**Preface to "The Effect of Diet and Nutrition on Postprandial Metabolism"**

Humans feed themselves by discontinuous inputs that give an essentially dynamic characteristic to all nutritional processes. Metabolism is constructed according to a nutritional system: The individual's endogenous metabolism works on a fasting basis at a steady-state to ensure physiological functions with consistency, but this situation results in molecule/nutrient losses that must be compensated for by food intake. In the postprandial phase, conversely, the nutritional system must ensure the correct use of the influx of nutrients, by regulating flows while maintaining circulating concentrations within acceptable ranges. The postprandial phase is, therefore, the critical nutritional phase during which the body ensures its repletion while putting its homeostasis under pressure, and manages metabolic disturbance according to "hemodynamic" type processes. A decrease in good postprandial management capacity compromises the nutritional status of an individual, on the one hand, and, on the other hand, indicates alterations in metabolic health, i.e., a loss of metabolism flexibility and adaptability. The effectiveness of nutrient use in the postprandial phase appears to be a major determinant of long-term nutritional status for many nutrients. If we consider the resilience of the body to environmental stimuli as a central and modern definition of health, then we can view the smooth course of these postprandial processes as a definition of nutritional health. The efficiency of nutrient use and the time course of the activation of nutrient metabolism is modulated by the characteristics of the diet, patterns of intake, nature of the meals, individual genetics, phenotypes and health status, and all other lifestyle characteristics.

Changes in postprandial metabolism have been considered to be potential early markers in the pathophysiological course, leading to the risk of pathology development. They are sensitive to diets and the complex nature of meals, which can alter the allostatic load, and postprandial deregulations are predictive of the risk of chronic diseases.

With this Special Issue, we aimed to expand and add to the research on the importance of postprandial metabolism in nutrition. The book begins with two long reviews of the literature to understand the appearance of markers of altered cardiometabolic health in the postprandial phase, as well as what is known about its modulation by nutritional intakes, with a detailed review on the importance of modulation of postprandial lipemia. This is complemented by an original research paper on the nature of dietary lipids. Another article focused on the likely important mechanism of postprandial regulation, which is the appearance of low-grade endotoxemia, while another contribution has tended to rule out the possibility that arginine methylation processes, which lead to the appearance of cardiovascular risk factors, may be operating in the postprandial phase. This set provides a rather important overview of the presentation of postprandial processes and their determinants. The global and exploratory understanding of postprandial changes in metabolism is also addressed here, with metabolomics data allowing comparison between "normal" postprandial situations (i.e., after a standard meal) and situations resulting from an acute or prolonged nutritional challenge. Other data help to understand the re-organization of inter-organ flows in response to overnutrition, particularly during the postprandial phase. The last part of the book presents studies that account for the effects of meal composition on postprandial phenomena. It includes several studies that have focused on what has long been the poor relation of the nutritional regulation of postprandial metabolism: proteins. These studies illustrate that proteins themselves, or depending on their relationship with other nutrients (sucrose, lipids), may (1) have different levels of effectiveness in postprandial repletion in subjects with anabolic resistance, (2) modify postprandial metabolic responses in healthy or at-risk subjects, and (3) limit metabolic deregulation leading to ectopic lipid deposition—a highly pathogenic phenomenon. These studies illustrate the current vitality of this topic, which is decidedly modern because it offers a consistent conceptual framework for understanding the relationship between diet and health.

> **Fran¸cois Mariotti , Dominique Dardevet** *Editors*

*Review*
