RESUMO
This systematic review aimed to evaluate the association between fixed night work and overweight or weight gain. PubMed and EMBASE were searched until October 2021 for studies evaluating the association between fixed night work patterns and the risk of overweight or obesity (for cross-sectional designs) or weight gain (for longitudinal designs). The outcomes extracted were mean body mass index (BMI), mean BMI difference, overweight %, obesity %, odds ratio, relative risk, and prevalence ratio. The quality of the report was evaluated using the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) checklist. The protocol was registered at PROSPERO (# 42017080515). In total, 25 studies met the inclusion criteria. All studies were observational, 16 were cross-sectional, three were cohorts (two also had baseline cross-sectional data), and the other eight were cross-sectional at baseline and had longitudinal follow-up studies (six prospective cohorts, one retrospective, one interventional). Most had good reporting quality. The fixed night work definition and weight outcomes varied according to the different studies. Most of them found an association between fixed night work and overweight, obesity, or weight gain. This systematic review reinforces the evidence that fixed night work is associated with overweight or obesity, and prolonged night work exposure leads to weight gain. Future research should be conducted with more accurate measures and a prospective design. Fixed night workers should be monitored and advised, especially those with prolonged exposure.