Being overweight may increase risk of 8 cancers

Maintaining a healthy body weight could help ward off even more types of cancer than researchers previously thought. A study published Thursday in The New England Journal of Medicine found excess weight was linked to eight additional types of cancer— stomach, liver, gall bladder, pancreas, ovary, the brain tumor meningioma, thyroid cancer and multiple myeloma— after reviewing more than 1,000 related studies.

Research in 2002 by the same team, led by study author Dr. Graham Colditz, under the the World Health Organization’s (WHO) International Agency for Research on Cancer (IARC), drew a link between excess weight and a higher risk of colon, esophagus, kidney, breast and uterus cancer.

"The burden of cancer due to being overweight or obese is more extensive than what has been assumed," Colditz, deputy director for the Institute for Public Health at Washington University School of Medicine in St. Louis, said in a news release. "Many of the newly identified cancers linked to excess weight haven't been on people's radar screens as having a weight component."

While previous studies have found obesity can increase the chances of developing health issues like diabetes and heart disease, which can also raise the risk of early death, study authors noted excess weight can specifically drive cancer growth by promoting inflammation. Being overweight or obese leads to an overproduction of estrogen, testosterone and insulin, which can further fuel the progression of cancer.

Researchers observed that the higher a person’s body mass index (BMI), the greater his or her cancer risk was. According to the National Institutes of Health, for adult men and women, a BMI between 18.5 and 24.9 indicates a healthy weight. Overweight is defined as a BMI between 25 and 29.9, and a BMI of 30 or higher indicates obesity.

In the study, the cancer risk-BMI trend was similar among men and women, and remained consistent across North America, Europe, Asia and the Middle East when data were available, according to the release.

"Lifestyle factors such as eating a healthy diet, maintaining a healthy weight and exercising, in addition to not smoking, can have a significant impact on reducing cancer risk," Colditz said in the release. "Public health efforts to combat cancer should focus on these things that people have some control over."

For those individuals who have trouble shedding pounds, avoiding more weight gain may help, he added.

"Significant numbers of the U.S. and the world's population are overweight," Colditz said in the release. "This is another wake-up call. It's time to take our health and our diets seriously."