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Chronobiol Int. 2014 May;31(4):453-60. doi: 10.3109/07420528.2013.821478. Epub 2014 Jan 23.

Effects of a carbohydrate-enriched night meal on sleepiness and sleep duration in night workers: a double-blind intervention.

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Department of Environmental Health, School of Public Health, University of São Paulo , São Paulo , Brazil.


The aim of this study was to investigate the effects of an intervention involving night meal composition on sleepiness and sleep duration in night security guards. A total of 54 male night security guards with a mean age of 30.8 years (SD = 5.5 years) filled out a 24-h dietary recall and were submitted to anthropometric measurement. Twenty-four workers were assigned to the intervention. The intervention was carried out over three consecutive weeks under three conditions. On the first week, no change in workers' food composition was introduced. On the second week, the amount of carbohydrates was increased by 20-30% compared with the first week's intake, whereas during the third week protein intake was increased by 30-40% compared with baseline levels (first week). Throughout the study period, workers wore an actigraph device to estimate sleeping and waking times. A two-factor mixed model analysis with sleep duration as the outcome showed an interaction effect between body mass index (BMI) and condition (F2,56 = 3.9; p = 0.03). Sleep duration was higher in obese workers compared with nonobese workers during the Carbohydrate condition (357 and 267 min, respectively). The analysis of variance (ANOVA) showed an increase in sleepiness under all conditions at 3:00 h (F1,276 = 165.73; p < 0.01) postprandially. A significant difference in sleepiness was also found between the obese and nonobese groups (F1,276 = 14.8; p < 0.01). The effect of the night meal content on sleep duration seems to be mediated by BMI. A carbohydrate-rich meal increased the duration of sleep in obese workers, and may therefore also influence sleepiness.

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