Research is still lacking to support a link between obesity and an increased risk of developing all types of cancer. Nevertheless, a review1 of more than 1,000 epidemiologic studies by the International Agency for Research on Cancer (IARC), a division of the World Health Organization, examining the preventive effects of weight control on cancer risk has found strong evidence that being overweight or obese increases the risk of developing at least 13 types of cancer. The cancer types include esophageal, gastric cardia, colorectal, liver, gallbladder, pancreatic, uterine, kidney, ovarian, meningioma, thyroid, and postmenopausal breast cancers, as well as multiple myeloma.
According to Graham A. Colditz, MD, DrPH, MPH, Associate Director of Prevention and Control at the Alvin J. Siteman Cancer Center, Washington University School of Medicine, St. Louis, Missouri, and Chair of the IARC working group, taken together, these malignancies account for 20% of all new cancer diagnoses, making obesity the second greatest environmental risk factor for developing cancer after smoking.