Circadian rhythms and appetite

All unapproved Citizendium articles may contain errors of fact, bias, grammar etc. A version of an article is unapproved unless it is marked as citable with a dedicated green template at the top of the page, as in this version of the 'Biology' article. Citable articles are intended to be of reasonably high quality. The participants in the Citizendium project make no representations about the reliability of Citizendium articles or, generally, their suitability for any purpose. This article is currently being developed as part of an Eduzendium student project in the framework of a course entitled Appetite and Obesity at University of Edinburgh. The course homepage can be found at CZ:(U00984) Appetite and Obesity, University of Edinburgh 2010. For the course duration, the article is closed to outside editing. Of course you can always leave comments on the discussion page. The anticipated date of course completion is 01 February 2011. One month after that date at the latest, this notice shall be removed. Besides, many other Citizendium articles welcome your collaboration!

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Sleep deprivation, shift-work and appetite

In modern society, where shopping, eating, working and drinking are widely available 24hours a day, major health implications have been linked as a result. This availability of around the clock activities has defied our bodies internal clock of the vital hours of sleep it requires (Gimble et al., 2009). Over the last few decades where technology and social activities has dramatically advanced, the number of hours of sleep young adults get has decreased within the range of 1-2hours (Spiegel et al., 2004). This is strongly correlated with the prevalence of obesity within the U.K which has shown to have trebled over the last 3 decades (Rennie and Jebb, 2005). Although the rise in this obesity epidemic has been shown to be multi-factorial, sleep deprivation is just another factor to add to the list needing to be addressed in this ever rising health problem .

Figure 1. The relationship between sleep duration and changes in serum leptin and ghrelin levels. (a) Mean leptin levels against average nightly sleep duration. As the number of hours sleep increases the levels of serum leptin also increases. Standard errors for half-hour increments of average nightly sleep. (b) Mean ghrelin levels against total number of hours sleep. As the total number of hours sleep decreases, the mean levels of ghrelin increases. Standard errors for half-hour increments of total sleep time. This figure has been adapted from Taheri et al., (2004).

Several epidemiologic studies have showing sleep deprivation to elevate the levels of the appetite stimulating hormone ghrelin and decrease circulating leptin levels [Fig. 1] (Taheri et al., 2004, Spiegel et al., 2004). These changes in appetite regulatory hormones could be the causes of increased food intake in these sleep deprived adults where a rise in body weight is also observed [Fig. 2] (Taheri et al., 2004).

Figure 2. The relationship between average nightly sleep and changes in body mass index (BMI). As the average nightly hours of sleep decreases below 7 hours, the mean BMI increases. Furthermore, more than an average of 8 hours sleep also causes a rise in mean BMI. Standard errors for 45-min intervals of average nightly sleep. This figure has been adapted from Taheri et al., (2004).

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