Barretts esophagus
GERD may lead to Barretts esophagus, a type of intestinal metaplasia, which is in turn a precursor condition for esophageal cancer. The risk of progression from Barretts to dysplasia is uncertain, but is estimated at 20% of cases. Due to the risk of chronic heartburn progressing to Barretts, EGD every five years is recommended for people with chronic heartburn, or who take drugs for chronic GERD. Causes
Acid reflux is due to poor closure of the lower esophageal sphincter, which is at the junction between the stomach and the esophagus. Factors that can contribute to GERD:

Hiatal hernia, which increases the likelihood of GERD due to mechanical and motility factors. Obesity: increasing body mass index is associated with more severe GERD. In a large series of 2,000 patients with symptomatic reflux disease, it has been shown that 13% of changes in esophageal acid exposure is attributable to changes in body mass index.Factors that have been linked with GERD, but not conclusively:

Obstructive sleep apnea
Gallstones, which can impede the flow of bile into the duodenum, which can affect the ability to neutralize gastric acidIn 1999, a review of existing studies found that, on average, 40% of GERD patients also had H. pylori infection. The eradication of H. pylori can lead to an increase in acid secretion, leading to the question of whether H. pylori-infected GERD patients are any different than non-infected GERD patients.
Middle aged adults with low birth weight present with a higher chance of obesity and diabetes. Children that are born under six pounds were 1.27 times more likely to develop diabetes compared to babies born at a healthy weight over six pounds. Growth hormone (GH) therapy at a certain dose induced catch-up of lean body mass (LBM). However percentage body fat decreased in the GH-treated subjects. Bone mineral density SDS measured by DEXA increased significantly in the GH-treated group compared to the untreated subjects, though there is much debate over whether or not SGA (small for gestational age) is significantly adverse to children to warrant inducing catch-up. Babies that have a low birth weight are thought to have an increased risk of developing type 2 diabetes in later life. Low birth weight is linked with increase rates of obesity, insulin resistance, and type 2 diabetes and it is shown that children with the low birth weights have increased leptin levels after they catch up growth during childhood. Adiponectin levels are positively related with birth weight and BMI in babies with an increase of risk of type 2 diabetes. The leptin and adiponection mechanisms are still being studied when involving low birth weight. Around the world
There is much variation regarding birth weight within continents, countries, and cities. Even though over 20 million babies are born each year with low birth weight, it is hard to know the exact number as more than half of babies born in the world are not weighed at birth.