America has nearly 50 million people who are diagnosed with arthritis; the condition is found to be more common among the obese. According to the Center for Disease Control and Prevention, 21 million people say the disease limits their physical activities.

Aging and obesity are the main causes of arthritis. Researchers however expect arthritis to increase significantly over the next 20 years unless Americans implement strict weight control measures in their diets.

It’s expected that the number of adults with arthritis will hit 51.9 million in 2010 and 67 million by 2013.

Arthritis represents a major public health problem in the United States “that can be addressed, at least in part, by implementing proven obesity prevention strategies and increasing availability of effective physical activity programs and self-management education courses in local communities,” research authors write.

Researchers added that the prevalence of arthritis increases significantly with age, and risk factors are affected by weight, physical activity and lifestyle factors such as smoking.

Survey data was collected between 2007 and 2009 on a national phone survey.

Currently more than 67 percent of Americans are either classified as overweight or obese.

Results of the study are published in October 8 issue of Morbidity and Mortality Weekly Report..