the Metabolic Syndrome and its component risk factors in the United States. Using Receiver Operating Characteristic (ROC) curve analysis and Area Under the Curve (AUC) statistics, this thesis will assess the utility of each body measurement and compare it to BMI. METHODS: A large, multi-ethnic, nationally representative sample from the National Health and Nutrition Examination Survey (NHANES) 2007-2010 was used for this analysis. The study sample was restricted to adults aged 20-65 with complete information on height, weight, waist circumference, blood pressure, HDL cholesterol, fasting glucose, and triglycerides (n=3,769). In order to compare the utility of different anthropometric measures for classification, weighted ROC curves were constructed for each anthropometric measure-outcome combination and AUC statistics were compared. AUC statistics were calculated by approximating the definite integral of the ROC curves with the trapezoidal rule. Variances for AUC statistics and differences in AUC statistics were estimated with jackknife repeated replication. Analyses were completed for the entire sample and separately for non-Hispanic whites, non-Hispanic blacks, and Mexican Americans. RESULTS: For the entire sample, WC (AUC=0.752) did a better job than BMI (AUC=0.728) at classifying individuals with and without the Metabolic Syndrome (p CONCLUSION: Waist circumference should be considered, especially over BMI, for risk stratification in clinical settings and research. Further research should attempt to identify optimum waist circumference cut points for use in the US population.

The human body best performs when it is physically active. The consequences of inactivity can bring about many health risks. The purpose of this study was to investigate the relationship between physical activity, waist circumference and medication use among South African men. Men between ages 30 and 65 years (N = 5000, ͞x = 43.2; ± 8.55) were included in this study. With the use of medication, distinction was drawn between various ethnic groups. Subjects selected for this study are members of the same medical aid. The respondents that formed part of a non-random availability population and participated voluntarily were used in this study. According to the results, it appears that out of a total of 4 954 respondents, 58.3% had the lowest incidence of physical activity, 21% were moderately active and 20.7% highly active. WC appears much higher among those that fall within the lowest incidence of physical activity group. No significant difference was observed between moderately and highly active people. There are 11 members in the high Physically Active (PA) category that has the highest WC (X =131.5). When scrutinising the different ethnic groups it is obvious that moderate to high PA is associated with a lower WC. Chronic medication (CM) use is determined on the basis of the registry for chronic medication use of the relevant medical aid. Those who participated in the assessment of waist circumference, CM and PA consisted of 4 964 respondents. In this study distinction was drawn between three medical condition influenced by exercise, namely diabetes, cholesterol and depression and hypertension. The results indicate that CM use is associated with higher WC and reduced kCal consumption. The majority of respondents (78%) do not use medication and 21.9% do. Those that do not use medication showed to have the lowest WC. However, respondents that are highly active and also use CM showed a lower MO than those that are low and moderately active. It can thus be deduced that regular physical activity is directly related to one’s health. / Thesis (MSc (Biokinetics))--North-West University, Potchefstroom Campus, 2013.

The human body best performs when it is physically active. The consequences of inactivity can bring about many health risks. The purpose of this study was to investigate the relationship between physical activity, waist circumference and medication use among South African men. Men between ages 30 and 65 years (N = 5000, ͞x = 43.2; ± 8.55) were included in this study. With the use of medication, distinction was drawn between various ethnic groups. Subjects selected for this study are members of the same medical aid. The respondents that formed part of a non-random availability population and participated voluntarily were used in this study. According to the results, it appears that out of a total of 4 954 respondents, 58.3% had the lowest incidence of physical activity, 21% were moderately active and 20.7% highly active. WC appears much higher among those that fall within the lowest incidence of physical activity group. No significant difference was observed between moderately and highly active people. There are 11 members in the high Physically Active (PA) category that has the highest WC (X =131.5). When scrutinising the different ethnic groups it is obvious that moderate to high PA is associated with a lower WC. Chronic medication (CM) use is determined on the basis of the registry for chronic medication use of the relevant medical aid. Those who participated in the assessment of waist circumference, CM and PA consisted of 4 964 respondents. In this study distinction was drawn between three medical condition influenced by exercise, namely diabetes, cholesterol and depression and hypertension. The results indicate that CM use is associated with higher WC and reduced kCal consumption. The majority of respondents (78%) do not use medication and 21.9% do. Those that do not use medication showed to have the lowest WC. However, respondents that are highly active and also use CM showed a lower MO than those that are low and moderately active. It can thus be deduced that regular physical activity is directly related to one’s health. / Thesis (MSc (Biokinetics))--North-West University, Potchefstroom Campus, 2013.

