How Timing of Eating May Affect Shift Workers' Health: A Review and Future Ideas

Shift workers work outside the conventional hours of 08:00 h and 18:00 h [1], which may include permanent shifts or combinations of rotating evening, night, split, on‐call or 24‐h shifts [2]. In 2023, 14.5% of employees in Australia usually performed shift work [3], with the main industries including mining, healthcare and accommodation and food services [4]. Compared with day‐working counterparts, shift workers have a greater risk of diabetes (14% higher risk) [5], cardiovascular diseases (17% higher risk) and coronary heart disease morbidity (26% higher risk) [6], with night shift work being classified as ‘probably carcinogenic to humans’ by a working group at the International Agency for Research on Cancer [7]. Although the health risks for shift workers may be attributed to lifestyle factors such as smoking or social and domestic stress [8], there are pathways to disease development that stem solely from being awake at night, a time typically associated with rest and recovery.

This is problematic because for shift workers, work hours occur when the body should be at rest, as dictated by our internal circadian rhythm, which is regulated by a central clock in our suprachiasmatic nucleus. This clock oscillates in approximate 24‐h cycles, kept in synchrony with the outside world through the light/dark information transmitted to the clock through our eyes [9]. The central clock coordinates with peripheral clocks located in organs throughout the body through hormonal and neuronal signals to determine our sleep/wake cycle, feed/fast cycle and regulation of physiological processes [9]. For example, metabolic processes (such as insulin secretion, glucose metabolism, diet‐induced thermogenesis and lipid metabolism) peak in the day and decline at night, with late night food consumption resulting in perturbations to metabolic profiles [10, 11, 12, 13, 14, 15, 16]. Additionally, night shifts cause the sleep/wake cycle and feed/fast cycle (internal biological clock) to desynchronise with the 24‐h light/dark cycle, resulting in circadian misalignment [17, 18]. Circadian misalignment leads to impaired glucose tolerance and raised levels of inflammatory markers and blood pressure in both healthy adults [19, 20, 21] and long‐term shift workers (who performed ≥ 12 months of shift work) [22, 23]; with chronic circadian misalignment linked with an increased risk of diabetes, overweight and obesity and metabolic syndrome [24, 25, 26, 27].

There is a growing interest in the cardiometabolic health effects of the temporal pattern of food intake over the 24‐h day/night cycle, known as chrononutrition [28], which holds relevance for night shift workers [28]. Temporal aspects of food intake that impact cardiometabolic health outcomes include duration of eating window (DEW), timing, frequency and regularity of food intake (Figure 1) [28; 29]. Previous reviews before 2020 of shift workers have described their eating patterns and associated health risks [30, 31, 32], reasons behind their dietary choices [32, 33] and dietary interventions [34]. However, the reviews do not consider advantages from, or barriers to, changing food timing, nor include performance outcomes, which may be affected by changing food intake across a shift. This information is critical, not only for shift workers, but also for organisations and healthcare professionals to optimise workplace health promotion and medical chrononutrition therapy and to highlight research gaps to advance the field of chrononutrition.

This narrative review aims to provide an update of recent evidence since 2020 and (i) characterise the temporal eating patterns of shift workers across different shift types to highlight their eating patterns; (ii) discuss and evaluate relationships between timing of food intake, and the health and performance outcomes in observational and intervention studies on shift workers or in simulated shift work; and (iii) summarise translational potential for clinical practice and future directions in the chrononutrition management of shift worker health.

A search was conducted on MEDLINE, Embase and APA PsycInfo using keywords related to “shift work”, “shift schedule”, “chrononutrition”, “temporal patterns of food intake” (such as timing, frequency and regularity). The search was limited to articles published from 2020 to 2025, written in English, including adult human participants (aged 18 years and older) and excluded animal studies.

A series of chrononutrition terms were identified in a previous Delphi study as important concepts for examination among shift workers, including DEW, distribution of food intake across different shift types and days off and frequency of food intake [29].

Higher risks of poorer metabolic health, including higher cardiovascular disease risk, are observed in night shift working populations who eat later at night [46, 47] or have a longer DEW [47] compared with individuals who did not, after adjusting for confounders. The mechanisms that contribute to these associations include disturbances in lipid, insulin and glucose profiles, resulting from a combination of circadian misalignment from shift work and mistimed food intake.

A controlled laboratory study demonstrated the nadir in the circadian rhythm of triglyceride metabolism occurred at night and the resultant elevation in triglyceride levels from night‐time food consumption [48]. Similarly, glucose tolerance was poorer when young healthy participants consumed food at night in a simulated shift work study [49] and among permanent night/rotating shift workers in a randomised controlled crossover study comparing high sugar meals consumed at night during a night shift to in the day during a day shift or day off [50]. In contrast, limiting food intake to the daytime during simulated shift work allowed endogenous circadian glucose rhythms to remain unchanged from baseline and synchronised to the central clock rhythm, avoiding glucose intolerance [49]. Additionally, significantly higher overall mean 24‐h insulin levels have been observed for night shift workers than for day shift workers in an observational study, with eating at night associated with more than two times greater insulin levels [51]. No differences in insulin levels between day and night shift workers were observed when eating was primarily in the daytime [51]. This highlights the benefits of eating in the day, in synchrony with the circadian rhythm despite performing shift work.

