Background

The prevalence of bariatric surgery has seen a steady increase impacting the lives of over 14.6 million individuals [1]. For patients with class II and III obesity, bariatric surgery represents a transformative journey, leading to significant weight loss and substantial improvements in physical health [2]. Notable one-year post-surgery outcomes include reduced waist circumference, lower glucose and insulin levels, decreased free fatty acids and triglycerides, and a modest increase in high-density lipoprotein levels [3]. However, this path to weight reduction often intersects with the challenges posed by eating disorders.

A formal diagnosis of eating disorders has been linked to post-bariatric surgery patients, some resorting to spontaneous or forced vomiting as a means of weight control [4]. Cravings, more prevalent in this group than in healthy-weight controls, add another layer of complexity [5]. Furthermore, night-eating disorders have surfaced as a noteworthy concern post-surgery, with patients describing symptoms persisting for up to eight years following the procedure [6]. The foundational work of Stunkard et al. [7] introduced the concept of Night-Eating Syndrome (NES), characterized by minimal breakfast intake, consumption of over 25% of daily calories after dinner, and disrupted sleep patterns. Mood disorders, poor sleep quality, metabolic syndromes, obesity, and eating disorders are among the factors associated with NES [8]. To diagnose NES, specific criteria must be met, including the consumption of at least 25% of daily intake after dinner and nighttime awakenings occurring at least twice a week for a minimum of three months [9]. NES has been found to affect 1.5% of the general population in the United States and 1.5% of adult Omani residents [10, 11].

Recent studies highlight the challenge of NES in post-bariatric patients, with an observed increase in NES behaviors two to three years post-surgery [12,13,14,15]. A retrospective analysis in Bahrain linked eating disorder behaviors with diminished postoperative weight outcomes, emphasizing the importance of addressing these behaviors [16]. Variability in NES prevalence has been documented, ranging from 1.9 to 8.9% depending on the diagnostic criteria, which underscores the complexity of diagnosing and managing NES [17]. While these studies underscore the importance of understanding nighttime eating habits and their impact on the outcomes of weight-loss therapy, only a limited number of investigations have been conducted in Saudi Arabia, examining the relationship between NES and postoperative prognosis.

The present study aims to bridge this knowledge gap by investigating the prevalence and risk factors associated with NES in patients who underwent bariatric surgery at King Abdulaziz University Hospital in Saudi Arabia.

Methods

Study design

This cross-sectional study employed a self-administered, web-based survey through Google Forms. The study was conducted in collaboration with the Family Medicine Department and the Obesity Clinic at the Medical Nutrition Unit of King Abdulaziz University Hospital in Jeddah, Saudi Arabia, from June to November 2022.

Study participants

The study included adult men and women who had undergone bariatric surgery, were 18 years of age or older, and had a postoperative follow-up period of 1 year. Pregnant women in the postoperative phase were excluded from the study.

Study instrument

The survey encompassed thorough inquiries into the following areas:

  1. 1.

    Demographics and clinical history: Participants were requested to provide details regarding their age, gender, and nationality. Furthermore, they were asked about any chronic medical conditions, including hypertension, dyslipidemia, and diabetes mellitus type 2.

  2. 2.

    Anthropometric measurements: Respondents were required to report their height in centimeters (cm) and their weight in kilograms (kg), both before the bariatric procedure and one-year post-procedure.

  3. 3.

    Type of bariatric procedure: Information was collected on the specific bariatric surgery procedure undergone by the participants.

  4. 4.

    Night Eating Questionnaire (NEQ): The NEQ was employed as a primary diagnostic tool to identify the presence and severity of Night Eating Syndrome (NES) among participants. This questionnaire is a validated self-report instrument designed to capture the distinctive behaviors and patterns associated with NES. It comprises multiple items that ask respondents about their eating habits, specifically focusing on the timing and quantity of food consumption. Key aspects evaluated by the NEQ include the proportion of daily caloric intake consumed after the evening meal, incidents of nocturnal eating (defined as waking during the night to eat), mood fluctuations related to eating times, and sleep disturbances influenced by eating patterns. A critical threshold, a global NEQ score of 25 or higher, was adopted based on established diagnostic criteria to identify individuals likely to have NES.

Statistical analyses

Data analysis was performed using SPSS software, version 20 (IBM, Armonk, New York, USA). Descriptive statistics were applied to summarize mean, standard deviation, and to provide frequency counts and percentages for categorical variables. The chi-squared test was utilized for examining associations among categorical variables, and the Mann–Whitney U test for analyzing continuous data. Spearman’s test was used for correlation analysis. Multivariate logistic regression analysis was carried out to identify factors independently associated with NES among participants. This analysis incorporated variables selected for their potential relevance to NES, with odds ratios calculated at a 95% confidence interval. A P value of less than 0.05 was considered statistically significant for all tests.

Ethical considerations

This study received approval from the Research Ethics Committee of the Unit of Biomedical Ethics at the Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia (Approval Number: 322 − 22). Prior to participation, all individuals gave their written informed consent, adhering to the ethical guidelines and ensuring the confidentiality and anonymity of their responses.

