1. Introduction
Irritable bowel syndrome (IBS) is a disorder of gut brain interaction (DGBI), characterized by chronic abdominal pain and altered bowel habits, in the absence of any other disease [
1]. As a common gastrointestinal disease, about 10% to 15% of the world’s population suffers from IBS, and the prevalence in Asia ranges from 6.8% to 33.3% [
2,
3]. Leading to uncontrollable intestinal symptoms, such as constipation and diarrhea, IBS has a marked adverse impact on patients’ quality of life, causing appetite decrease, psychomotor retardation, dysphoria, depression, and other serious issues [
4,
5,
6,
7]. Meanwhile, health care and medication costs remain higher and keep increasing during IBS remission than in other DGBI, which places a heavy burden on the healthcare system [
8,
9]. Moreover, IBS increases patient absence from work, which places stress on a patient’s personal financial life [
9,
10]. Therefore, it is essential to study the risk factors associated with IBS to develop prevention and control strategies. Early life stressors (abuse and psychosocial stressors), antibiotics, enteric infection, and dietary factors have been considered environmental contributors to IBS symptoms worldwide [
11]. Thorough identification of modifiable risk factors is significant in alleviating IBS symptoms.
Eating style is a psychology-related concept known as ‘one’s cues to eat’, including emotional eating, restraint eating, and external eating, which could determine the functioning of both adults and children [
12]. In simple terms, emotional eating is associated with the tendency to eat due to negative emotions; similarly, external eating implies eating stimulated by environmental factors, such as the aroma and appearance of delicious food; restraint eating represents the act of reducing caloric intake for weight control [
13,
14,
15]. According to reports, these eating styles could negatively affect human health, connecting with depression, overeating, and obesity [
16,
17,
18]. Many researchers have proved the association between diet-related risk factors and IBS, such as binge eating, high-calorie food intake, and irregular eating rhythms [
19,
20,
21]. However, few studies have investigated the association between eating styles and IBS. Recently, the prevalence of abnormal eating styles and IBS among Chinese college students remains high [
22,
23]. Thus, evaluating the relationship between them can control IBS symptoms at both the psychological and behavioral levels and provide further insights into the harm of the three eating styles.
Accordingly, we investigated eating styles and IBS prevalence in a representative sample of Chinese medical students and examined the role of the three different eating styles in IBS symptoms. We hypothesize a positive relationship between abnormal eating styles and the odds of having IBS.
4. Discussion
This cross-sectional study showed that, among 2739 Chinese medical students, the total eating styles score and the three eating styles were associated with the odds of having IBS. According to the study results, the risk of IBS of the students with the total scores in tertile 3 was 3.75 times that in tertile 1. Furthermore, the risk of IBS in the tertile 3 of external eating, emotional eating, and restraint eating trends was 3.87 times, 2.71 times, and 3.82 times higher than that of tertile 1, respectively.
In previous studies on IBS and diet-related factors, most explored the impact of dietary content and quantity on IBS. For example, in the Swedish Twin Study of Adults, there was a significant positive association between binge eating and IBS symptoms among 23,821 adults [
32]. An observational study that explored the relationship between IBS and alcohol consumption found a stronger association between binge drinking and the next day’s gastrointestinal symptoms than drinking [
33]. A low-FODMAP diet is characterized by a limited intake of foods containing highly fermentable oligosaccharides, disaccharides, and monosaccharides and polyols (FODMAPs), such as fruits, vegetables, legumes and cereals, honey, milk, and dairy products, which have been shown to have a beneficial effect on IBS-related symptoms repeatedly [
34,
35]. In addition, the connection between unhealthy foods and IBS was also testified. A prospective dietary intervention study for 105 adult IBS patients in Sweden found that IBS patients who ate too much fast and processed food, cereals, and sweets/soft drinks were more likely to suffer from aggravated gastrointestinal symptoms [
36]. In addition, many IBS-related dietary guidelines showed that reducing the intake of caffeine, alcohol, spicy foods, fat, and milk, and increasing the intake of fiber-rich foods should be the first line of treatment for IBS [
19].
