Sakurako Oyama

Human reproduction requires females to invest significant energy into pregnancy, lactation, and childcare. Human reproductive ecologists therefore hypothesize that ovarian physiology evolved mechanisms to modulate reproductive effort in response to energy availability. According to the lipostatic model, ovarian function is closely associated with adiposity. In contrast, the metabolic model posits that ovarian function primarily responds to energetic stress. These models remain largely untested among females with high adiposity, which can dysregulate the hypothalamic-pituitary-ovarian axis and disrupt menstrual cyclicity. However, previous studies suggest the reproductive consequences of obesity may be relatively attenuated among Samoan females. This would make possible the characterization of nonpathological variation in ovarian function at the uppermost extreme of human adiposity and broaden our understanding of human reproductive ecology across diverse ecologies. I will first assess the prevalence of menstrual irregularity and anovulation among Samoan females. I will then explore associations between subcutaneous fat mass, energy expenditure on occupational physical activity, and ovarian steroid hormone levels across the menstrual cycle among those with regular, ovulatory cycles. This project will help elucidate how evolutionary and modern ecologies interact to influence female reproductive health in Samoa. It will also shed light on the evolutionary significance of human adiposity.