Meal Patterns, Physical Activity, Sleep and Circadian Rhythm

Assessment of food and energy intake takes place in the context of research on metabolic health and energy balance. However, as the metabolic processes of the ingested food depend on the time of ingestion on a day, timing of meals, and the relation to circadian rhythms should be taken into account. According to Froy (2007), Wolk and Somers (2007), Kohsaka et al. (2007), Mendoza (2007), Mendoza et al. (2008), Adamantidis and de Lecea (2008), Bechtold (2008), Laposky et al. (2008), Esquirol et al. (2009), Scheer et al. (2009), Arble et al. (2009), Garaulet et al. (2010), Cagampang and Bruce (2012), coordination of daily patterns of activity, feeding, energy utilization, and energy storage is supported by a synchronized pattern of release of the relevant endocrine components across the 24-hour cycle (see Figure 6.1). The master circadian clock, namely the suprachiasmatic nucleus (SCN) of the hypothalamus provides circadian alignment, and connected peripheral tissues of the body containing the molecular clock machinery and subsequently addresses the local circadian oscillation and rhythmic gene expression. However, metabolic processes are decoupled from the primarily light-driven SCN when food intake is desynchronized from normal diurnal patterns of activity resulting in changes in energy availability, substrate oxidation, storage, and metabolic status. If feeding becomes the dominant entraining stimulus, adaptation to the changed food intake patterns occurs, facilitated by an autonomous food entrainable oscillator (FEO) that governs behavioral rhythms. Consequently, energy metabolism can influence the clock mechanism of the SCN. This close interaction is critical for normal circadian regulation of metabolism, and desynchronization may underlie the disruption of proper metabolic rhythms observed in metabolic disorders, 114 such as obesity and type 2 diabetes (T2D) (Bechtold 2008; Esquirol et al. 2009; Arble et al. 2009; Hoogerwerf 2009; Schibler et al. 2003; Knutsson and Boggild 2010; Szosland 2010).