Obese people are six times as likely to develop gullet (oesophageal) cancer as people of 'healthy' weight, shows research published ahead of print in the journal Gut.
Rates of oesophageal cancer have been rising rapidly, and in some countries, they have risen faster than those of every other major cancer, say the authors.
The findings are based on a comparison of almost 800 people with oesophageal cancer and almost 1600 randomly selected people eligible to vote, who did not have the disease.
Men and those under the age of 50 were especially vulnerable, the findings showed.
The link between acid reflux and gullet cancer is well known, and unsurprisingly, repeated symptoms of severe heartburn or gastrointestinal reflux disease (GORD) were associated with a much higher risk of the cancer.
And the more frequent the symptoms, the greater was the likelihood of having oesophageal cancer.
GORD quintupled the risk of oesophageal cancer, and a combination of obesity and acid reflux boosted the chances of having it by a factor of 16.
But people who were clinically obese had a much higher risk of oesophageal cancer than those whose weight was in the healthy range, regardless of whether they had reflux disease or not.
Those with a body mass index (BMI) of 40 or more were six times as likely to have the cancer as those with a BMI between 18.5 and 25.
This finding held true even after taking account of other factors known to be implicated in the disease, such as smoking and high alcohol consumption.
This suggests that obesity is an independent risk factor for the disease, say the authors.
Higher levels of fat tissue in the body boost insulin production, which in turn increases the amount of circulating insulin-like growth factor.
Both these hormones stimulate cell growth and curb cell death, conditions which favour the development of cancers, explain the authors.
Fat cells also produce other hormones, collectively known as adipocytokines, which speed up cell growth and are involved in inflammatory processes in the body, they say.
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