To minimise the metabolic consequences of night‐time eating, studies have investigated the potential benefits of avoiding (fasting) or minimising food intake at night on metabolic health outcomes.

The impact of fasting from 22:00 h until 06:30 h during two night shifts, compared with two nights of consuming a meal at 02:00 h, was compared in male police officers. Fasting on night shifts resulted in significantly lower morning insulin levels and insulin resistance, than in the individuals who did not fast [52]. However, the overnight fast resulted in a higher consumption of calories during the subsequent day compared with the individuals who did not fast [52]. Although fasting prevented unwanted increases in glycaemic responses at night, the higher subsequent energy intake could have implications for weight gain if sustained.

Time‐restricted eating (TRE) has become a popular practice for the management of weight and several metabolic conditions [53]. In a 12‐week study (n = 137), firefighters who worked 24‐h shifts were randomised to receive either standard of care (SOC; nutritional counselling for the Mediterranean diet) or SOC and 10‐h of TRE (self‐selected eating window) during the day. Although there were no between‐group differences in energy intake or body mass index (BMI), both groups reduced energy intake, and the TRE group had a significant decrease in body weight and BMI. Additionally, post hoc analyses revealed that individuals with higher glycated haemoglobin levels or blood pressure at baseline experienced improvements to those parameters with SOC plus TRE but not SOC alone. The metabolic benefits found in this study were likely due to the rearrangement of energy intake towards daytime hours, and demonstrated that implementing a self‐selected TRE window plus SOC was as effective as using SOC alone and a suitable alternative among shift workers, with suggested benefits accrued by individuals with increased cardiometabolic disease risk [54].

Metabolically, shift workers may benefit from fasting at night, but a qualitative study found that consumption of food during night shifts also serves the purpose of social bonding, improving team moral and maintaining alertness [55]. In a simulated shift work study in Japan, 15 healthy adults were provided a snack at 03:30 h during the night shift and exhibited better cognitive performance than without a snack [56]. Additionally, in shift‐working nurses in the Netherlands, a greater eating frequency was associated with greater alertness, measured by a faster reaction time and a lower number of lapses, although the type or size of meals consumed is not clear [57]. These studies recognise the importance of food intake at night for maintaining work performance, but cardiometabolic health outcomes were not investigated. Maintaining performance is an important factor to consider for shift workers with high workload or where mental acuity is crucial for safety. Hence, some studies have investigated shortening the duration of fasting [58] or introducing the concept of intermittent fasting [59]; while others manipulated the caloric load [60] or frequency of food provided while adjusting its content [61].

Two randomised controlled trials restricted food intake on night shifts to address the challenges of entirely omitting food consumption during night shifts [58, 59]. In a randomised crossover feasibility study in Australia, permanent or rotating night shift workers with abdominal obesity who usually ate between 01:00 h and 06:00 h on night shifts were asked to avoid food consumption during that window for 4 weeks [58]. This resulted in a significant reduction in body weight and BMI, while maintaining similar energy intake between intervention and control periods (habitual food intake) [58].

Although the weight change observed in the previous study was not clinically relevant, it informed the development of a weight loss trial (Shifting Weight using Intermittent Fasting in night shift workers (SWIFt) study) among 250 night shift workers in Australia [59]. The trial examined the effectiveness of modified intermittent fasting (IF) by limiting energy intake to 500 kcal on either day shifts/days off (IF: 2D) or night shifts (IF: 2N) with no restriction on other days, compared with control (continuous energy restriction [CER] of 20% of estimated energy requirements [EER]) [59]. After 24 weeks, weight loss and decreased insulin resistance were observed in all groups, with no significant differences between either IF or CER groups [59]. All groups also experienced significant improvements from baseline in fasting insulin levels, blood pressure, waist circumference, BMI and fat/fat free mass [59]. This study demonstrated three potential strategies for night shift workers to successfully lose weight, with the IF: 2N group providing a mechanism to minimise overnight eating [59]. A qualitative study of a subset of study participants reported that fasting on only 2 days a week was straightforward to follow and easy to integrate into work schedules [62]. Participants did not find fasting at night to be disruptive as it did not interfere with day‐time social activities; however, those whose work schedule required fasting on back‐to‐back days (common for rotating shift workers), reported side effects including headaches, hunger and nausea, that improved with strategies provided by study dietitians [62].

