The authors examined the associations of shiftwork with overweight and abdominal obesity through a cross-sectional study of 1206 employees 18 to 50 yrs of age who were working on a production line in a poultry processing plant. Night-shift workers (n = 800) were considered exposed, whereas day shiftworkers (n = 406) were considered nonexposed. Overweight was defined as a body mass index ≥25 kg/m² and abdominal obesity as a waist circumference ≥88 cm in women and ≥102 cm in men. The mean age of the workers was 30.5 yrs (standard deviation = 8.7 yrs), and 65.2% were women. Nightshift workers compared to dayshift workers showed higher prevalences of overweight (42.2% vs. 34.3%; p = .020) and abdominal obesity (24.9% vs. 19.5%; p = .037). After adjusting for sociodemographics, parental overweight status, behavioral characteristics, and sleep characteristics, including hours of sleep, the prevalence ratios for overweight and abdominal obesity were 1.27 (95% confidence interval [ CI]: 1.00–1.61) and 1.45 (95% CI: 1.10–1.92), respectively, for the nightshift workers compared to the dayshift workers. A consistent finding in our study was the independent contribution of night shiftwork to overweight and abdominal obesity among Brazilian workers. Further studies are needed to understand the biological mechanisms involved and the complex behavioral and social adaptations experienced by night-shift workers. (Author correspondence: mtolinto@gmail. com )

Objective: The present review aimed to examine the association of eating frequency with body weight or body composition in adults of both sexes.Design: PubMed, EMBASE and Scopus databases were searched. PRISMA and MOOSE protocols were followed. Observational studies published up to August 2016 were included. The methodological quality of the studies was assessed with the Downs and Black checklist.Setting: A systematic review of the literature.Subjects: Adults (n 136 052); the majority of studies were developed in the USA and Europe.Results: Thirty-one articles were included in the review: two prospective and twenty-nine cross-sectional studies. Thirteen per cent of the studies received quality scores above 80 %. The assessment of eating frequency and body composition or body weight varied widely across the studies. Potential confounders were included in 73 % of the studies. Fourteen studies reported an inverse association between eating frequency and body weight or body composition, and seven studies found a positive association. The majority of studies applied multiple analyses adjusted for potential confounders, such as sex, age, education, income, smoking, physical activity and alcohol intake. Six studies took into account under-reporting of eating frequency and/or energy intake in the analysis, and one investigated the mediation effect of energy intake.Conclusions: There is not sufficient evidence confirming the association between eating frequency and body weight or body composition when misreporting bias is taken into account. However, in men, a potential protective effect of high eating frequency was observed on BMI and visceral obesity.

Objective: The objective of our study was to explore the association between sleep deprivation and obesity among shift workers.Design: A cross-sectional study was conducted. Obesity was defined as BMI ≥30 kg/m². Time of sleep was categorized as: >5 h of continuous sleep/d; ≤5 h of continuous sleep/d with some additional rest (sleep deprivation level I); and ≤5 h of continuous sleep/d without any additional rest (sleep deprivation level II). Sociodemographic, parental and behavioural variables were evaluated by means of a standardized pre-tested questionnaire. Potential confounding factors were controlled for in the multivariable model.Setting: A poultry-processing plant in southern Brazil.Subjects: Nine hundred and five shift workers (63 % female).Results: Obesity was more prevalent in the participants who were female, aged 40 years and older, who had less schooling and reported excess weight in both parents. Sleep deprivation levels I and II were associated with increased income, number of meals consumed throughout the day and nightshift work. All of the workers who exhibited a degree of sleep deprivation worked the night shift. After controlling for potential confounding factors, the prevalence ratios of obesity were 1·4 (95 % CI 0·8, 2·2) and 4·4 (95 % CI 2·4, 8·0) in the workers with sleep deprivation levels I and II, respectively, compared with the reference group.Conclusions: These results show a strong association between sleep deprivation and obesity in shift workers and that sleep deprivation may be a direct consequence of working at night.

Objectives: To explore the relationship between work-related stress and obesity among female shift workers. Additionally, we also aimed to test the interaction between shift work and work-related stress in this association.Design: A cross-sectional study was conducted among Brazilian female shift workers. Work-related stress was assessed through a demand–control questionnaire (Job Stress Scale). Work-related stress was defined by the presence of high psychological demands and low control at work. The obesity cases were defined as those with a BMI of 30 kg/m² or more. Multivariate Poisson regression with robust variance was used to obtain the prevalence ratios (PR) and their respective 95 % CI.Setting: A group of industries located in southern Brazil in 2017.Participants: Four hundred and twenty female workers aged 18–59 years.Results: The overall prevalence of obesity was 30 % (95 % CI: 25·6, 34·4), and the presence of work-related stress was identified in 24 % (95 % CI: 19·9, 28·1) of the sample. We found an indication of interaction between work-related stress and night shift work on obesity (P = 0·026). After adjusting for confounding factors, work-related stress was associated with a 71 % greater probability of obesity (PR = 1·71; 95 % CI: 1·02, 2·87; P = 0·042) among female night shift workers.Conclusions: In this study, we revealed that exposure to work-related stress and night shift work were associated with obesity among female shift workers. Furthermore, the prevalence of obesity was high among female shift workers.