Researchers have noticed an association between obesity and certain cancers for some time, but the matter received added attention this week as CDC published data
in Vital Signs
showing that overweight and obesity are now associated with at least 13 types of cancer, which account for 40% of all cancer diagnoses in the United States.
Simultaneously, CDC officials published a viewpoint
calling attention to this public health challenge, which threatens to put even more stress on the healthcare system now that cancers associated with extra pounds are showing up in younger patients. Many of these are cancers of the digestive tract and its organs: adenocarcinoma of the esophagus; cancers of the gastric cardia, colon and rectum, liver, gallbladder, and pancreas; and cancers in the ovaries and the main body of the uterus, the kidney and the thyroid.
As CDC officials covered in a discussion with the press this week, the science points to inflammation and obesity’s effect on the endocrine system. For women, estrogen levels are implicated in blood cancers and endometrial cancer. So far, the current evidence shows that when we lose weight, these inflammatory markers are reduced somewhat—although it’s not clear that weight loss protects people from cancer completely.
What alarms CDC leaders are the numbers. Obesity in the United States has been climbing for more than 50 years, and now we’re seeing the fallout. In the 10 years from 2005 to 2014, more than 630,000 people were diagnosed with a cancer associated with being overweight or obese; these cancers account for 55% of all cancers in women and 24% of all cancers in men.
Over the decade studied, there was a 1.4% annual increase in these 13 cancers among people aged 20 to 49. Among those age 50 to 64, the rise of these same cancers was slower, just a 0.4% increase. And the numbers suggest a tidal wave of cancer is on the way without drastic measures to shrink America’s waistline.
“Nearly half of all cancers in people younger than 65 years were associated with overweight and obesity,” the officials wrote in JAMA.
“Given the time lag between exposure to cancer risk factors and cancer diagnosis, the high prevalence of overweight and obesity among adults, children, and adolescents may forecast additional increases in the incidence of cancers related to overweight and obesity.”
Two in 3 US adults weigh more than they should, CDC says. Health policy already has the pieces in place to tackle the problem, as the US Preventive Services Task Force calls for screening for obesity and intensive behavioral health interventions for those who qualify, done in 12 to 16 visits for adults and 26 or more visits for children and teens.
The problem, the officials write, is that too few primary care physicians follow the recommendations: only about half regularly assess body mass index, and the Medicare benefit for these interventions is not widely used.
Leaving it all up to primary care physicians won’t work, the authors say. “Because few primary care clinicians are trained in behavior change strategies like cognitive behavioral therapy or motivational interviewing, other trained healthcare professionals, such as nurses, pharmacists, psychologists, and dietitians could assist by providing counseling and appropriate referrals and help people manage their own health,” they wrote.
CDC, meanwhile, calls on states, businesses, and civic leaders to take up the cause at the community level—by promoting healthy eating and creating opportunities for people to be more physically active.
During this week’s session, officials were asked: does obesity cause cancer? Anne Schuchat, MD, RADM, USPHS, the principal deputy director of CDC, explained that “It’s not exactly the same as what we say about tobacco and cancer. But the mounting evidence points to this association and the trends that we’re seeing are an indirect emphasis that there are important general changes going on.”
1. Steele CB, Thomas CC, Henley SJ, et al. Vital Signs: Trends in Incidence of Cancers Associated with Overweight and Obesity — United States, 2005–2014. MMWR.
2. Massetti GM, Dietz WH, Richardson LC. Excessive weight gain, obesity, and cancer: opportunities for clinical intervention [published online October 3, 2017]. JAMA;