Dr. Li added, “The distribution of fat also plays a role — the higher the waist to hip ratio, the greater the risk.” She found that cancer risk was greater the earlier in life a person becomes obese, and survival time was shorter among those who were still obese when the cancer was diagnosed.

Obesity is also the leading risk factor for the development of Type 2 diabetes, in which the body resists the action of insulin, prompting the pancreas to produce more and more of this hormone. Insulin promotes cell growth, providing a link between diabetes and the development of pancreatic cancer.

However, the relationship is complicated, to say the least. In a 2011 report in Molecular Carcinogenesis, Dr. Li noted that “diabetes or impaired glucose tolerance is present in 50 to 80 percent of patients with pancreatic cancer.” She said, “Diabetes is both a cause and consequence of cancer,” although which comes first — diabetes or cancer in the organ that controls blood glucose — is not crystal clear.

A European study of more than 800,000 people with Type 2 diabetes found this disease is sometimes an early sign of an otherwise hidden pancreatic cancer.

In studies at the Mayo Clinic, elevated glucose levels, a condition called pre-diabetes, were detected in some patients two years before pancreatic cancer was diagnosed. In these patients, Dr. Li explained, diabetes is actually a symptom of the hidden cancer. It is a type of diabetes called 3C, caused by a diseased or damaged pancreas, and medical researchers are now looking for ways for doctors to readily distinguish between Type 3C and Type 2 diabetes.

The lag time between the development of diabetes and diagnosis of cancer is a potential window of opportunity that may enable cancer detection at an early, curable stage, Dr. Li said.

If a biomarker for the cancer was identified, it may be possible to find cancer in these patients when the tumor is too small to be seen on a scan and before symptoms develop. For example, an antibody might be used that targets a molecule on small tumors.