We've been told for decades that carrying around extra pounds can make us more likely to develop heart disease and diabetes later in life. But there's a growing understanding that being overweight can also increase our risk of another chronic disease: cancer. And it's not necessarily a "later in life" thing.
Studies have linked excess body fat to about a dozen kinds of cancer. In a new analysis of data from 25 states' cancer registries, researchers found that prevalence of six obesity-related cancers increased in adults under age 50 between the years 1995 and 2004, with steeper rises in the youngest age groups.
"This study is interesting because it points out two different things — one is the obesity tie-in, and the other is that there seems to be more young people getting cancer," explains oncologist Dale Shepard, M.D., who was not involved in the study.
A jump in the number of young people diagnosed with colorectal cancer has been widely reported, but the new study brings attention to other obesity-related cancers that are increasing in young adults -uterine, gallbladder, kidney and pancreatic cancer, and multiple myeloma.
While these cancers are still more common in older adults, the growth in diagnoses of people under 50 is striking.
"Half the obesity-related cancers were increasing in incidence, while most of the other cancers that are not obesity related - like ones that are smoking-related - were actually stable or declining," Shepard notes. "And the youngest people are the ones that have the bigger increases."
Obesity and cancer: How are they related?
The link between the two isn't completely understood, but there are a couple theories as to why extra body fat might contribute to the development of cancer.
"We think inflammation is important," Shepard says. "People who are obese are more likely to have low-grade inflammation, which is associated with cancer risk."
Then there's the hormone factor. Fat cells secrete certain hormones that have been linked to cancer risk.
There are also other factors that contribute to obesity — like whether someone exercises regularly or eats a healthy diet — that may also directly play into cancer risk.
For Shepard, one big takeaway is the need to pay more attention to obesity in young people and encourage those at risk to make changes to their diet, step up their exercise and decrease their sedentary time.
Nearly 40 percent of U.S. adults and over 18 percent of children are obese, according to the latest tally by the Centers for Disease Control and Prevention.
"We spend a lot of time, effort and money coming up with better treatments for cancer — this is important because it suggests a way to decrease the incidence of cancer in the first place," he says. "Minimizing the risk of cancer up front could have far more impact."
A Wellness Update is a magazine devoted to up-to-the minute information on health issues from physicians, major hospitals and clinics, universities and health care agencies across the U.S. Online at www.awellnessupdate.com.