Current estimates of the effect of obesity in increasing the risk for cancer are based on observational studies and may be underestimating the effect. The risk may be twice as large as is currently thought, says a group of international researchers who report a new approach to estimating the risk.
They conducted a systematic analysis of genetic data using a Mendelian randomization (MR) approach.
"The importance of these analyses is that they suggest that the effect of being overweight on cancer risk has been underestimated in the past and that obesity plays an even more important role in cancer than previously suggested," commented coauthor Richard Martin, BMedSci, PhD, professor of clinical epidemiology at the University of Bristol Medical School, United Kingdom, in a statement.
The study was published online July 25 in the International Journal of Epidemiology.
"We compared the genetic MR estimates of the association between BMI [body mass index] and cancer risk with the estimates from classical cohort studies for eight common cancer types that have been linked to obesity," explain corresponding author Paul Brennan, PhD, International Agency for Research on Cancer, Lyon, France, and colleagues.
"[Our] MR-based results [show] the cancer burden explained by elevated BMI for the six cancers [analyzed] would be almost 8% in high-income countries, as opposed to 3% based on previous estimates for these cancers, suggesting that the cancer burden has been substantially underestimated for the majority of obesity-related cancers," they conclude.
