Doctoral Dissertation Improvement: Impacts of Food Processing on Diet-Induced Thermogenesis

所有的人类社会都经常通过加热和非加热的方式来加工食物。这一特征将人类与其他物种区分开来，从能量的角度来看，这甚至可能是强制性的，因为我们拥有相对较小的臼齿和胃肠道，这使我们不得不接受易于消化的饮食。然而，食品加工的能量意义及其进化意义几乎没有被考虑过。这项研究测试了这样一种假设，即加热和非加热处理降低了食物消化的代谢成本，即饮食诱导产热(DIT)。将评估块茎和肉类的影响，这些食物被人类广泛开发，被认为是祖先原始人的关键资源。从理论上讲，加工这些食物应该会导致结构完整性的丧失，这是因为减少了咀嚼和胃的努力，以及增加了消化酸和酶的进入，从而降低了DIT。由于高温会使淀粉和胶原蛋白糊化，从而在更大程度上削弱食品结构的完整性，因此进一步预测，热加工的效果将超过非热加工的效果。为了评估这些预测，根据平衡的受试者内设计，通过呼吸测量从受试者那里收集了标准化膳食前后的能量消耗数据，这些食物包括生的和整的，生的和捣碎的，烤的和整的，或者烤的和捣碎的。为了低成本和高控制性，大鼠将被用作模型生物，但将使用人类受试者来重复试验的子集，以验证动物模型。这项研究将量化热处理和非热处理对DIT的影响，DIT是能量平衡的重要因素。结果将提高我们对食品加工的能量回报的理解，并为人类向更高饮食质量过渡的模型提供信息。低密度被认为是导致肥胖的一个因素。通过确定食品加工对DIT的影响，这项研究提供了基本数据，可以帮助消费者影响膳食能量对新陈代谢和身体储存的分配。因此，结果将在人类学和营养学方面的同行评议期刊和会议以及公共论坛上广泛传播。这项博士论文研究项目也将有助于一名女性研究生的专业发展。

All human societies regularly process their foods by thermal and non-thermal means. This feature distinguishes humans from other species, and may even be compulsory from an energetic perspective, given that we possess relatively small molars and gastrointestinal tracts that commit us to an easily digestible diet. Yet the energetic significance of food processing and its evolutionary implications have barely been considered. This study tests the hypothesis that thermal and non-thermal processing lower the metabolic cost of food digestion, known as diet-induced thermogenesis (DIT). Effects will be evaluated for tubers and meat, foods widely exploited by humans and believed to have been critical resources for ancestral hominins. In theory, processing of these foods should result in a loss of structural integrity that lowers DIT due to reduced chewing and gastric effort, as well as increased access by digestive acids and enzymes. Since heat should weaken food structural integrity to a greater extent by gelatinizing starch and collagen, it is further predicted that the effects of thermal processing will exceed those of non-thermal processing. To evaluate these predictions, energy expenditure data are collected via respirometry from subjects before and after standardized meals served raw and whole, raw and pounded, roasted and whole, or roasted and pounded, based on a counterbalanced within-subjects design. Rats will be used as model organisms in the interests of low cost and high control, but a subset of trials will be replicated using human subjects to validate the animal model. This study will quantify the impacts of thermal and non-thermal processing on DIT, an important factor in energy balance. Results will improve our understanding of the energetic returns of food processing and inform models of hominin transitions toward higher dietary quality. Low DIT has been implicated as a factor in the development of obesity. By determining the effects of food processing on DIT, this research contributes basic data that could help consumers influence the partitioning of meal energy to metabolism versus body stores. Results will thus be communicated broadly to peer-reviewed journals and conferences in anthropology and nutrition, as well as public forums. This doctoral dissertation research project will also contribute to the professional development of a female graduate student.