Results

Participant characteristics

In our assessment of 371 individuals, 154 patients were identified as meeting the study’s inclusion criteria. The demographic breakdown revealed 83 patients (53.9%) were female, and 130 patients (84.4%) were of Saudi nationality. The mean age of participants was 38.8 ± 11.4 years. Prior to undergoing bariatric procedures, the average weight of these individuals was 125.1 ± 29.0 kg, which significantly decreased to 80.5 ± 18.1 kg following the procedures. Correspondingly, the mean Body Mass Index (BMI) was reduced from 44.8 ± 8.2 kg/m² to 28.9 ± 5.8 kg/m². Sleeve gastrectomy was the predominant bariatric procedure, conducted on 131 patients (85.1%). Chronic diseases were reported by 109 patients (70.8%), with hypertension being the most commonly reported condition by 44 patients (28.8%). Furthermore, 41 patients (26.6%) reported adherence to a post-procedure diet (Table 1).

Table 1 Demographic and clinical characteristics of post-bariatric surgery patients evaluated for Night-Eating Syndrome (N = 154)
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Factors associated with night-eating syndrome

Of the participants, 52 (33.8%) scored 25 or higher on the NEQ, indicating the presence of NES. Analysis showed non-significant negative correlations between NEQ scores and age, sex, as well as pre- and post-procedure weights and BMIs (Table 2). Notably, the prevalence of NES was significantly higher among female patients, with 35 females (42.2%) affected, compared to males, where 41 (57.8%) were found to have NES (P = 0.017). Among chronic conditions, diabetes was significantly associated with NES (P = 0.025), unlike other conditions examined in this study (Table 3).

Table 2 Correlation between physical characteristics and Night Eating Questionnaire scores in post-bariatric surgery patients
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Table 3 Characteristics of patients with and without Night-Eating Syndrome in post-bariatric procedure patients
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Multivariable regression analysis model

The logistic regression analysis identified significant determinants of NES (Table 4). Being female was associated with an elevated risk of NES (OR: 2.33; 95% CI: 1.05–5.19; P = 0.030), and the presence of chronic diseases significantly increased the risk of NES (OR: 32.95; 95% CI: 2.33–464.44; P = 0.010). Specifically, diabetes mellitus was associated with a higher prevalence of NES (OR: 2.63; 95% CI: 1.23–5.88; P = 0.013).

Table 4 Determinants of Night Eating Syndrome in post-bariatric procedure patients: a logistic regression analysis
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Discussion

This study aimed to evaluate the prevalence of NES in patients who had undergone bariatric surgery at King Abdulaziz University Hospital. Our findings shed light on the prevalence rates and associated factors of NES in this specific patient population and contribute to the growing body of knowledge on eating disorders post-bariatric surgery.

According to the NEQ, our study identified that 33.8% of patients in our sample met the criteria for NES. This prevalence rate aligns with previous research findings in the field. For instance, a study conducted in the United States found that 25% of overweight and obese patients exhibited NES symptoms after bariatric surgery [15]. However, variations in NES prevalence across studies may be attributed to differences in sample sizes and diagnostic criteria used for NES assessment.

Our study further delved into the demographic characteristics of patients with NES. The mean age of patients with NES in our study was 38.8 years, which is in line with similar studies that have reported relatively young ages among NES-affected individuals [18, 19]. This finding aligns with epidemiologic data indicating that NES tends to be less frequent among individuals over 65 years of age [11].

An intriguing finding in our study was the significantly higher prevalence of NES among female patients compared to male patients. This observation echoes the outcomes of previous investigations [15, 20] and reflects the well-established fact that women are more prone to developing eating disorders [21].

A notable finding in our study was the association between NES and chronic illnesses, particularly diabetes. A previous study conducted in the United States on patients with obesity and type 2 diabetes also identified NES as the most prevalent eating disorder in this population [22]. This reinforces the relationship between NES and metabolic conditions, as well as the impact of NES on dietary adherence and mood [23]. Furthermore, our study revealed that the majority of patients with NES underwent sleeve gastrectomy (90.3%). However, we found no significant relationship between NES prevalence and the type of bariatric procedure.

While our study explored various factors, including age, nationality, diet adherence, BMI, and type of bariatric procedure, we did not find any significant associations between these factors and the presence of NES. These results corroborate the findings of previous studies [24, 25]. Our study suggests that NES prevalence among post-bariatric surgery patients may not be strongly influenced by these demographic or clinical factors.

While our study offers valuable insights, it is essential to acknowledge its limitations. As a cross-sectional study, it is susceptible to recall bias. Moreover, the reliance on self-reported data through a questionnaire may introduce inaccuracies. To address these limitations, future research in this area should consider longitudinal designs and incorporate clinical assessments to provide a more comprehensive understanding of NES in post-bariatric surgery patients.

Conclusion

In conclusion, our study contributes to the understanding of NES prevalence and risk factors among patients who have undergone bariatric surgery. The complex relationship between NES, demographic factors, and clinical variables necessitates further research to elucidate its underlying mechanisms and develop targeted interventions. Recognizing NES as part of postoperative care is essential for optimizing long-term outcomes and quality of life for this patient population. Moreover, our findings underscore the importance of continued research in the evolving field of bariatric surgery outcomes and eating disorders.