Masters Degrees (Exercise, Sport and Lifestyle Medicine)

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Browsing Masters Degrees (Exercise, Sport and Lifestyle Medicine) by browse.metadata.advisor "Dickie, Kasha Elizabeth"

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    Glucose control, cardiorespiratory fitness, and dietary composition in healthy men.
    (Stellenbosch : Stellenbosch University, 2020-12) Moller, Johanna Christina; Terblanche, Elmarie; Dickie, Kasha Elizabeth; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Sport Science.
    ENGLISH ABSTRACT: The prevalence and incidence of type 2 diabetes mellitus (T2DM) is worrisome and places a great burden on health care systems worldwide, while negatively affecting the quality of life of countless individuals. Continuous glucose monitoring (CGM) has not only improved the quality of diabetes care, but has also identified differences in the glucose profiles of individuals with otherwise seemingly healthy glucose control. The question arises whether CGM and the measurement of glycaemic variability would be more sensitive in identifying individuals who are at risk for imminent insulin resistance and subsequent T2DM. It may have significant clinical value if it can be determined if free-living glycaemic variability is closer related to lifestyle factors, such as diet and exercise, than the traditional measures of glucose control. Hence, this study investigated glucose control and glycaemic variability during free-living conditions in apparently healthy men in relation to cardiorespiratory fitness (CRF) and dietary glycaemic load (GL). Twenty-seven apparently healthy men of varying CRF levels and aged between 30 –47years, were included in the study. The participants underwent at least 7 days of CGM, while logging all food and drink. A modified treadmill Vam-éval ramp test was completed to measure peak aerobic exercise capacity. Each participant had blood samples drawn for the measurement of HbA1c and completed a 2-h 75 g oral glucose tolerance test (OGTT) during which [glucose] and [insulin] was measured every 30 minutes. Inferential statistical analysis was done using Excel, while Cohen’s effect sizes were calculated to describe the magnitude of differences between sub-groups. CFR was best correlated to insulin sensitivity (HOMA-IR: r= -0.74; Matsuda index: r= 0.72), while dietary GL correlated most strongly with MAGE (r= 0.45). A K-means cluster analysis of the dietary macronutrient composition of the participants revealed three groups: high carbohydrate-low fat, low carbohydrate-high fat, and high-carbohydrate-high fat. The high carbohydrate-low fat cluster had the highest glycaemic variability, while the insulin levels were highest in the high carbohydrate-high fat cluster. No differences between clusters were found in traditional glucose control measures. The variation in the OGTT [insulin] was significantly more than the variation in [glucose]. Glycaemic variability indices did not identify more at-risk individuals than were identified with the traditional measures of glucose control. This study could not vouch for early health risk detection among healthy, non-diabetic individuals using CGM. The results, however, showed that dietary macronutrient composition elicited larger differences in glycaemic variability, than in glucose control. Overall, it was evident that increases in insulin secretion occurs before there are any sustained increases in glucose levels.This study provides evidence for the importance of both CRF and diet in the maintenance of metabolic health, as well as the importance of measuring insulin concentrations. Healthy, glucose tolerant individuals are not necessarily protected against hyperinsulinaemia after a high-carbohydrate meal. It is proposed that attention should shift from the measurement of glucose to the measurement of insulin for early risk detection -at least until future longitudinal studies are able to link risk to different glycaemic variability profiles.