Temporal Patterns of Eating and Diet Composition of Night Shift Workers Are Influenced More by Shift Type than by Chronotype.

Background/Objectives: Shift work and chronotype influence timing and type of food consumed, yet their combined influence is unclear. This study determined differences between temporal patterns of eating (times of first (FEO), last (LEO), and largest eating occasions (LarEO), duration of eating window (DEW), eating frequency) and nutrient intake of night shift workers on and off shift and the additional influence of chronotype. Methods: Participants (46.6 ± 10.2 years, BMI: 33.9 ± 5.6 kg/m2, male/female: 57/72) completed work/sleep/food diaries, and the Composite Scale of Morningness. Dietary profiles were characterized by day type as follows: morning shift (MS), 1st night shift (1stNS), subsequent night shifts (SNS), 1st day off after night shifts (1stDONS), or other days off (DO). Results: Across day types, there were significant differences in FEO (p < 0.001), LEO (p < 0.001), LarEO (p = 0.025), DEW (p < 0.001), eating frequency (p = 0.003), total energy (p = 0.022), and fibre intake (p < 0.001). Compared to MS, all night shifts had later FEO, LEO, and LarEO; 1stNS had longer DEW and higher fibre but no differences in frequency, energy, and macronutrient intake. Greater morningness was associated with earlier FEO, LEO, LarEO, and lower %energy from fat and saturated fat. Effect of chronotype on temporal eating patterns was not different across day types; there was a significant, positive relationship between morningness and %energy from carbohydrate (%EnergyCHO) on MS (p = 0.004) and 1stDONS (p = 0.040). Conclusions: Dietary habits of night shift workers vary by shift schedule and degree of morningness. Further studies will confirm if shift schedule is more influential than chronotype on shift workers' dietary habits.