Obesity associated with 40 percent of cancers, new data shows

As the rate of overweight and obese Americans continues to rise, new data show that cancers associated with excess weight-which accounted for 40 percent of all cancers diagnosed in the U.S. in 2014-have also risen, according to the Centers for Disease Control and Prevention.

Thirteen common cancers are associated with being overweight or obese, including thyroid, ovarian, pancreatic and breast in post-menopausal women, among others.

Between 2005 and 2017, the rate of cancers not associated with weight went down by 13 percent, while those that are associated went up by 7 percent.

The CDC's report, released this month, confirms what oncologists have already known: In most cases, cancer has more to do with lifestyle and environmental factors than genes and family history. Only about 5 to 10 percent of cancers are hereditary.

Dr. Jaime Bohl, a colorectal surgeon specializing in colon cancer with VCU Massey Cancer Center, explained that excess body weight can cause chronic inflammation. Typically, when there is inflammation, the body works to protect itself, but sometimes that response, especially when prolonged due to chronic inflammation, can lead to the development of cancerous cells.

That means that being overweight or obese over a long period of time especially increases cancer risk. But it also means that any improvement-even just losing 10 pounds for someone who is overweight or obese-can markedly improve health."Every little bit of weight loss and health behavior increases their health and decreases their risk," Bohl said.

While the new information from the CDC can be unsettling for many-about 2 out of 3 adults in the U.S. were overweight or obese between 2013 and 2014-it also means that individuals have more power and control when it comes to their health than many assume.

Bohl cautioned against setting big goals, like those that are often embarked upon as a New Year's resolution. Big changes to lifestyle and behavior are often short-lived and can cause the patient to turn around and gain the weight again soon after hitting their goal.

It's the small steps toward healthy behaviors and lifestyles, she said, that can make the biggest improvement. Daily behavior over time adds up to the largest aggregate benefit. She cautioned against choosing a "goal weight" or focusing on an arbitrary number, because that goes against the primary point of weight loss: to get healthy.

She also encouraged people to pursue routine exams and screenings to lower their risk of cancer. Colorectal cancer is associated with excess body weight, but its rates decreased 23 percent between 2005 and 2014 due to screenings and doctors finding abnormal growths in the colon before they progress to cancer.

Some risk factors can change, others cannot, Bohl said. "Patients cannot change their family history or genetics," she said. "But lifestyle factors change our risk of cancer. Diet, nutrition, exercise-these are modifiable factors."