Doctoral Dissertation Improvement : Biological and Cultural Factors Associated with Lactational Dysfunction in Overweight Women

对人类生殖生态学的研究为进化如何塑造生殖机制提供了关键见解（例如，排卵、妊娠和哺乳）对环境条件作出适当反应。例如，生理机制降低了已经哺乳或能量储存低的女性的排卵功能。然而，哺乳在很大程度上不受低能量储存的影响，因为当母体能量被分配时，该过程被给予代谢优先权。虽然大多数此类研究都集中在营养紧张的人群中，但最近的研究表明，超重女性面临更高的哺乳功能障碍率。与正常体重的妇女相比，超重妇女产后哺乳期较晚，如果建立，停止母乳喂养更快。从生殖生态学的角度来看，这一结果是令人惊讶的，因为超重的妇女有足够的能量储存所需的哺乳期，因为代谢的优先权一般给予哺乳期。虽然研究一致报道了母亲肥胖与晚发和哺乳期短之间的关联，但这种关系的原因仍然未知。这个项目将集中在中心问题：为什么超重的妇女有哺乳功能障碍的风险？由于建立和维持牛奶生产的过程取决于一套精心调整的生理，行为和社会条件，这项研究将利用生物文化的方法。将招募明尼阿波利斯-圣保罗的孕妇参加配对病例对照研究。数据收集将采用三种方法：首先，产前调查将调查心理社会和人口因素如何影响母乳喂养，以测试母亲肥胖与这些因素之间的关系。其次，将观察哺乳事件，参与者将记录母乳喂养的尝试以及影响其断奶决定的因素，以测试行为模式与孕产妇肥胖的关联。最后，将抽取血清样本以测试肥胖和非肥胖女性之间的激素差异。统计分析将确定母亲肥胖、激素浓度、行为模式和心理社会因素对母乳喂养结果的影响的相对贡献。母乳喂养为婴儿及其母亲提供了许多好处。随着肥胖率在全球范围内持续上升，揭示这群女性患哺乳功能障碍风险的原因变得越来越重要。该项目将为公共卫生机构传播关于超重妇女在试图母乳喂养时面临的特殊问题的信息奠定知识基础。阐明这一人群中泌乳功能障碍的原因将有助于解释其他环境和文化背景下的泌乳功能障碍，并更容易预测导致泌乳表现不佳的近似机制。最后，该项目将推进有关现代人类女性如何管理与生殖策略有关的权衡的知识。它将解决一个难题，即过剩的（储存的）代谢能如何干扰繁殖所必需的能量要求高的任务的执行。在这样做的过程中，它将有助于了解支持牛奶生产的生理途径如何与脂肪储存和代谢途径相关。

Studies of human reproductive ecology have provided key insights into how evolution has shaped reproductive mechanisms (e.g., ovulation, gestation and lactation) to respond appropriately to environmental circumstances. For example, physiological mechanisms reduce ovulatory function in women already nursing or with low energy stores. Lactation, however, is largely unaffected by low energy stores as this process is given metabolic priority when maternal energy is partitioned. Though most such studies have focused on nutritionally stressed populations, recent research has demonstrated that overweight women face a higher rate of lactational dysfunction. Compared to normal weight women, overweight women establish lactation later postpartum and if established, stop breastfeeding sooner. This result is surprising from a reproductive ecology perspective because overweight women have ample energy stores needed for lactation and because of the metabolic priority generally afforded to lactation. Although studies consistently report an association between maternal obesity and late onset to and short duration of lactation, the causes of this relationship remain unknown. This project will focus on the central question: Why are overweight women at risk for lactational dysfunction? Because the process of establishing and maintaining milk production depends upon a finely tuned set of physiological, behavioral and social conditions, this research will utilize a bio-cultural approach. Pregnant women from Minneapolis-St. Paul will be recruited to participate in a matched-pair case-control study. Data will be collected using three methods: First, a prenatal survey will investigate how psychosocial and demographic factors influence breastfeeding to test the relationship between maternal obesity and these factors. Second, nursing episodes will be observed and participants will record attempts to breastfeed as well as factors influencing their decision to wean, in order to test the association of behavioral patterns and maternal obesity. Finally, serum samples will be drawn to test hormonal differences between obese and non-obese women. Statistical analyses will identify the relative contribution of the effects of maternal obesity, hormone concentrations, behavioral patterns and psychosocial factors on breastfeeding outcomes.Breastfeeding provides numerous benefits for infants and their mothers. As obesity rates continue to rise globally, it becomes increasingly important to uncover the reasons why this cohort of women is at risk for lactational dysfunction. This project will lay the groundwork for knowledge that can be used by public health institutions to disseminate information on the special problems overweight women face when attempting to breastfeed. Elucidating the causes of lactational dysfunction in this population will help to explain lactational dysfunction in other environmental and cultural contexts and will make it easier to predict the proximate mechanisms leading to poor lactation performance. Finally, this project will advance knowledge regarding how modern human females manage trade-offs relating to reproductive strategies. It will address the puzzle of how a surplus of (stored) metabolic energy can interfere with the performance of an energetically demanding task essential for reproduction. In doing so, it will contribute to the understanding of how physiological pathways supporting milk production relate to pathways of fat storage and metabolism.