Diet, food, and reflux

The major pathophysiologic abnormality in GERD is dysfunction of the lower esophageal sphincter (LES), either manifest as a low resting pressure, or due to a spontaneous decrease in LES pressure due to sphincter shortening in response to gastric distention, a so called transient lower esophageal sphincter relaxation (TLESR). Variability in basal or resting LES pressure and frequency of TLESR makes understanding the effect of food and meal composition on GERD, complex. LES pressure in normals is decreased by fat, which also increases the frequency of TLESR’s. This potentially will predispose to increase in GERD symptoms. TLESR frequency is increased by distension of the gastric fundus, so any meal, regardless of its composition will have the potential to promote reflux. It is also clear that there is a relationship between the speed at which one eats and postprandial reflux. A meal eaten in less than 5 minutes results in more postprandial reflux than a meals eaten over 30 minutes.

There are few studies on LES function in the obese. The limited data suggests that basal pressure in the morbidly obese is similar to those of ideal body weight. Hiatal hernia is more often seen in patients with obesity and the authors’ clinical impression is that they tend to be larger in the obese. The relationship between obesity and esophageal motility function, notably TLESR, has recently been studied in subjects with GERD and hiatus hernia. Obesity is associated with increased TLESR, postprandial gastroesophageal reflux (GER), and esophageal acid exposure. The frequency of TLESR is correlated with increased body mass index (BMI) and waist circumference. The pressure profile within and across the gastroesophageal junction in the obese is altered in a way that increases GER. During inspiration, increased intragastric pressure and the gastroesophageal pressure gradient are correlated with increased BMI. The changes noted above are more strongly correlated with waist circumference. The speculation is that waist circumference is the mediator of the obesity effect on GERD. Obesity is associated with increased axial separation between the LES and the extrinsic crural diaphragm, indicating anatomic disruption of the esophageal junction, which likely contributes in the development of hiatal hernia. These findings offer a physiologic explanation for the effect of obesity on GERD. A rise in intra-abdominal pressure in obesity may cause the cephalad movement of a hiatus hernia, predisposing to reflux. Gastric volume and gastric emptying are normal in the limited studies in obese subjects. One study demonstrated higher maximal gastric acid response to gastrin stimulation —but gastric acid production is probably normal. There is an association between obesity and intraesophageal acid exposure, likely mediated by waist circumference. Acid sensitivity may be increased in the obese compared with those of normal body weight. To summarize these studies: obese subjects are more likely to have a hiatal hernia, increased intragastric pressure, and an augmented gastroesophageal pressure gradient—providing the ideal situation for reflux. Abdominal obesity, specifically a greater waist circumference, is likely the mediator of the effect of increased body weight on gastric pressure. Finally, gastric emptying is delayed after large meals and after high-calorie meals. Accordingly, a large, high-fat meal would predispose to TLESR and a greater risk for reflux ( Table 1 ).

Symptoms

Studies investigating the association of GERD symptoms and obesity are conflicting. A large population study from Sweden did not demonstrate a relationship between BMI and symptoms. A meta-analysis in the United States found a positive association between the presence of GERD and increasing BMI. Other large-scale studies have shown that GERD is common in the general population and especially so among the overweight. A strong positive association between BMI and symptoms of GERD was found in a recent cross-sectional study in a large cohort of women. An increase in BMI of more than 3.5 kg/m ² , as compared with no weight changes, was associated with an increased risk of frequency of GERD symptoms. A BMI over 30 kg/m ² was associated with a three-fold increase in the odds of having frequent reflux symptoms. Weight gain increased risk of symptoms of GERD and weight loss decreased risk. A dose-response relationship between BMI and the risk of reporting symptoms of GERD among both men and women was seen in a recent meta-analysis. A BMI between 25 and 29 kg/m ² and a BMI greater than 30 kg/m ² were associated with an increased risk for GERD symptoms—odds ratios of 1.43 and 1.94 respectively ( P <.001). There was a higher hospitalization rate for reflux codes in patients with an elevated BMI compared with normal-weight controls in a recent cross-sectional study. An increase in BMI is associated with an incremental increase in the risk of developing GERD symptoms. The difference was not as dramatic, but there was a significant statistical trend toward more severe symptoms in the obese—particularly in women—compared with the ideal body weight population.

