Application of the physical laws of energy and mass conservation at the whole-body level is not necessarily informative about causal mechanisms of weight gain and the development of obesity. The energy balance model (EBM) and the carbohydrate–insulin model (CIM) are two plausible theories, among several others, attempting to explain why obesity develops within an overall common physiological framework of regulation of human energy metabolism. These models have been used to explain the pathogenesis of obesity in individuals as well as the dramatic increases in the prevalence of obesity worldwide over the past half century. Here, we summarize outcomes of a recent workshop in Copenhagen that brought together obesity experts from around the world to discuss causal models of obesity pathogenesis. These discussions helped to operationally define commonly used terms; delineate the structure of each model, particularly focussing on areas of overlap and divergence; challenge ideas about the importance of purported causal factors for weight gain; and brainstorm on the key scientific questions that need to be answered. We hope that more experimental research in nutrition and other related fields, and more testing of the models and their predictions will pave the way and provide more answers about the pathogenesis of obesity than those currently available.

在全身水平上应用能量和质量守恒定律并不一定能提供关于体重增加和肥胖发展的因果机制的信息。能量平衡模型 （EBM） 和碳水化合物-胰岛素模型 （CIM） 是两个看似合理的理论，以及其他几个理论，试图解释为什么肥胖会在人类能量代谢调节的整体共同生理框架内发展。这些模型已被用于解释个体肥胖的发病机制以及过去半个世纪全球肥胖患病率的急剧增加。在这里，我们总结了最近在哥本哈根举行的研讨会的成果，该研讨会汇集了来自世界各地的肥胖专家，讨论肥胖发病机制的因果模型。这些讨论有助于在操作上定义常用术语;描绘每个模型的结构，特别关注重叠和发散的区域;挑战关于所谓的因果因素对体重增加的重要性的想法;并就需要回答的关键科学问题集思广益。我们希望在营养学和其他相关领域进行更多的实验研究，以及对模型及其预测的更多测试，这将为肥胖的发病机制铺平道路，并提供比目前可用的更多答案。