Night-eating syndrome is associated with food consumption frequency among Chinese college students

In 1955, Stunkard first reported that patients with night-eating syndrome (NES) exhibited circadian rhythm dysfunction¹, suggesting an imbalance between eating and sleep patterns². The syndrome is defined as a daily intake of > 25% of the recommended calorie intake after dinner, accompanied by nocturnal eating at least twice a week for a minimum of 3 months³. It is characterized by morning anorexia and hyperphagia in the evening (awakening to eat during the night), along with difficulties in both falling asleep and maintaining sleep¹. NES is associated not only with physical conditions such as obesity and diabetes^4,5, but also with a range of other health issues, including insomnia, depression, and anxiety⁶. These comorbidities can significantly affect overall well-being and quality of life. Thus, examining the association between NES and lifestyle, particularly dietary habits, is crucial for understanding its potential risks and consequences.

Individuals with NES often display irregular nighttime eating habits, which may influence daytime eating behaviors and contribute to an overall imbalanced diet.Previous studies in patient populations and healthy adults have demonstrated significant correlations between NES and specific dietary preferences. For example, a study of obese individuals in Pakistan revealed a positive correlation between NES and frequency of daily snacking⁷. Another study in adults revealed that NES was positively associated with unhealthy dietary habits, such as the consumption of sugary beverages and fast food, and negatively associated with healthy eating habits, such as the consumption of fruits and vegetables⁸. Furthermore, the association between NES and breakfast frequency has been explored in studies involving Bangladeshi university students, Turkish pregnant women, and patients with type 2 diabetes in the United States. These studies reported a statistically significant inverse association between NES and breakfast intake^5,9,10, while no significant associations were observed for lunch or dinner consumption in patients with type 2 diabetes⁵.

A significant proportion of university students engage in unhealthy eating patterns at night. Previous research indicates that 57.10% of university students regularly consume late-night snacks, with 6.79% eating late-night snacks every night, 23.15% eating late-night snacks frequently, and 27.16% eating late-night snacks occasionally¹¹. The university years represent a critical period in the transition from adolescence to adulthood¹² and for the development of long-term eating habits, which can influence both short-term and chronic health outcomes. Despite several studies investigating the association between NES and dietary behaviors, there remains a lack of research examining associations between NES, food consumption frequency, and meal regularity among Chinese populations, particularly among college students. Accordingly, this study used a cross-sectional design to examine the association between NES and both single and multiple dietary consumption frequencies. Moreover, this study aims to provide data that may inform strategies for promoting healthier dietary habits and identifying target populations for potential interventions among Chinese college students.

Table 2 presents the sociodemographic characteristics of the participants. A total of 11,856 college students participated, of whom 33.3% were male, with a mean age of 18.8 years. Among participants, 34.6% had an annual household income of > 35,000 yuan, and 58.9% resided in rural areas. Approximately one-third had parents with a bachelor’s degree or higher.

After adjusting for potential confounders, this study found statistically significant associations between NES levels and several dietary and meal frequency outcomes. Specifically, higher frequency of fruit consumption classified as unhealthy according to the scoring criteria.was associated with NES (mild group: OR = 3.796, 95% CI: 3.264–4.414; severe group: OR = 2.674, 95% CI: 1.899–3.763;P for trend < 0.001). The same was observed for vegetable consumption frequency (mild group: OR = 2.773, 95% CI: 2.386–3.222; severe group: OR = 1.865, 95% CI: 1.345–2.586༛P for trend < 0.001), snack consumption frequency (mild group: OR = 0.593, 95% CI: 0.499–0.705; severe group: OR = 1.240, 95% CI: 0.889–1.729༛P for trend = 0.001), soft drink consumption frequency (mild group: OR = 0.633, 95% CI: 0.542–0.740; severe group: OR = 1.195, 95% CI: 0.867–1.648; P for trend = 0.001), irregular breakfast consumption (mild group: OR = 1.347, 95% CI: 1.155–1.572; severe group: OR = 1.196, 95% CI: 0.852–1.677; P for trend = 0.001), and irregular lunch consumption (mild group: OR = 1.292, 95% CI: 1.090–1.531; severe group: OR = 1.671, 95% CI: 1.166–2.394; P for trend < 0.001) compared with the normal group. However, no significant associations were observed between NES levels and the consumption frequency of other food items or dinner frequency (Figs. 1 and 2).

To date, studies on the effect of NES on food consumption frequency have primarily focused on the association between NES and a single food consumption frequency^7,8 or the frequency of three meals per day^5,9,10. To our knowledge, this is the first study to examine the associations between NES and food consumption frequency as well as meal frequency in college students. Our findings indicate that individuals with NES tended to report a higher consumption frequency for high-calorie foods, such as sugary beverages and snacks, and lower consumption frequencies for vegetables and fruits compared with those without NES. Conversely, students without NES were more likely to maintain regular breakfast and lunch patterns than those with NES. These findings are consistent with those from previous investigations. However, in contrast to previous studies, we used a representative sample of Chinese university students to comprehensively examine the association between NES and a range of food consumption frequencies and meal frequencypatterns.

