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

人类生殖生态学的研究为进化如何塑造生殖机制（例如，排卵、妊娠和哺乳）以适当地响应环境环境提供了关键见解。例如，生理机制会降低已经处于哺乳期或能量储存较低的妇女的排卵功能。然而，哺乳在很大程度上不受低能量储存的影响，因为当母亲的能量被分配时，这一过程被赋予了代谢优先权。虽然大多数这类研究都集中在营养紧张的人群上，但最近的研究表明，超重的女性患哺乳期功能障碍的几率更高。与正常体重的女性相比，超重的女性产后开始哺乳的时间较晚，如果已经开始，停止母乳喂养的时间也会更早。从生殖生态学的角度来看，这一结果令人惊讶，因为超重的女性有充足的哺乳所需的能量储存，而且新陈代谢通常优先于哺乳。尽管研究一致报告了产妇肥胖与哺乳期开始晚和持续时间短之间的联系，但这种关系的原因尚不清楚。这个项目将关注的核心问题是：为什么超重的女性有泌乳功能障碍的风险？由于建立和维持牛奶产量的过程取决于生理、行为和社会条件的精细调节，因此本研究将利用生物文化方法。来自明尼阿波利斯的孕妇。保罗将被招募参加配对病例对照研究。数据将通过三种方法收集：首先，产前调查将调查社会心理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他们决定断奶的因素，以测试行为模式与母亲肥胖的关联。最后，将抽取血清样本来测试肥胖和非肥胖女性之间的激素差异。统计分析将确定产妇肥胖、激素浓度、行为模式和社会心理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。随着全球肥胖率的持续上升，揭示这群女性面临泌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可以利用的知识奠定基础，以传播关于超重妇女在尝试母乳喂养时面临的特殊问题的信息。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，并将使预测导致泌乳性能差的近似机制更容易。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相关的权衡的知识。它将解决（储存的）代谢能量过剩如何干扰对生殖至关重要的能量要求任务的执行这一难题。在这样做的过程中，它将有助于理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.