THURSDAY, Oct. 11 (HealthDay News) -- Obese people are six times more likely to develop esophageal cancer than people with healthy weight, says an Australian study that looked at 800 people with esophageal tumors and 1,600 people without the disease.

People with a body mass index (BMI) of 40 or more were six times as likely to have esophageal cancer as those with a BMI between 18.5 and 25 (a BMI of 30 is considered the threshold for obesity).

According to a team from the Queensland Institute of Medical Research in Brisbane, the finding held true even after accounting for other factors known to be linked to the disease, such as high alcohol consumption and smoking.

This suggests that obesity is an independent risk factor for esophageal cancer, said the study authors, who explained that higher levels of fat tissue in the body increase insulin production. This, in turn, boosts levels of circulating insulin-like growth factor.

Both these hormones stimulate cell growth and inhibit cell death -- conditions that can lead to cancer development, the team said.

The researchers also noted that fat cells produce hormones called adipocytokines that speed up cell growth and play a role in inflammatory processes.

Repeated symptoms of severe heartburn or gastrointestinal reflux disease were also associated with a much higher risk of esophageal cancer, the researchers said. The more frequent the symptoms, the greater the risk. Gastrointestinal reflux disease quintupled the risk of esophageal cancer, while a combination of acid reflux and obesity increased the risk by a factor of 16.

The study was published Oct. 11 in the online edition of the journal Gut.

More information

The American Cancer Society has more about esophageal cancer.