The Progression of Gastroesophageal Reflux Disease (ProGERD) study (N = 6215), found that a higher BMI was associated with more frequent and more severe heartburn, regurgitation, and erosive esophagitis. The findings were more pronounced for regurgitation than heartburn. Obese women had an increased risk of severe esophagitis compared with women with normal weight (odds ratio 2.51, 95%CI 1.53–4.12). There was, however, no difference evident in men.

Contradictory results have been seen in evaluating esophageal acid exposure in obesity. A small study found 64% of patients in a bariatric surgery program had abnormal ambulatory 24-hour esophageal acid exposure, higher than asymptomatic volunteers ( P = .04). In addition, heartburn, acid regurgitation, dysphagia, and asthma were more prevalent in the bariatric surgery patients than in the general population. Fifty consecutive obese patients referred for bariatric surgery had 24-hour ambulatory pH and endoscopy findings similar to the general population. An additional study found a BMI greater than 30 kg/m ² to be associated with a significant increase in the number of reflux episodes, reflux episodes of less than 5 minutes, and total and percent time with pH less than 4, especially in the postprandial period. Waist circumference was associated with esophageal acid exposure, but was not as significant or consistent as BMI. An independent association between increasing abdominal diameter (independent of BMI) and reflux-type symptoms was seen in whites, but not in blacks or Asians. Perhaps increased obesity may disproportionately increase GERD-type symptoms in whites and in males. Overall, the weight of the epidemiologic evidence supports an association between GERD and obesity.

Symptoms

Studies investigating the association of GERD symptoms and obesity are conflicting. A large population study from Sweden did not demonstrate a relationship between BMI and symptoms. A meta-analysis in the United States found a positive association between the presence of GERD and increasing BMI. Other large-scale studies have shown that GERD is common in the general population and especially so among the overweight. A strong positive association between BMI and symptoms of GERD was found in a recent cross-sectional study in a large cohort of women. An increase in BMI of more than 3.5 kg/m ² , as compared with no weight changes, was associated with an increased risk of frequency of GERD symptoms. A BMI over 30 kg/m ² was associated with a three-fold increase in the odds of having frequent reflux symptoms. Weight gain increased risk of symptoms of GERD and weight loss decreased risk. A dose-response relationship between BMI and the risk of reporting symptoms of GERD among both men and women was seen in a recent meta-analysis. A BMI between 25 and 29 kg/m ² and a BMI greater than 30 kg/m ² were associated with an increased risk for GERD symptoms—odds ratios of 1.43 and 1.94 respectively ( P <.001). There was a higher hospitalization rate for reflux codes in patients with an elevated BMI compared with normal-weight controls in a recent cross-sectional study. An increase in BMI is associated with an incremental increase in the risk of developing GERD symptoms. The difference was not as dramatic, but there was a significant statistical trend toward more severe symptoms in the obese—particularly in women—compared with the ideal body weight population.

The Progression of Gastroesophageal Reflux Disease (ProGERD) study (N = 6215), found that a higher BMI was associated with more frequent and more severe heartburn, regurgitation, and erosive esophagitis. The findings were more pronounced for regurgitation than heartburn. Obese women had an increased risk of severe esophagitis compared with women with normal weight (odds ratio 2.51, 95%CI 1.53–4.12). There was, however, no difference evident in men.

Contradictory results have been seen in evaluating esophageal acid exposure in obesity. A small study found 64% of patients in a bariatric surgery program had abnormal ambulatory 24-hour esophageal acid exposure, higher than asymptomatic volunteers ( P = .04). In addition, heartburn, acid regurgitation, dysphagia, and asthma were more prevalent in the bariatric surgery patients than in the general population. Fifty consecutive obese patients referred for bariatric surgery had 24-hour ambulatory pH and endoscopy findings similar to the general population. An additional study found a BMI greater than 30 kg/m ² to be associated with a significant increase in the number of reflux episodes, reflux episodes of less than 5 minutes, and total and percent time with pH less than 4, especially in the postprandial period. Waist circumference was associated with esophageal acid exposure, but was not as significant or consistent as BMI. An independent association between increasing abdominal diameter (independent of BMI) and reflux-type symptoms was seen in whites, but not in blacks or Asians. Perhaps increased obesity may disproportionately increase GERD-type symptoms in whites and in males. Overall, the weight of the epidemiologic evidence supports an association between GERD and obesity.