Eating and Working in the Night: Desinchrony and Disease

*Corresponding author e-mail: escocarolina@gmail.com Shiftand night — work lead to internal desynchronization characterized by loss of phase relation between behavioral, hormonal, and metabolic rhythms. In the long-term night and shift work lead to cardiovascular and gastric disorders, propensity to obesity, metabolic syndrome and cancer. In order to better understand the mechanisms underlying the internal desinchrony in the night worker, we have developed an experimental model of night-work in rats based on daily schedules of forced activity during the resting phase. From Monday to Friday rats are placed for 8 hours in slow rotating wheels during the light phase (from 9 AM to 5 PM). During the remaining hours of the day and during weekends rats are returned to their individual home cages in a monitoring system in order to register their spontaneous activity. After 4 weeks under this “working” schedule the amplitude of daily activity rhythms is significantly diminished and rats voluntarily shift their food ingestion towards “working” hours. Consequently metabolic rhythms are dampened and uncoupled from the SCN, exhibiting peak values during the light phase, when rats are “working”, while the activity in the SCN measured with c-Fos and Perl immunohistochemistry, remains coupled to the LD cycle. Follow up of Fos and Perl daily cycles in hypothalamic structures indicate that their daily activity shifts to the “working” schedule and thus also is uncoupled from the SCN. Since feeding schedules are strong entraining signals for peripheral oscillators, metabolism and behavior, we explored whether the modified feeding patterns developed by working rats could have promoted the internal desinchrony. By restricting feeding schedules for working rats towards the night, and preventing rats to eat during their “working schedules” the disturbance in metabolic rhythms was prevented and working rats limited to eat during the night showed similar diurnal patterns as ad libitum controls. However working and control rats scheduled to eat only during the light phase developed disturbed metabolic rhythms and significantly increased body weight. Our study evidences the deleterious effects of shifted feeding schedules towards the resting phase and points out the relevance of feeding schedules to prevent internal desinchrony in the night worker. Support: This study was supported by CONACyT 43950-M; CONACyT 82462 and PAPIIT- UNAM IN-203907. 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