Scientists at Duke University Medical Center said the findings of their research suggested excess weight alone isn't what causes the aches and pains of osteoarthritis, despite a long-held notion that carrying extra pounds strains the joints and leads to the inflammatory condition.
"What's surprising is that exercise, without substantial weight loss, can be beneficial to the joints," senior author Farshid Guilak, a professor of orthopedic surgery at Duke, said in a statement. "Ideally, it would be best to be fit and lose a little weight, but this shows that exercise alone can improve the health of your joints."
Using two sets of male mice -- half fed a high-fat diet and the other given regular feed -- researchers noted significant differences among the two groups. Mice on the high-fat food gained weight rapidly, processed glucose poorly and had much higher blood levels of molecules that trigger the chronic inflammation associated with osteoarthritis, but when those mice got regular exercise, many of the harmful effects diminished -- even though they shed no weight, Guilak said.
The study, published in the journal Arthritis & Rheumatism, found glucose tolerance improved, while the inflammatory response was disrupted among key signaling molecules called cytokines -- easing the development of arthritis.
If the extra weight on the joints had been the cause of the arthritis, the researchers noted, exercise would have exacerbated the problem, but it helped.
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