Fat oxidation at rest and during exercise in postmenopausal middle eastern and white women
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Background: The declining levels of estrogen and progesterone during the menopausal transition predispose women to an increase in overall body mass and altered adiposity distribution that may place them at risk for developing cardiometabolic disease. Estrogen, progesterone and testosterone levels have been linked to changes in lipid metabolism and since these hormone levels change during the menopausal transition they may contribute to the unfavorable alteration in body composition. Differences in fat oxidation rates (FOR) have been observed between ethnic groups and the hormonal modifications that occur after menopause have been speculated to influence these differences. Only select ethnic groups have been studied, and exploring additional groups will allow further understanding of the menopausal transition and FOR. Purpose: The purpose of this study was to compare resting FOR, FOR during incremental exercise and FORmax, hormone levels, anthropometric characteristics, physical activity (PA) levels and cardiometabolic risk factors between Middle Eastern (ME) and W postmenopausal women. Results: Significant differences between groups were observed are as follows; the ME women were younger (p= 0.004), observed their first period at an earlier age (p= 0.023) and had their last menstrual cycle early in life (p= 0.031). Time since first and last cycle was shorter in the ME group (p= 0.007). ME had a higher body mass (p= 0.027), a higher body mass index (p= 0.32) and a larger waist circumference (p= 0.005). W women had a higher peak aerobic capacity (p=0.003) and higher self-reported levels of PA (p=0.017). Discussion: The ME women did not exhibit lower FOR at rest, during incremental exercise or at maximum exercise and ME women did not have a lower level of estrogen or have more cardiometabolic risk factors than the W women. This study sheds light on FOR within a new ethnic group of postmenopausal women not yet investigated. As well, data on FOR, FORmax and the exercise intensity expressed as a percentage ofV02 peak, at which maximal fat oxidation occurs using a treadmill protocol and hormonal measurements for ME and W postmenopausal women. A treadmill protocol was created and used which provided whole-body FOR at multiple sub-maximal PA intensities. PA levels and anthropometrics were also obtained in this study providing detailed data on the health and fitness characteristics of the study populations.