Following the Industrial Revolution, societies structured time around a work-life dichotomy, with conventional working hours dominating until the mid-20th century. However, technological and economic advancements led organizations to extend work schedules to 24/7 operations, resulting in nonstandard work arrangements such as shift work, night work, and weekend work (1). Shift work is generally defined as a work schedule where different teams rotate to cover most or all of the 24-hour day (2). Shift work is performed by around 15% to 20% of employees in Europe, 20% in the US, 6% to 32% in Asia and 8% in Poland (3). One of the sectors in which shift work is comon is the healthcare sector. Paramedics, nurses and doctors represent the medical professions (4).

The work system has an impact on both lifestyle and health. Research highlights shift work and night work as the most detrimental schedules, negatively affecting workers' health, family and social life, and overall organizational dynamics (4, 5). A widely debated issue is the impact on the health of people working different schedules (day, night or rotating) (6). People who work night shifts and rotating shifts often face greater health risks than their daytime counterparts. The health implications for people with different working patterns go beyond metabolic syndrome and risk factors such as obesity (7). Studies suggest that night shift work can elevate the risk of several health problems such as cardiovascular diseases, gastrointestinal disorders, psychological problems and even certain cancers, particularly breast and colorectal cancer (8–11). This increased risk is attributed to circadian disruption. Circadian disruption affects biological functions, alters hormone levels and leads to sleep disturbances (1).

Shift work is a critical factor influencing eating behaviors. Shift work has been found to be associated with higher food insecurity among US workers, indicating a lack of access to adequate nutrition (12). This is particularly relevant for healthcare workers who work non-standardized hours and face difficulties in maintaining a healthy diet due to disrupted dietary patterns. The literature has shown that shift workers, particularly night shift workers, tend to make unhealthy food choices, including greater consumption of sandwiches, cakes, potato chips, and biscuits, fried foods and lower intake of fruit and vegetables, compared to their day shift colleagues (13–15). Moreover, the timing of food intake is crucial. It has often been observed that night eating patterns that deviate from traditional mealtimes can lead to adverse physiological outcomes among night shift workers (16). Inappropriate meal times can affect the body's circadian rhythms. Furthermore, this dietary change can exacerbate health problems, as poor eating habits are associated with an increased risk of cardiometabolic disease among shift workers.

Additionally, the unique working conditions and stress associated with healthcare roles can further complicate nutritional status. A study reported that high stress levels can lead to unhealthy eating behaviors, contributing to deteriorating health markers like obesity (6). Similarly, Gao et al. identified a clear association between shift work and adverse health outcomes, reinforcing the notion that shift work affects nutrition and other health parameters (17).

In this context, hedonic hunger represents a key psychological mechanism through which occupational stress, circadian disruption, and constrained food environments may shape eating behavior among shift-working healthcare professionals. Hedonic hunger refers to a reward-driven tendency to consume palatable foods in the absence of physiological need, reflecting heightened sensitivity to food-related cues. In shift work, it is conceptualized as a context-sensitive disposition that may be amplified under conditions of stress, fatigue, and circadian disruption, rather than as a stable personality trait. These conditions are particularly relevant for healthcare professionals working shifts. There is a consensus that healthcare organizations should establish interventions that promote healthier eating habits among shift workers, but there are no evidence-based nutrition guidelines specifically tailored for shift workers. This is vital not only for individual health but also for the overall effectiveness of healthcare service delivery, as poor nutrition can hinder job performance and quality of patient care (18). Addressing nutritional deficiencies and promoting better health practices among shift-working healthcare workers is essential for improving their well being and working conditions. Therefore, the aim of this study was to evaluate the relationship between ultra-processed food (UPF) consumption, hedonic hunger and mental health among shift-working healthcare professionals.

The internal consistency of the measurement tools used in the study was evaluated using Cronbach's alpha coefficients. The PFS-Tr demonstrated excellent internal consistency (α = 0.946). Similarly, the DASS-21 showed very high reliability (α = 0.943). The FCQ exhibited excellent internal consistency (α = 0.923), while the sQ-HPF demonstrated acceptable internal consistency (α = 0.744).

Table 1 shows the demographic characteristics of the participants. A total of 326 (66.9% female) shift-working healthcare personnel completed the study. Most of the participants (79.8%) worked on night and morning and/or afternoon shifts, 15.6% on night and day shift and/or afternoon and 4.6% on night only.

Table 2 shows the demographic characteristics of continuous variables. The mean age of the participants was 30.00 ± 7.23 years, and the mean BMI was 24.87 ± 3.98 kg/m². The mean shift time of participants was 19.57 ± 7.21 h.