Motivation: Abdominal obesity (hereafter referred to as "obesity") is becoming the biggest "global epidemic" of our modern times. It is associated with a range of diseases, including cardiovascular diseases and hypertension. Recent research showed that an increase in sympathetic activity is of central importance in the pathogenesis of obesity-related diseases. Increased leptin levels and impaired baroreflex sensitivity have both been independently associated with abdominal obesity and increased sympathetic activity. A perception of poorer health may also contribute to the physiological characteristics of obesity-related diseases. A lack of data regarding sympathetic activity, leptin levels, baroreflex sensitivity and perception of health in Africans, serves as a motivation for conducting this study. Objective: To investigate the contributions of leptin levels, baroreflex sensitivity and perception of health data to increased sympathetic activity in lean and obese African women from South Africa. Methodology: The manuscript presented in Chapter 2 made use of the data obtained in the POWIRS (Profiles of Obese Women with the Insulin Resistance Syndrome) study. A group of 102 urbanized African women, living in the North-West Province of South Africa, was recruited according to body mass indexes. Only 85 subjects were included for analysis due to incomplete datasets. For this study, subjects were divided into lean and obese groups according to their waist circumferences. Anthropometric measurements were done according to standardized methods. Resting cardiovascular measurements were obtained from Finometer observations. Resting, fasting levels of leptin were calculated after radioimmunoassay analyses. Subjective perception of health was determined by means of the 28-item General Health Questionnaire. Comparisons between the groups were done using analysis of covariance (ANCOVA) whilst adjusting for cardiovascular risk factors (age. smoking, alcohol consumption and physical activity). Correlation coefficients were determined to indicate any associations between leptin, baroreflex sensitivity and perception of health with sympathetic activity (represented by heart rate) and other cardiovascular variables. The study was approved by the Ethics committee of the North-West University and all the subjects gave informed consent in writing. The reader is referred to the Methods section in Chapter 2 for a more detailed description of the subjects, study design and analytical procedures used in this dissertation. Results and conclusion: Results from this study indicate that obese African women, compared to lean African women, were older, reported higher physical activity, and exhibited higher diastolic and mean blood pressure, heart rate, cardiac output, arterial compliance, leptin and hypertension prevalence rate values. In lean African women social dysfunction was positively associated with diastolic and mean blood pressure and arterial resistance, and negatively with arterial compliance. In obese African women baroreflex sensitivity was negatively associated with diastolic blood pressure, which could be an indication of impaired baroreflex sensitivity. In this obese group a perception of social dysfunction was associated with decreased heart rate. Although leptin and heart rate were significantly higher in the obese Africans, no significant correlations existed between these variables to reflect leptin's enhancement of sympathetic activity. However, leptin correlated weakly but positively with cardiac output (p = 0.054, r = 0.32). In conclusion, baroreflex sensitivity (although similar between groups) and leptin seem to contribute to blood pressure and thus hypertension in obese African women, possibly through increased sympathetic activity and volume loading. A perception of poorer health, especially a perception of social dysfunction, could possibly contribute to this image. / Thesis (M.Sc. (Physiology))--North-West University, Potchefstroom Campus, 2007.

Thesis (Ph.D. (Human Movement Science))--North-West University, Potchefstroom Campus, 2010.

Adiposity has been linked to impaired respiratory function in adults but whether the distribution of adipose tissue has a differential effect on pulmonary function is still uncertain. Moreover, in children, the relationship between adiposity and lung dysfunction is not clearly understood. A two-stage multivariate analysis was conducted using data from 5604 Canadians aged 6 to 79 years who participated in the Canadian Health Measures Survey (CHMS). The associations of various anthropometric and skinfold measures with lung function were examined separately in adults and children. After adjustment of covariates, waist circumference and subscapular skinfold thickness showed the strongest inverse associations with FVC and FEV1 in men. In women, BMI and sum of five skinfolds had the largest impact on pulmonary function. FVC and FEV1 in boys were most affected by waist-to-hip ratio and triceps skinfold. In girls, adiposity was not linked to the lung function testing variables. Adiposity measures have differing effects on respiratory function depending on age and sex group.

60 % of Canadians have suboptimal vitamin D (<75 nmol/L) and 25% are obese. Obesity has been reported to be a risk factor for low vitamin D, but there is uncertainty about the magnitude of the association. Linear regression was performed using data from the nationally representative cross-sectional Canadian Health Measures Survey (2007-2009). Height, weight, waist circumference (WC), and vitamin D levels were directly measured. There were 5298 participants aged 6 to 79 years. Using a conservative p value of 0.001, body mass index (BMI) category obese / obese I was positively associated and WC was inversely associated with vitamin D level in crude analysis. WC was inversely associated with vitamin D level in multivariate analysis. The pattern of relationship is not the same as other studies, yet this was a large study with direct measurements. There may be issues with linearity of relationships or subgroups disturbing the relationship.

