Smoking weakens the LES and is a strong risk factor for GERD.^{2, 3, 4} A study of infants with GERD found that exposure to cigarette smoke in the environment is associated with reflux, leading the authors conclude that secondhand smoke contributes directly to GERD in infants.⁵ No similar studies on environmental smoke have been done with adults. Psychological stress and alcohol have also been shown to be associated with the weakening of the LES and symptoms of GERD.^{6, 7, 8, 9}

A number of studies have found that obesity increases the risk of GERD,^{10, 11} though one study found no association between severe obesity and GERD.¹² Obese people tend to have weaker sphincters,¹³ and they more often develop a condition related to GERD called hiatal hernia, in which the upper part of the stomach protrudes above the diaphragm, resulting in a deformed LES.¹⁴ It has been suggested that obesity may contribute to GERD by increasing abdominal pressure, but this mechanism has not been proven.¹⁵ The benefit of weight loss for obese patients with GERD is controversial. Some researchers have found that symptoms of GERD are reduced with weight loss,¹⁶ while others have seen no change with weight loss and even increased symptoms in patients with massive weight loss.¹⁷

Lying down prevents gravity from keeping the stomach contents well below the opening from the esophagus. For this reason, many authorities recommend that people with GERD avoid lying down sooner than three hours after a meal, and suggest elevating the head of the bed to prevent symptoms during sleep.^{18, 19, 20}

GERD occurs more frequently during exercise than at rest, and can be a cause of chest pain or abdominal pain during exertion.²¹ One study found that increased intensity of exercise resulted in increased reflux in both trained athletes and untrained people.²² In another study, running produced more reflux than less jarring activities, such as bicycling, while weight training produced few reflux symptoms.²³ Eating just before exercise has been found to further aggravate GERD.^{24, 25} On the other hand, a recent survey found that people who participate in little recreational activity were more likely than active people to be hospitalized for GERD.²⁶ It makes sense for people with GERD to use exercise as part of a healthy lifestyle, perhaps choosing activities that are less likely to cause reflux symptoms.