But the findings do not prove excess weight causes these cancers. It is difficult to isolate the effects of obesity, per se, since it often goes hand-in-hand with lifestyle habits and medical conditions that have also been linked to cancer. A body of research supports the idea that excess weight itself influences cancer development.
The cancer society says excess weight contributes to as many as 20 percent of all cancer deaths. “This study is interesting because it suggests that the number of years you spend being overweight also matters,” said Gapstur, who was not involved in the research. And that, she said, should provide further incentive to avoid excess weight gain in the first place.
Currently, about 7 out of 10 adults in the United States are overweight, and more than one-third are obese , according to background notes with the study.
The bottom line, Gapstur said, is simple: “Try to maintain a healthy weight throughout adulthood.”
Malina Arnold of the International Agency for Research on Cancer agreed. “Having a healthy body weight is always beneficial -- not only to prevent cancer, but also other diseases associated with [excess weight],” she said.
The study appears in the Aug. 16, 2016 issue of the online journal PLOS Medicine, "Women's risk for 4 cancers goes up the more years spent overweight," by Amy Norton, CBS News, August 17, 2016)