New Clues: Obesity and Osteoarthritis
Highlight from ObesityWeek 2015
Commentary by Steven Heymsfield, MD; Stephen Messier, PhD; and Timothy Griffin, PhD
Obesity is a long-known major risk factor for osteoarthritis (OA). Now, scientists are uncovering new information about just how risky excess weight is for joints. They're also discovering other mechanisms besides obesity that may drive risk, according to research presented at ObesityWeek 2015 in Los Angeles.
Overview of the Obesity-Osteoarthritis Link
Among people with a body mass index (BMI) of 35 to 40, ''osteoarthritis is almost universal," said Steven Heymsfield, MD, professor in the Metabolism-Body Composition Lab at Pennington Biomedical Research Center in Baton Rouge. Women are affected more than men, but the hallmark symptoms are the same for both genders, he said—stiffness in the morning typically lasting less than 30 minutes and mobility problems. "There's a silent phase of the disease," he said, and it’s often many years before symptoms become apparent.
As the number of people with obesity has risen, so has OA, and that's not coincidence, according to Stephen Messier, PhD, professor and director of the J.B. Snow Biomechanics Laboratory, Wake Forest University, Winston-Salem, N.C. "The increase in the prevalence of OA is directly attributable to the rise in obesity," Dr. Messier said. "Severely obese women are 17 times as likely to have knee OA as normal-weight women.”
“Beside obesity, genetics play a role in osteoarthritis,” Dr. Heymsfield said. "Over 80 gene mutations have been identified that may lead to this. There's a high concordance in twin studies on OA. So there are very clearly genetic factors involved.''
“Research has shown that metabolic inflammation also has a direct effect on OA independent of excess weight effects,” Dr. Heymsfield said. The chondrocyte cell that produces cartilage is directly impacted by the inflammatory processes. “Inflammation of the joint contributes to the inflammation already present in obesity,” he said.
Despite some debate about which the contributions of various mechanisms, one fact is clear, "Obesity accelerates the onset of knee OA by about 20 years. So obese individuals are more likely to live with this for a longer period of time,” said Timothy Griffin, PhD. Dr. Griffin is associate member, Aging & Metabolism Research Program, Oklahoma Medical Research Foundation, who has found inflammatory markers linked with the development of OA.
Intensive Diet and Exercise for Arthritis (IDEA) Trial
Obese patients can do more than live with pain; experts agree. Messier looked at the optimal combination (diet, exercise, both) to produce weight loss and reduce knee pain related to osteoarthritis. The goal, he said, “is to reduce the load on the knees by reducing weight, delaying or eliminating the need for total knee replacement.”
Mean age of the 399 participants was 66-years in the 18-month study. The comparators in the IDEA trial were intensive diet-only weight loss, diet and exercise weight loss, and exercise-only weight loss. Participants were told to reduce their daily calorie totals by 800-1000 kilocalories/day (kcal). They did so by consuming meal replacements for two meals and keeping the third meal to 500-750 kcal/day. Exercise included two 15-minute walking periods followed by 20-minute weight training sessions three times a week. Participants met weekly with program leaders for six months, then biweekly for the remainder of the study period.2
- For weight loss and pain reduction, the combination group (diet + exercise) was superior: 11.4% weight loss.
- The diet-only group averaged 9.5% weight loss.
- The exercise-only group average 2% weight loss
“Half of the diet and exercise group reached the 10% weight loss goal,” Dr. Messier said.2
While each group experienced reduced knee pain, the diet plus exercise group reported the improved function. Dr. Messier said, "Ten percent [weight loss] is the magic number." Inflammation was reduced in both diet groups.
Dr. Messier’s suggested physicians tell their patients who are overweight or obese, "You can reduce your pain by 50% and improve your mobility and functioning with long-term intensive diet and moderate exercise." Patients with osteoarthritis are capable of more intense exercise than traditionally believed, Dr. Messier said.
November 10, 2015