Regarding potential mechanisms underlying the association between NES and food consumption frequency, it is plausible that endogenous circadian rhythms mediate this effect. Hunger exhibits a circadian rhythm, peaking in the evening (around 8 p.m.) and reaching its lowest point in the morning (around 8 a.m). The influence of circadian rhythms on the appetite for specific food groups was is more pronounced in the evening, which is associated with an increased desire for high-energy foods such as sweets, salty snacks, carbohydrates, meat, poultry, and fruits. In contrast, there is less evidence of a circadian influence on the appetite for low-energy foods such as vegetables¹⁷. Thus, individuals with NES, characterized by nocturnal eating, may experience a heightened evening appetite driven by circadian rhythm, contributing to increased intake of high-energy foods¹⁸ and reduced appetite during the day, leading to irregular meal patterns¹⁹.

Changes in appetite-related hormones, such as leptin, may also play a role. Sleep suppresses appetite by prompting the release of leptin, which is produced by adipocytes^20,21. This suppression persists during the morning wake state. In contrast, NES is characterized by nighttime and nocturnal hyperphagia, morning purging, and insomnia, accompanied by a reduction in leptin levels during nocturnal sleep periods. This may result in increased hunger and subsequent food intake²², as supported by a cross-sectional study showing a significant positive association between NES and leptin levels²³.

Beyond the biological mechanisms, behavioral and lifestyle factors specific to university students may further amplify the association between NES and food consumption frequency. For instance, academic pressure can cause worry, which may lead to overthinking or engaging in entertainment activities, such as using phones or tablets, that can delay bedtime^24,25 and mealtimes^26,27, increase cognitive load²⁸, raise energy expenditure²⁹, and ultimately stimulate appetite for high-energy foods³⁰.

Notably, this study identified a significant association between severe NES and reduced frequency of breakfast and lunch consumption. The schedules of Chinese university students may be a contributing factor to the difficulties experienced by nocturnal eaters in consuming breakfast and lunch. Breakfast is typically served between 7 a.m. and 9 a.m. The schedules of the first and second classes (at 8 a.m. and 10 a.m., respectively) influence students’ eating habits, particularly for nocturnal eaters, who may have no choice but to eat between classes. Furthermore, the proximity of breakfast to lunchtime makes it challenging for nocturnal eaters to reach sufficient hunger to eat lunch. In a study of Chinese university students (both male and female), approximately 40% consumed breakfast at least 30 min after awakening, whereas approximately 20% did not consume breakfast at the optimal time^31,32.

This study has some limitations that should be considered when interpreting the findings. First, the cross-sectional design precludes the determination of causal relationships between NES, food consumption frequency, and meal frequency. Second, the self-reported nature of meal frequency data, collected based on participants’ recall of generic meal categories (breakfast, lunch, and dinner) without reference to specific timeframes, may introduce recall bias and lead to misclassification of meal patterns. Future research should employ more precise dietary assessment tools, such as 24-h dietary recalls, food frequency questionnaires, or food diaries, to evaluate the quantity and quality of food consumption more accurately. Third, although the depression scale used in this study includes items that conceptually overlap with stress and anxiety symptoms, these individual questions cannot fully assess a person’s stress or anxiety levels. Therefore, future studies should incorporate validated questionnaires assessing anxiety and stress to clarify whether these factors, as potential confounders, affect the association between NES and eating behaviors.

In conclusion, the results suggest a strong association between NES and food consumption frequency and meal regularity. Individuals with severe NES may exhibit irregular meal patterns and increased consumption of high-energy foods. These findings emphasize the importance of interventions targeting NES, which may help students modify their food choices and establish consistent habits of consuming three balanced meals daily. Future research should employ longitudinal, prospective, or randomized controlled designs to validate and extend these findings.

We thank all of the college students who agreed to participate and provided informed consent. We also acknowledge our staff for their dedicated work.

ZH: Conceptualization, Software, Writing – original draft, Data curation, Writing – review & editing. XG: Conceptualization, Methodology, Software, Writing – review & editing. QJ: Software, Formal analysis, Data curation, Writing – original draft, Writing – review & editing. BZ: Conceptualization, Methodology, Writing – original draft, Writing – review & editing. MH: Conceptualization, Methodology, Formal analysis. ZR: Conceptualization, Methodology, Formal analysis, Investigation, Resources, Writing – original draft, Writing – review & editing, Supervision, Funding acquisition.

This study was supported by the Chongqing Municipal Social Science Planning Project - Youth Project (Grant No. 2021NDQN66), and the Ministry of Education of Humanities and Social Science project - Youth Project, China (Grant No. 21YJCZH125), and the Science and Technology Research Program of Chongqing Municipal Education Commission (Grant No. KJQN202300230).

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.