Our study compared to the above studies testified to the relationship between eating styles and IBS. Eating styles are related to patients’ eating behaviors and the psychological factors that drive those eating behaviors. Firstly, many researchers have suggested that patients with emotional eating cannot distinguish between hunger and other negative emotions [
37] or choose an inappropriate method to deal with their negative emotions [
38]. Thus, they eat large amounts of food, including highly unhealthy food, to regulate distress, anxiety, stress, and other psychological problems [
39]. Secondly, patients with external eating may be more responsive to external food cues and less sensitive to internal hunger and satiety signals, leading to binge drinking and binge eating when exposed to food-filled environments [
40]. Thirdly, patients with restraint eating often set strict rules to reduce food intake at first. As time passes, the body may not be able to distinguish food shortage from self-imposed food restriction and acts as if in starvation mode, resulting in more hunger and greater appetite than before [
15]. On the other hand, such strict rules will become increasingly difficult to maintain, and the inevitable breaking may induce overeating [
41]. Many researchers have proposed that negative emotions can further weaken the control of diet in patients with external eating and restraint eating, increasing their need for overeating [
37,
40,
42]. In addition, numerous studies have proven that those three eating styles can lead to binge eating [
13,
43,
44,
45,
46], which is associated with IBS. To sum up, by comparing articles that only investigated the relationship between dietary content and IBS, we may have uncovered the possible psychological problems behind the eating behaviors of IBS patients and established a path from psychological factors to eating behaviors to IBS. However, since many studies recommend that IBS patients should choose low-stimulating foods and avoid overeating [
19,
20,
21], most IBS patients also believe that their symptoms are closely related to food [
47], not to mention that IBS symptoms can have a serious negative impact on quality of life [
48]; thus, IBS patients will spare no effort to control their diet. As a result, people with IBS may cause restraint eating because of the restricted diet. Similarly, IBS patients may not overeat when faced with negative emotions and external food stimulation, so it is less likely to lead to emotional eating and external eating. Therefore, we will build cohort studies in the future to find evidence for the relationship between IBS and diet.
We conjecture that there may be two mechanisms for this association. First, eating styles and IBS are related to psychological factors. It is well known that psychological factors are significant contributors to IBS. Stress or negative emotions may cause gastrointestinal symptoms in patients under the effect of the brain–gut axis [
49,
50]. On the other hand, eating style describes eating behaviors as psychological drivers. For example, emotional eating represents eating behaviors that deal with negative emotions through eating [
18,
39,
51]. Likewise, restraint and external eating have also been highly connected with anxiety and depressive symptoms [
52,
53,
54,
55]. Above all, negative emotions are likely to be a key variable affecting emotional eating and IBS, which needs to be further verified in future studies. The second potential mechanism is that abnormal dietary patterns can lead to a high intake of unhealthy foods. The resulting gastrointestinal intolerance and sensitivities to unhealthy foods contribute to developing IBS symptoms [
20].
The limitations of this study are as follows. First, this study was conducted on Chinese medical students, so the results may be neither generalizable to other countries nor necessarily applicable to different age groups. Second, this study is cross-sectional, which means it cannot establish a causal link between IBS and eating style. Third, we only used DEBQ to assess eating styles in this study. The Three-Factor Eating Questionnaire (TFEQ-R21) can also estimate emotional eating. The different assessment instruments may lead to a different association between IBS and eating styles. Forth, there was a selection bias in our study. Due to the higher prevalence of males in the students who agreed to participate in the study, only one-third of the three-hundred and thirty-five students diagnosed with IBS were female, in contrast to the epidemic expectations. Thus, we performed a stratified analysis (
Table 5), and the results showed that eating styles were strongly associated with IBS in both male (tertile 2, OR: 3.09; 95% CI: 1.64–5.84) (tertile 3, OR: 8.50; 95% CI: 4.70–15.38) and female (tertile 2, OR: 1.73; 95% CI: 0.96–3.12) (tertile 3, OR: 2.41; 95% CI: 1.26–4.59) participants; we will demonstrate the relationship between psychological and dietary problems in IBS and sex in future research. Fifth, IBS criteria were self-reported by the participants, which would result in information bias. The related problems in the questionnaire are strictly formulated according to the criteria to improve the accuracy of IBS diagnosis. Furthermore, many researchers use self-reported questionnaires to evaluate IBS, demonstrating the high reliability of the diagnostic results of this method [
56,
57,
58]. Sixth, we cannot identify people with more than one eating style now, but we will work to overcome this challenge in the next step of our research.