UBC Theses and Dissertations
Can eating and body attitudes affect physiological health outcomes in premenopausal women? Prospective 2-year changes in bone, and relationships with ovulation, cortisol and blood pressure. Bedford, Jennifer Lynn
Cognitive dietary restraint (CDR) is the perception that one is limiting food intake in an effort to achieve/maintain a perceived ideal body weight. Cross-sectional studies suggest CDR is associated with an increased frequency of subclinical ovulatory disturbances (%SOD; anovulation and luteal phase <10 days long) and lower bone mass, possibly mediated by cortisol, a stress hormone. This research was conducted to prospectively examine relationships among CDR, %SOD, 24-hour urinary free cortisol (UFC) and 2-year areal bone mineral density change (ΔaBMD) in non-obese, regularly-menstruating women, aged 19-35. To monitor %SOD, least-squares quantitative basal temperature (LS-QBT) analysis was used. LS-QBT was first further validated against urinary pregnanediol glucuronide (PdG), an indirect indicator of ovulation (n=40, Chapter 2). Relative to PdG, LS-QBT showed excellent detection of ovulatory cycles (97%) but poor detection of anovulatory cycles (25%). Estimated day of luteal onset was correlated between methods (r=0.8, P<0.001). Chapter 3 presents prospective findings (n=123). Women with higher CDR had higher %SOD (56% versus 34%, P<0.001) and higher UFC (28.0 µg/day versus 24.0 µg/day, P=0.021). ΔaBMD did not differ by CDR level. Women with higher %SOD had less positive lumbar spine (L1-4; 0.7% versus 1.9%, P=0.034) and hip (-0.6% versus 0.9%, P=0.001) ΔaBMD, and higher CDR scores (8.7 versus 7.1, P=0.04). UFC was not associated with %SOD or ΔaBMD. Whether eating/body attitudes (EBA) were associated with 12-hour daytime ambulatory blood pressure (ABP) was explored as a secondary objective (n=120, Chapter 4). Women with negative EBA had higher diastolic ABP and mean arterial pressure, independently of weight loss effort. Finally, at baseline (n=137, Chapter 5), UFC was inversely associated with total body bone mineral content (BMC; r= -0.30, P<0.001) and aBMD (r= -0.27, P=0.003); L1-4 aBMD (r= -0.19, P=0.035) and BMC (r= -0.18, P=0.049); and hip BMC (r= -0.23, P=0.011), after adjustment for potential confounders. In summary, findings suggest CDR and other negative EBA may be associated with adverse health outcomes including higher ABP and %SOD. Furthermore, more frequent SOD, which are not apparent to women, were associated with less positive ΔaBMD. However, cortisol may not be the only or most important mediator of these relationships.
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