People who are obese have a greater risk of developing and dying from several types of cancer including malignancies of the breast, ovary, kidney, pancreas, colon, rectum and bone marrow, a research review confirms. Cancer is a leading cause of death worldwide, and the prevalence of obesity has more than doubled over the past generation. Even though excess weight is thought to influence the odds of developing and dying from a wide variety of tumors, the study found “strong evidence” supporting this connection for just 11 cancers. “Other associations could also be genuine, but there is still substantial uncertainty about them,” lead study author Dr. Maria Kyrgiou of Imperial College London said by email.

Globally, 1.9 billion adults are overweight or obese, according to the World Health Organization. Roughly four in ten adults are overweight, and more than one in ten are obese, a condition that increases the risk of heart disease, diabetes, kidney problems and joint disorders in addition to certain cancers. For the current study, researchers analyzed results from 204 previously published studies exploring the connection between obesity, weight gain, waist circumference and 36 different cancers. Researchers looked in particular for evidence that the previous results might have exaggerated the link between obesity and cancer or found a connection that was too small to rule out the possibility that it was due to chance. They found the strongest links were between obesity and malignancies of the digestive organs and for hormone-related tumors in women, according to the report in The BMJ. More research is needed that assesses changes in body fat over time to better understand how obesity directly influences the risk of getting cancer or dying from the disease, the authors conclude. The way obesity impacts the risk of cancer also varies in different parts of the body, Dr. Graham Colditz, a researcher at Washington University School of Medicine in St. Louis, said by email. But the take-home message is the same for every patient, added Colditz, author of an editorial accompanying the study. “Avoiding weight gain through adult years is important,” Colditz said. “Even if you are overweight focus first on not gaining any more weight; for those who are overweight or obese taking off some pounds can lower cancer risk.”