Table 3 presents the distribution of hedonic hunger, food choice, and UPF consumption according to shift duration tertiles. Significant differences were found in sQ-HPF scores (p: 0.029), depression (p < 0.001), stress (p: 0.007), and anxiety (p: 0.002) between shift duration tertiles. Gender comparisons revealed significant differences in PFS-Tr total score (p: 0.003), its subscales, sQ-HPF (p: 0.005), FCQ (p: 0.048), and anxiety scores (p: 0.048). The sQ-HPF, stress and anxiety differences were observed between tertiles 1 and 2, while the depression difference was observed between tertiles 1 and 2 and 3. According to sQ-HPF classification, most of the participants were in the high level UPF consumption group (63.2%), while there was a significant difference between genders (p: 0.010).

Age was weakly and negatively correlated with PFS-Tr total score (r: – 0.143, p < 0.05), food available (r: – 0.140, p < 0.05), sQ-HPF total score (r: – 0.246, p < 0.001) and anxiety score (r: – 0.155, p < 0.05) and weakly and positively correlated with BMI (r: 0.232, p < 0.001). BMI showed a weak positive correlation with food present (r: 0.150, p < 0.05) and sQ-HPF (r: 0.153, p < 0.05). PFS-Tr total score showed weak positive correlations with sQ-HPF total score (r: 0.172, p < 0.05), FCQ total score (r: 0.275, p < 0.001), depression score (r: 0.163, p < 0.05), stress score (r: 0.222, p < 0.001) and anxiety score (r: 0.157, p < 0.05). The sQ-HPF total score was weakly positively correlated with depression (r: 0.174, p < 0.05), stress (r: 0.168, p < 0.05) and anxiety scores (r: 0.179, p < 0.001) (Table 4).

Table 5 shows the stepwise linear regression predicting hedonic hunger. In Model 5, BMI (β: 0.456, p: 0.017), sQ-HPF (β: 0.538, p: 0.048), and stress (β: 0.609, p: 0.018) were significant predictors, accounting for 12.4% of the variance. Gender, and age were consistently significant predictors across all models.

Table 6 presents regression results for sQ-HPF. Model 5 indicates BMI (β: 0.111, p: 0.005) and PFS-Tr (β: 0.030, p: 0.013) as significant predictors. The model explained 16.1% of the variance. Although stress was added in the final model, it did not remain a significant independent predictor.

A series of mediation analyses were conducted to examine whether stress, depression, anxiety, and BMI mediated the relationship between hedonic hunger and UPF consumption. Hedonic hunger significantly predicted all three psychological variables—stress (B: 0.077, p < 0.001), depression (B: 0.075, p: 0.002), and anxiety (B: 0.066, p: 0.004)—each of which in turn significantly predicted UPF consumption: stress (B: 0.098, p: 0.004), depression (B: 0.091, p: 0.006), and anxiety (B: 0.086, p: 0.010). In all three models, hedonic hunger remained a significant predictor of UPF consumption when the mediator was included (B values ranged from 0.026 to 0.028), indicating partial mediation. In contrast, although BMI was a significant predictor of UPF (B: 0.099, p: 0.010), it was not significantly predicted by hedonic hunger (B: 0.028, p: 0.089); therefore, BMI did not meet the criteria for mediation. Furthermore, the total FCQ score was examined as a mediator. Hedonic hunger significantly predicted the FCQ total score (B: 0.405, p < 0.001), which in turn negatively predicted UPF consumption (B: −0.021, p: 0.034). When both variables were included, hedonic hunger remained a significant predictor (B: 0.034, p: 0.003), indicating a partial mediation with an inverse relationship. The total effect value remained constant across all models, as it was derived from the same base regression model without mediators, confirming the consistency and validity of the analysis (Figure 1). These findings reflect statistical indirect associations observed within the sample and do not establish causal directionality between hedonic hunger, psychological variables, BMI, and UPF consumption.

To the best of our knowledge, this is the first study to comprehensively evaluate the relationship between hedonic hunger, level of UPF consumption, and mental health parameters among shift-working healthcare professionals. Rather than novelty by population alone, the present study contributes by empirically demonstrating how hedonic hunger was statistically linked via psychological stress to influence UPF consumption within a circadian-disrupted occupational context. Although the study does not include a non–shift-working comparison group, its primary objective was not to contrast occupational groups, but to examine the internal psychological pathways linking hedonic hunger to UPF consumption within a population already known to be metabolically and psychologically vulnerable. Shift work constitutes a high-risk context characterized by circadian misalignment, elevated stress, and constrained food environments; therefore, identifying mechanisms within this group has direct clinical and occupational relevance. The findings revealed that 63.2% of participants were classified as high level UPF consumption, with hedonic hunger emerging as a significant predictor of UPF intake through both direct and indirect pathways—particularly via stress and FCQ. Furthermore, participants working longer shifts reported significantly higher levels of UPF consumption, depression, anxiety, and stress. These results underscore the multifactorial nature of dietary behaviors in shift workers, shaped not only by occupational demands but also by underlying psychological mechanisms, highlighting an urgent need for integrated nutritional and mental health strategies in healthcare settings.

