The review, by Maria Kyrgiou and colleagues, collected and analyzed over 200 systemic reviews and meta-analyses that included data on 36 different cancers. Of these, the researchers found strong links between various measures of overweight and an increased risk of cancers of the esophagus (adenocarcinoma), stomach, colon, rectum, biliary tract, pancreas, breast, endometrium, ovary, and kidney, as well as multiple myeloma.
In their editorial, Park and Colditz, point out key differences between the conclusions of the umbrella review and a 2016 International Agency for Research on Cancer (IARC) report, which Colditz headed, and which concluded that there is sufficient evidence that overweight and obesity increased the risk of 13 types of cancer. Differences between the findings of the two papers, Park and Colditz write, could be related to differences in the type of studies included in the analyses and the methods used to assess the studies that were included. Among other things, the:
"IARC report clearly demonstrated the importance of assessing the quality of each meta-analysis, including search strategy, inclusion and exclusion criteria, and data extraction, which is often outside the scope of an umbrella review"Despite some important differences between the IARC report and umbrella review, the findings of the new review further bolster the evidence that overweight and obesity cause cancer. As Park and Colditz write:
"Though some specifics remain to be worked out, the unavoidable conclusion from these data is that preventing excess adult weight gain can reduce the risk of cancer."The American Institute for Cancer Research estimates that overweight and obesity cause over 130,000 cancers each year in the United States, and millions annually lose their lives to weigh-related cancers worldwide. As the obesity epidemic continues largely unabated, the tragedy of these numbers will only worsen if we stay on the same course. Among other efforts to address the issue, Park and Colditz conclude, we need to tap the currently unmet potential of the healthcare system:
"Given the critical role of healthcare providers in obesity screening and prevention, clinicians, particularly those in primary care, can be a powerful force to lower the burden of obesity related cancers, as well as the many other chronic diseases linked to obesity such as diabetes, heart disease, and stroke. The data are clear. The time for action is now."