**2. GERD in obesity**

Obesity has reached an epidemic proportion globally [11]. This condition is diagnosed when the measured body mass index (BMI) is ≥30 kg/m2 and further classified into three group based on its severity levels: class I (BMI 30.0–34.9), class II (BMI 35.0–39.9), and class III (BMI ≥40.0) [11]. Epidemiological study have shown that obesity is a major risk factor for GERD and, consequently, has accounted for the increasing prevalence of GERD, worldwide [12]. Study by Hampel *et al.* showed overweight and obesity fulfill a number criteria for a causal relationship with GERD [9]. Previous studies also discovered the influence of BMI on GERD was not affected by nutritional intake [13–15].

Study by Murray *et al*. showed that subjects with obesity reported more frequent heartburn compared to the subjects with normal weight (OR 2.91) and this obese subjects also showed significant association with severe heartburn (OR 1.19) [13]. A dose–response relationship between frequency of heartburn or regurgitation and high BMI was observed by El-Serag *et al*. [16]. This study also found subjects with mucosal erosion were more often to be overweight or obese, compared to subjects without erosion [16].
