“We have not had a randomized controlled trial of weight loss among people at risk for cancer who don’t yet have the disease, where we can show that weight loss reduces the risk for cancer. And we never will,” Rachel Ballard-Barbash, MD, MPH, told The ASCO Post.

“We know from a number of very large trials, such as the Women’s Health Initiative, that we need a very large sample of people to test that association, because cancer is still a rare condition compared to heart disease, high blood pressure, or diabetes,” she said. “If we put people just at risk for cancer on a weight loss intervention, they would first show improvements in conditions like diabetes, heart disease, and hypertension, and the trial would have to be stopped before we would actually get the answer for cancer. Once you demonstrate a significant benefit for the overall population in some other disease endpoint, it is no longer ethical to continue such a trial.”

Dr. Ballard-Barbash is Associate Director of the Applied Research Program, Division of Cancer Control and Population Science, at the National Cancer Institute. ■