Psychological distress is notably prevalent among healthcare shift workers, especially those on night shifts. Studies have shown that this group is more vulnerable to irritability, stress, depression, and anxiety, largely due to factors such as job insecurity, sleep disruption, and sustained exposure to infectious environments (28–30). Consistent with this evidence, our study found that participants working longer shifts (>24 h) reported significantly higher depression, anxiety, and stress scores compared to those with shorter shift durations. Moreover, gender-based comparisons revealed that female shift workers experienced significantly higher anxiety levels, reinforcing the notion of a gendered vulnerability in mental health outcomes, which is in line with previous findings identifying younger female non-physician staff as a particularly at-risk group (29). Beyond descriptive trends, our regression and mediation analyses demonstrated that stress significantly mediated the relationship between hedonic hunger and UPF consumption, underlining the indirect impact of psychological burden on dietary behavior. Although depression and anxiety were also tested as potential mediators, their effects were less pronounced, suggesting that stress may serve as the primary psychological conduit through which emotional drivers translate into unhealthy food choices. These findings further support the view that mental health is not only a personal well being concern but also a determinant of health behavior, particularly in demanding shift-based healthcare roles. Furthermore, the mediation findings should be interpreted with caution. Although the analytical models were specified with hedonic hunger as the independent variable, this does not imply that hedonic hunger causally precedes psychological distress or BMI. Dominant models of eating behavior emphasize that psychological distress and environmental stressors often shape eating patterns rather than emerge from them. In line with this literature, the present findings are best viewed as exploratory and hypothesis-generating, highlighting potential psychological pathways that warrant further examination in longitudinal or experimental designs. It should also be acknowledged that the observed effect sizes were small and the explained variance was modest. This is consistent with the multifactorial nature of eating behavior, suggesting that hedonic hunger and psychological variables represent partial contributors rather than dominant determinants of UPF consumption. Accordingly, the findings should be interpreted as indicating meaningful but limited associations within a complex behavioral system.

Shift workers, particularly nurses and emergency medical personnel, frequently experience circadian rhythm disruptions due to irregular work schedules, which in turn contribute to erratic eating patterns and a heightened susceptibility to hedonic hunger, a form of appetite driven by the rewarding aspects of food rather than physiological necessity. Previous research has linked elevated stress, anxiety, and depression levels in female shift workers to maladaptive eating behaviors, such as emotional and external eating, as well as restrained eating related to BMI increases (31). Supporting these findings, our study revealed that hedonic hunger was significantly associated with UPF consumption, and that stress partially mediated this relationship. Furthermore, female participants had significantly higher levels of hedonic hunger, anxiety, and UPF consumption, suggesting a gendered vulnerability consistent with earlier literature.

In our sample, 63.2% of participants were classified as high-level of UPF consumers, and those working longer shifts (>24 h) exhibited significantly higher UPF intake as well as elevated depression, anxiety, and stress scores. These patterns align with previous evidence indicating that shift workers often compensate for fatigue and psychological strain by skipping meals, snacking more frequently, and opting for energy-dense, nutritionally poor foods (15, 32, 33). These behaviors are further reinforced by environmental factors—such as limited access to healthy food options during night shifts—which increase reliance on hedonic, convenience-based eating (16). Additionally, our findings showed that FCQ was negatively associated with UPF intake, suggesting that individuals who place greater emphasis on deliberate food choice considerations may be less likely to translate hedonic hunger into higher ultra-processed food consumption.

Circadian misalignment may be associated with hormonal fluctuations, particularly in cortisol and ghrelin levels, which disrupt normal hunger cues and amplify hedonic drives toward UPF consumption (34). This misalignment has also been implicated in the development of metabolic syndrome and obesity among shift workers (35, 36). Within this context, our study provides novel evidence that hedonic hunger functions not only as a direct predictor of UPF consumption but also as a psychological mechanism operating through stress, mood disturbances, and motivational drivers, highlighting the multifaceted vulnerability of healthcare shift workers to unhealthy dietary behaviors.

This study highlights the significant interplay between hedonic hunger, UPF consumption, and psychological distress among shift-working healthcare personnel. The findings indicate that hedonic hunger is a key factor influencing dietary behaviors in this population, both directly and indirectly through elevated stress levels and food choices. A substantial proportion of participants exhibited high levels of UPF intake, particularly those working extended shifts and female staff members, who also reported higher anxiety and hedonic hunger scores. These results highlighted the urgent need for integrated interventions addressing both nutritional and mental health challenges in shift-working healthcare personnel. Tailored workplace policies, improved food environments, and psychological support services may offer effective strategies for mitigating the negative health impacts associated with shift work.

This study has certain limitations, including its cross-sectional design, reliance on self-reported measures, and the restriction of the sample to healthcare shift workers from a single institution, which may limit causal inference and generalizability. Future studies using longitudinal designs, objective dietary assessments, and intervention-based approaches are warranted to further elucidate the mechanisms linking hedonic hunger, psychological distress, and ultra-processed food consumption.