Thesis (Ph.D. (Human Movement Science))--North-West University, Potchefstroom Campus, 2010.

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / Background & aims: Several studies have examined the effect of vegetarian diets (VD) on metabolic syndrome (MetS) or its components, but findings have been inconsistent. The aim of this study was to perform a systematic review and meta-analysis of randomized controlled trials (RCTs) and observational studies to assess the association between VD and MetS or its components (systolic blood pressure [SBP], diastolic blood pressure [DBP], fasting glucose triglycerides, waist circumference [WC], HDL-cholesterol (HDL-C)) in adults. Methods: The Cochrane Library, EMBASE, PubMed, Web of Science, and Scopus were searched. RCTs, cohort studies and cross-sectional studies evaluating the effects of VD on MetS or its components in adults, with omnivore diet as control group, were included. Random effects meta-analyses stratified by study design were employed to calculate pooled estimates. Results: A total of 71 studies (n = 103 008) met the inclusion criteria (6 RCTs, 2 cohorts, 63 cross-sectional). VD were not associated with MetS in comparison to omnivorous diet (OR 0.96, 95% CI 0.50–1.85, p = 0.9) according to meta-analysis of five cross-sectional studies. Likewise, meta-analysis of RCTs and cohort studies indicated that consumption of VD were not associated with MetS components. Meta-analysis of cross-sectional studies demonstrated that VD were significantly associated with lower levels of SBP (mean difference [MD] −4.18 mmHg, 95%CI −5.57 to −2.80, p < 0.00001), DBP (MD −3.03 mmHg, 95% CI −4.93 to −1.13, p = 0.002), fasting glucose (MD −0.26 mmol/L, 95% CI −0.35to −0.17, p < 0.00001), WC (MD −1.63 cm, 95% CI −3.13 to −0.13, p = 0.03), and HDL-C (MD −0.05 mmol/L, 95% CI −0.07 to −0.03, p < 0.0001) in comparison to omnivorous diet. Heterogeneity of effects among cross-sectional studies was high. About, one-half of the included studies had high risk of bias. Conclusions: VD in comparison with omnivorous diet is not associated with a lower risk of MetS based on results of meta-analysis of cross-sectional studies. The association between VD and lower levels of SBP, DBP, HDL-C, and fasting glucose is uncertain due to high heterogeneity across the cross-sectional studies. Larger and controlled studies are needed to evaluate the association between VD and MetS and its components. / Revisión por pares

BACKGROUND & AIMS - Metabolic syndrome (MetS), characterized by abdominal obesity, atherogenic dyslipidemia, elevated blood pressure, and insulin resistance is a major public health concern in the United States. The effect of Apolipoprotein E (Apo E) polymorphism has been relatively well studied in relation to cardiovascular disease; however, its effects on MetS are not well established. METHODS - We conducted a cross-sectional study consisting of 1,551 participants from the National Heart, Lung, and Blood Institute (NHLBI) Family Heart Study to assess the relation of Apo E polymorphism with the prevalence of MetS. Information on the different Apo E genotypes was extracted from the database and we defined MetS according to the AHA-NHLBI-IDF-WHO Harmonized Criteria. We used generalized estimating equations to estimate adjusted odds ratios for prevalent MetS and the Bonferroni correction to account for multiple testing in the secondary analysis. RESULTS – Our study population had a mean age (SD) of 56.5 (11.0) years and 49.7% had MetS. There was no association between the Apo E genotypes and MetS. The multivariable adjusted ORs (95% CI) were 1.00 (reference), 1.26 (0.31-5.21), 0.89 (0.62- 1.29), 1.13 (0.61-2.10), 1.13 (0.88-1.47) and 1.87 (0.91-3.85) for the *e3/e3, *e2/e2, *e2/e3, *e2/e4, *e3/e4 and *e4/e4 genotype respectively. In a secondary analysis, the *e2/e3 genotype was associated with lower HDL levels, with the multivariable adjusted ORs (95% CI) of 0.59 (0.36-0.95) when compared to the reference *e3/e3 genotype. CONCLUSIONS - Our findings do not support an association between Apo E polymorphism and MetS in a multi-center population based study of predominantly white US men and women. The *e2/e3 genotype was associated with lower HDL levels as compared to the *e3/e3 genotype. KEY WORDS: Apolipoprotein E (Apo E) polymorphism, metabolic syndrome, blood pressure, glucose, waist circumference, triglycerides, high-density lipoprotein cholesterol