*Corresponding author e-mail; crmoreno@usp.br Introduction: Studies indicate that night work is associated with metabolic alterations. These include obesity, elevated serum lipids, hypertension among others. In addition, a few laboratory studies have been performed to evaluate the effects of different diets on sleepiness. It has been suggested that there is a decrease of alertness with a high-carbohydrate diet. This study aims to compare the effects of high-protein and high-carbohydrate night meal on sleepiness among night security guards, according to their body mass index. Methods: Twenty-four night security male guards who work from 00:00 to 08:00h (Monday to Friday) volunteered to participate on this study. The guards average age was 30.8 yo (SD= 5.5 yo); body mass index was 28.7 kg/m2 (SD= 4.0 kg/m2) and waist was 106.2 cm (SD= 10.4 cm). They wore an actigraph for three weeks, five days a week (Monday to Friday), to estimate their sleep-wake cycle, which was confirmed by a daily sleep log. Karolinska Sleepiness Scale (KSS) was used to self-record sleepiness every three hours from waking up to going to bed. The first week was considered the baseline and the workers had the night meal they usually ate at work. In the second week, the night meal was exchanged by a high-carbohydrate diet, and in the third week the content of the night meal was high-protein. The workers did not know about the contents of the meals. An ANOVA considering time as repeated measurement (before and after the night meal), and body mass index as a factor (above 30 kg/m2 and below 30 kg/m2) was performed for each condition. Pos-hoc tests were calculated whenever necessary. Results: The analysis found a time borderline effect for the baseline week (p=0.05). It was also found an interaction effect between time and body mass index for the week with high-carbohydrate meal (p<0.05). The workers with body mass index above 30 kg/ m2 were sleepier than the others after eating the high-carbohydrate meal. There were no significant effects observed for the week with high-protein night meal. Conclusion: The results suggest that night meal content does have an effect on night worker sleepiness. However, this effect seems to be modulated by weight. Support: Fapesp 2008/09034-7 Publication History Article published online: 16 June 2026 © 2009. Brazilian Sleep Academy. This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/) Thieme Revinter Publicações Ltda. Rua Rego Freitas, 175, loja 1, República, São Paulo, SP, CEP 01220-010, Brazil
Nehme et al. (Thu,) studied this question.