Although the number of new cancer diagnoses in the U.S. declined between 1999 and 2008, the rate of several cancers linked to obesity and sedentary lifestyle increased each year during that period, according to a report in Cancer.
The report found that the rate of cancer declined by 0.6% annually between 2004 and 2008, while the rate of cancer among women declined by 0.5% between 1998 and 2006. Most of the declines in cancer rates were seen among lung, breast, colon, and prostate cancers.
However, the rate of esophageal, kidney, pancreatic, liver, endometrial, and thyroid cancers all increased during that time, which researchers largely attributed to the increase in obesity rates and inactivity. The report found excess weight and sedentary lifestyle can be a risk factor for between 25% and 33% of common cancers in the United States.
Researchers reviewed more than 7,000 studies and found an association between excess weight and several cancers. Although it is unclear what the precise link is, researchers say fat cells may promote production of more insulin or hormones that can stimulate tumor growth. The study also found that obesity can lower the quality of life for cancer survivors and worsen the prognosis for many cancers.
Not all obesity-related cancers increased during the study period, however. Rates of colorectal cancer declined by 2.6% annually, largely because of widespread screening (McKay, Wall Street Journal, 3/28; Lloyd, USA Today, 3/28; Reinberg, HealthDay, 3/28).