CHAPTER 20 Nutrition and the circadian timing system Dirk Jan Stenvers {, *, Cora F. Jonkers { , Eric Fliers { , Peter H. L. T. Bisschop { and Andries Kalsbeek {,} { Department of Endocrinology and Metabolism, Academic Medical Center (AMC), University of Amsterdam, Amsterdam, The Netherlands { Department of Nutrition, Academic Medical Center (AMC), University of Amsterdam, Amsterdam, The Netherlands } Hypothalamic Integration Mechanisms, Netherlands Institute for Neuroscience (NIN), An Institute of the Royal Netherlands Academy of Arts and Sciences (KNAW), Amsterdam, The Netherlands Abstract: Life on earth has evolved under the daily rhythm of light and dark. Consequently, most creatures experience a daily rhythm in food availability. In this review, we first introduce the mammalian circadian timing system, consisting of a central clock in the suprachiasmatic nucleus (SCN) and peripheral clocks in various metabolic tissues including liver, pancreas, and intestine. We describe how peripheral clocks are synchronized by the SCN and metabolic signals. Second, we review the influence of the circadian timing system on food intake behavior, activity of the gastrointestinal system, and several aspects of glucose and lipid metabolism. Third, the circadian control of digestion and metabolism may have important implications for several aspects of food intake in humans. Therefore, we review the human literature on health aspects of meal timing, meal frequency, and breakfast consumption, and we describe the potential implications of the clock system for the timing of enteral tube feeding and parenteral nutrition. Finally, we explore the connection between type 2 diabetes and the circadian timing system. Although the past decade has provided exciting knowledge about the reciprocal relation between biological clocks and feeding/energy metabolism, future research is necessary to further elucidate this fascinating relationship in order to improve human health. Keywords: circadian clocks; circadian rhythm; biological clocks; suprachiasmatic nucleus; glucose; glucose tolerance test; lipids; nutritional sciences; eating; appetite regulation; digestive system; gastrointestinal system; parenteral nutrition; enteral nutrition; diabetes mellitus type 2. Introduction Ever since evolution started, life on earth is sub- ject to the daily rhythm of light and dark. As a consequence, many organisms experience a daily *Corresponding author. Tel.: þ 31 20 5663507; Fax: þ 31 20 6917682 E-mail: d.j.stenvers@amc.uva.nl A. Kalsbeek, M. Merrow, T. Roenneberg and R. G. Foster (Eds.) Progress in Brain Research, Vol. 199 ISSN: 0079-6123 Copyright Ó 2012 Elsevier B.V. All rights reserved. 359 http://dx.doi.org/10.1016/B978-0-444-59427-3.00020-4