However, since one's body composition can be altered, there is hope to reduce the amount of disability and improve the quality of life of these patients.

The study, led by researchers from Johns Hopkins University School of Medicine, was published in the October issue of Arthritis Care & Research.

The results, based on analysis of almost 200 people with rheumatoid arthritis, found that those with increasing amounts of fat and decreasing amounts of lean mass (skeletal muscle) on the arms and legs had the most increasing disability linked with the highly inflammatory disease of the joints.

The authors theorized that increasing fat may affect the normal range of motion of the arms and legs or that the fat may biochemically interfere with muscular function, but they said the most likely reason is that the fat may be infiltrating the muscles, reducing muscle quality.

"Interestingly, in studies of the general population, increasing fat mass has also been more strongly linked to worsening functional capacity than decreasing lean mass, suggesting that efforts to improve physical function require a focus on fat reduction with at least as much emphasis, if not more, than increasing lean mass," the authors wrote.

"In the absence of interventional trials, these findings suggest that practitioners should encourage muscle strengthening and fat loss in their patients with RA as a method of reducing disability," they concluded.

-- Kevin McKeever