The impact of snacks compared with meals during simulated or actual night shifts has also been tested to determine if caloric load of each instance of food intake at night matters. In a simulated shift work study in Australia, 55 healthy, non‐obese adults were randomised to either fast at night, snack at night (10% of EER), or have a meal (30% of EER) at night (00: 30 h) [60]. Although impairment in glucose tolerance was less after a snack compared with a meal, glucose tolerance was impaired compared with no energy intake at all, highlighting the significance of a fast for glucose homeostasis [60]. The authors noted that altering the macronutrient content of study food to be higher in protein and lower in carbohydrates may lead to different results, requiring further investigation [60]. Another study in the Netherlands also manipulated the frequency (1 meal vs. 3 meals) and content (high glycaemic index (GI) vs. low GI) of food consumed at night [61]. In comparison with not having meals during night shifts, consuming low GI meals led to less hunger and did not worsen glucose homeostasis, regardless of meal frequency [61, 63]. Congruently, consuming high GI meals, regardless of frequency, led to worse glucose variability metrics. Low GI meals also reduced the number of lapses in a psychomotor vigilance test compared with high GI meals [63]. Incorporating low GI food options is a simple approach that could limit glycaemic impairment while supporting alertness associated with shift work [63].

Data in this review support found that consumption of small amounts of food at night maintained work performance. Previous studies (published before the timeframe of this review) found less sleepiness and improved cognitive performance (reaction time, psychomotor vigilance and running memory) with either consumption of a snack or meal compared with food avoidance [64, 65]. What is less clear is when and what to eat, to minimise the impact on metabolic health without compromising work productivity and safety. Future studies need to fill knowledge gaps by examining the concomitant effects of small amounts of food at night on cardiometabolic health outcomes, cognitive performance measures and physiological comfort. Additionally, organisational support is necessary for timely breaks and the provision of healthy food, which is often cited as a barrier [33, 66]. Altogether, these steps are necessary to ensure dietary recommendations to shift workers are not just effective, but also practical and sustainable in the long term.

Studies from different industries and countries demonstrate consistently that shift workers' food intake is characterised by irregular timing, including food intake throughout the night while working night shifts and prolonged eating windows on first night shifts. Late night food intake impairs glucose and lipid profiles, with long‐term implications of heightened risks of cardiometabolic diseases. These impacts of shift work are different for each shift worker. The short‐term exposure to shift work by rotating medical interns is likely very different to those exposed to chronic shift work. From a chrononutrition perspective, minimising energy intake at night is beneficial in the limited number of studies available, but its long‐term sustainability and outcomes in shift workers with pre‐existing cardiometabolic diseases has yet to be determined (Figure 2). If food is to be consumed for performance and safety, identifying exactly when and what to eat during the night shift with minimal metabolic consequences needs to be further investigated.

Moving forward, improving shift worker health by optimising their diet should be approached from three angles (Table 1). At the individual level, shift workers should be conscious of meal timing and ensure that meal composition is aligned with the Australian Guide to Healthy Eating [67]. Additionally, approaching dietary adjustments collectively with colleagues may make change easier. At the organisational level, employers should support shift workers by removing barriers to healthy eating, consistently highlighted as poor availability of healthy food at night and the lack of time to consume meals or prepare healthy food during shifts [55, 68]. Enablers to eating earlier on night shift have been reported to include scheduled meal breaks and workplace nutritional education programs [66]. A recently developed chrononutrition questionnaire, which captures temporal patterns of eating across different shift types in 10–15 min [29, 69], may be used by organisations in collaboration with Accredited Practising Dietitians familiar with the principles of chrononutrition to design workplace health promotion programs to improve the temporal eating patterns of their unique employee populations. As healthcare professionals, dietitians may additionally provide tailored nutrition education to at‐risk individuals, with referrals to medical professionals or holistic care and follow‐up as necessary [70]. The healthcare system, with the second highest proportion of shift workers of any industry in Australia (32%) and as major providers and advocates of optimal health, should lead shift work industries in supporting its shift‐working employees in consuming timely, healthy food to optimise their health [4].

Conceptualisation: Yan Yin Phoi, Alison M. Coates; Methodology, Writing – review and editing: Yan Yin Phoi, Maxine P. Bonham, Michelle Rogers, Jillian Dorrian, Alison M. Coates; Data curation: Jillian Dorrian, Yan Yin Phoi; Formal analysis, Investigation, Project administration and Writing – original draft: Yan Yin Phoi; Supervision and Validation: Maxine P. Bonham, Michelle Rogers, Jillian Dorrian, Alison M. Coates; Resources: Alison M. Coates.

The authors declare no funding sources.

Commissioned; externally peer reviewed.

The authors declare no conflicts of interest.

Open access publishing facilitated by Adelaide University, as part of the Wiley ‐ Adelaide University agreement via the Council of Australasian University Librarians.

There are no data in this manuscript.