Diabetes mellitus and elevated postload plasma glucose levels have been associated with an increased risk of pancreatic cancer in previous studies.
By virtue of their influence on insulin resistance, it has therefore been hypothesized that obesity and physical inactivity may also increase the risk of pancreatic cancer.
A huge US study has now examined the relationship between pancreatic cancer risk and obesity, height, and physical activity.
The research used data from two US cohort studies conducted by mailed questionnaire.
These were the Health Professionals Follow-up Study (initiated in 1986) and the Nurse's Health Study (initiated in 1976), with 10 to 20 years of follow-up.
| Obesity increases risk of pancreatic cancer|
|Journal of the American Medical Association|
More than 160,000 participants were involved in the study, including 46,648 men, aged between 40 and 75 years, and 117, 041 women, aged 30 to 55 years.
All those enrolled in the study were free of cancer at baseline and had complete data on height and weight.
During follow-up, 350 incident pancreatic cancer cases were documented.
Individuals with a body mass index (BMI) of at least 30 kg/m2 were found to have an elevated risk of pancreatic cancer compared to those with a BMI of less than 23 kg/m2.
Height was also associated with an increased risk of pancreatic cancer.
The research found that physical activity seemed to make no difference to the risk of cancer among people who were not overweight.
However, amongst people who were considered overweight or obese (BMI of at least 25 kg/m2) there was an inverse relationship between total physical activity and pancreatic cancer risk.
The researchers, led by Dr Dominique Michaud, of the Harvard School of Public Health, Boston, USA, write that the findings show "obesity significantly increased the risk of pancreatic cancer."
They add, "Physical activity appears to decrease the risk of pancreatic cancer, especially among those who are overweight."
Writing in the same journal, Dr Susan Gapstur and Dr Peter Gann, of Northwestern University Medical School, Chicago, USA, say the findings are the latest to show that a healthy lifestyle can reduce the risk of pancreatic cancer.
"It is both surprising and gratifying that pancreatic cancer should be emerging as a form of cancer that might be preventable, at least in part through modification of lifestyle habits such as diet, exercise, and smoking," they write.