by David Gutierrez
The new study was designed as a follow-up to an October report by the World Research Cancer Fund, which concluded that excessive body fat could be a cause of certain cancers.
“This study has extended that further and reported specifically on 20 different types of cancer,” said lead researcher Andrew Renehan. “We showed an association with less common cancers that had not been shown before.”
The researchers conducted an analysis of 144 prior studies that included a total of 282,000 people. They compared the cancer rates of those whose body mass index increased from normal to overweight or from overweight to obese with those whose body mass index remained normal or overweight.
Body mass index is a measurement of weight relative to height, and a commonly used measure of obesity.
An increase in body mass category increased the risk of rare blood cancers in both women and men, including adult leukemia, multiple myeloma and non-Hodgkin’s lymphoma. In men, it increased the risk of colon and kidney cancers by 24 percent and the risk of thyroid cancer by 33 percent.
Women who went from normal to overweight suffered a 34 percent higher risk of kidney cancer and a 59 percent higher risk of gall-bladder cancer.
The researchers speculated that the sex differences in cancer risk arise from the different effects that the hormone changes caused by increased body fat have on women and men.
The relationship between increased obesity and higher cancer risk appeared consistent in North America, Europe and Asia, the researchers said, but they noted that obesity appeared to increase the risk of breast cancer more in Asia than in other parts of the world.