A review of several studies published today in the New England Journal of Medicine found new associations between obesity the development of eight additional cancers, in addition to others previously known.
Researchers from the World Health Organization’s International Agency for Research on Cancer (IARC) looked at more than 1,000 epidemiological studies and found that "excess body fatness" is also linked to the risk of developing gastric, liver, gallbladder, pancreatic, ovarian, thyroid, blood (multiple myeloma) and brain (meningioma) cancers.
"I think the main takeaway point is that your health and specifically your body fatness is an important factor for many types of cancer," Dr. Richard Lee, Medical Director of the Integrative and Supportive Oncology Program at the University Hospitals Seidman Cancer Center, told ABC News.
"Patients should understand that they can decrease the risk for developing cancer and improving overall survivorship," by keeping their weight below obesity thresholds, he said. This information can help doctors advising patients on cancer risk, he added.
Researchers in this study also attempted to quantify the risk for obese people to develop this variety of cancers. They found obese people had 1.8 times the risk for developing liver cancer, 4.8 times as high for esophageal adenocarcinoma, and 7.1 times as high for uterine cancer. They also confirmed that for some of these cancers, as your weight goes up, so does the risk.
People may not always connect being overweight to cancer risk in the manner they associate drinking or smoking with increased risk of cancer, Lee noted.
"The public hasn't been educated enough that it is a significant risk factor," he said. "I see patients who are interested in ways they can reduce overall cancer [risk]. I always tell them the first place to start is nutrition and exercise and physical fitness."
This is one of the most comprehensive studies on cancer and obesity to date, according to Dr. Xiao Ou Shu, Associate Director for Global Health at the Vanderbilt-Ingram Cancer Center. He believes it could help educate the public that being overweight isn't only about cardiac problems.
"I think that the public has been informed about the potential risk for cancer associated with obesity, but there has been much more information disseminated about cardiovascular disease risk than cancer risk," Ou Shu told ABC News.
One positive discovery from this study the authors found is that obese people who lose weight appear to reduce their cancer risk.
"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," Graham Colditz, MD, Dr PH and deputy director of the School of Public Health at Washington University School of Medicine in St. Louis, who chaired the IARC Working Group, said in a statement. "Public health efforts to combat cancer should focus on these things that people have some control over."
Dr. Kavita Vakharia, of the ABC News Medical Unit, contributed to this report.