The study, published in the journal Gut, suggested obesity is an independent risk factor for developing esophageal cancer, which is the fastest rising cancer in some countries.

Researchers at Queensland Institute of Medical Research and University of Queensland, both in Brisbane, compared 800 people with esophageal cancer and almost 1,600 randomly selected people eligible to vote, who didn't have the disease. The researchers found those with a body mass index of 40 or more were six times as likely to have the cancer as those with a BMI between 18.5 and 25, regardless of whether they had reflux disease or not.

The link between esophageal cancer and reflux disease -- repeated severe heartburn or gastrointestinal reflux disease -- has already established. This study found gastrointestinal reflux disease quintupled the risk of esophageal cancer, but a combination of obesity and acid reflex boosted the chances of having it by a factor of 16.