The knee joint is a common site of osteoarthritis -- a degenerative joint disease that affects more than a third of adults over the age of 60 -- and in many people the condition progresses until total knee replacement becomes necessary.
"Once the cartilage is lost in osteoarthritis, the disease cannot be reversed," said lead author Alexandra Gersing, from the University of California-San Francisco.
Weight loss has been shown to slow down cartilage degeneration in overweight and obese individuals, but it was unclear if the method used to lose weight made a difference.
For the study, presented at the 103rd Scientific Assembly and Annual Meeting of Radiological Society of North America in Chicago, the team investigated cartilage degeneration and joint abnormalities over the course of 96 months in 380 overweight men and women.
The participants either had mild to moderate osteoarthritis or risk factors for the disease and were divided into a group of 380 patients who lost weight through diet and exercise, diet alone and exercise alone.
Cartilage degeneration was significantly lower among people who lost weight through diet and exercise or diet alone.
Weight loss through exercise alone showed no significant difference in cartilage degeneration, the researchers said.
"These results add to the hypothesis that solely exercise as a regimen in order to lose weight in overweight and obese adults may not be as beneficial to the knee joint as weight loss regimens involving diet," Gersing said.