Obesity linked to pancreatic cancer

Pancreatic cancer strikes obese and sedentary people more frequently than it does thin individuals and those who exercise regularly, a new study finds. The work suggests that some cases of this deadly disease might be avoided by lifestyle changes.

Researchers identified 350 pancreatic cancer patients among a pool of more than 150,000 people who had filled out questionnaires in the 1970s that provided health and lifestyle data.

The researchers had compiled the original data before any participants developed cancer. The scientists later compared the 350 people who eventually developed pancreatic cancer with study participants of similar age and lifestyle who didn’t.

The data show that although the overall risk of pancreatic cancer is small, obese people faced a 72 percent greater chance of developing pancreatic cancer than did trim people. The team, led by researchers at the Harvard School of Public Health in Boston, accounted for smoking and other lifestyle choices that might bias results. The study appears in the Aug. 22/29 Journal of the American Medical Association.

The pancreas produces insulin, which cells need to process sugars.

Obese people are often insulin resistant–their cells fail to use the hormone efficiently, leaving an excess of insulin in the blood.

Overexposure to insulin in the pancreas could somehow increase the risk of cancer there, says study coauthor Dominique S. Michaud, an epidemiologist currently at the National Cancer Institute in Bethesda, Md.

Exercise, even in moderate amounts, improves sugar metabolism. People who had exercised regularly–by walking or hiking 4 hours per week–faced only half the risk of pancreatic cancer as did those who didn’t exercise at all, the researchers found.

The frequency and size of meals also seems to affect risk. People who ate only one major meal per day and ate smaller amounts throughout the day faced about half the risk of pancreatic cancer as did people who ate three major meals per day.

In an editorial accompanying the new study, Susan M. Gapstur and Peter Gann of Northwestern University Medical School in Chicago say the findings suggest that some pancreatic cancers might be preventable. Obesity and inactivity “could account for as much as 15 percent of pancreatic cancer cases beyond those attributable to smoking,” they say.