The increasing prevalence of abdominal obesity worldwide poses a serious public health problem and hence, presents a target for research designed to improve the assessment or treatment of abdominal obesity. Specifically, the first study in this thesis investigated the influence of age and gender on visceral (VAT) and abdominal subcutaneous adipose tissue (ASAT) for a given waist circumference (WC) in 481 men and women varying widely in age and BMI. Significant gender differences in VAT and ASAT for a given WC were observed, however, only the relationship between WC and VAT was substantially influenced by age. The second study examined whether the associations between VAT, ASAT and the metabolic syndrome (MetS) were altered depending on measurement methodology used to assess VAT and ASAT. The odds ratio (OR) for MetS was higher for total VAT volume (OR=7.26) and the partial volumes at T12-L1 (OR=7.46) and L1-L2 (OR=8.77) compared to the classic L4-L5 (OR=3.94) measurement. The OR for MetS was not substantially different among the ASAT measures (OR~2.6). Measurement site for VAT, but not ASAT, has a substantial influence on the magnitude of the association with MetS. The third study examined the independent associations between VAT, ASAT, liver fat and all-cause mortality in 291 men (97 decedents and 194 controls, mortality follow-up of 2.2±1.3 years). In a model including VAT, ASAT, liver fat, age, and length of follow-up, only VAT (1.93 [1.15-3.23]) remained a significant predictor of mortality. We concluded that VAT is a strong, independent predictor of all-cause mortality in men. The purpose of the final study was to determine the effect of aerobic exercise dose (energy expenditure) on WC in sedentary, overweight/obese postmenopausal women (n=424). The women were randomly assigned to a control group or one of three aerobic exercise groups that exercised at energy expenditures of 4-, 8-, or 12-kcal/kg body weight/week. By comparison to control, there were significant reductions in WC in the exercise groups (~3 cm, P <0.05), which were independent of weight loss. However, the amount of exercise performed was not associated with reductions in WC in a dose dependent manner. / Thesis (Ph.D, Kinesiology & Health Studies) -- Queen's University, 2007-05-17 19:24:06.777

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.

Objectives: The aim of this study was to determine the prevalence of MetS among different African populations using the new Joint Statement Criteria. Hereafter we aimed to determine whether waist or neck circumference is the best predictor of MetS risk after ethnic, gender and age-specific cut-points were developed. Lastly, we aimed to determine whether afore-mentioned cut-point can predict albumin:creatinine ratio as a marker of target organ damage. Methods: The study sample (N=409) comprised of urban African (men, N=101; women, N=99) and Caucasian (men, N=101; women, N=108) teachers from the Dr. Kenneth Kaunda Education district in the North-West Province, South Africa. Participants were aged between 25 and 65 years. Anthropometric measurements, albumin:creatinine ratio and other markers of the metabolic syndrome (MetS) (systolic and diastolic blood pressure [SBP and DBP], glucose, triglycerides [TG] and high density lipoprotein [HDL]) were determined. Results: Africans (65 and 63 % for men and women) and Caucasian men (73%) showed high prevalence of MetS; ROC analysis determined neck circumference (NC) cut-points of 39 and 35 cm for young and older African men, 32 and 35 cm for young and older African women, 40 and 41 cm for Caucasian men and 34 and 33 cm for Caucasian women. This NC cut-point can be used to determine metabolic syndrome risk in all groups, except in African women; ROC developed waist circumference (WC) cut-points were 91 cm for all African male groups, 84, 81 and 84 cm for young, older and total group of African women. Suggested WC cut-points for Caucasian men were 93 cm for the young group and 97 cm for older as well as total Caucasian male groups, while cut-points for Caucasian women were 87 cm, 79 cm and 84 cm for young, older and total Caucasian women. These WC cut-points were good measures of metabolic syndrome risk in all groups; neither cut-point of WC nor NC could increase the risk of albumin:creatinine ratio. Conclusion: African women as a group present with few MetS risk factors and glucose is associated with renal function risk in Africans; NC cut-points may be used as an additional anthropometric marker to predict the metabolic syndrome in a South African cohort, but not in African women; WC cutpoints demonstrated to be good predictors of the metabolic syndrome in the same South African cohort, especially among men; WC would seem to be the best measure of MetS risk in all African populations, although NC can also be used for this purpose in all African populations, except in African women. / Thesis (PhD (Human Movement Science))--North-West University, Potchefstroom Campus, 2012