BARCELONA – Dramatic weight loss favorably alters mechanical and inflammatory mechanisms that are part of the osteoarthritis disease pathway, according to 18-month findings from a prospective, single-line randomized controlled trial.
Weight loss appears to reduce knee joint compressive loads and the inflammatory markers interleukin-6 (IL-6) and leptin, explained Stephen P. Messier, Ph.D., at the World Congress on Osteoarthritis.
Exercise also plays a role, he stressed. In fact, "the pain data suggest the combination of diet and exercise is the best," because weight loss offsets the slight increase in joint loads and inflammation that is seen with exercise only. The combination packs a one-two punch: Weight loss impacts the mechanisms of OA, while the combination of diet and exercise impacts the clinical aspects of OA.
Dr. Stephen P. Messier
Dr. Messier, director of the J.B. Snow Biomechanics Laboratory at Wake Forest University, Winston-Salem, N.C., and his colleagues have been looking at the effects of different types of exercise for 20 years. The culmination of this work has resulted in exercise becoming the standard of care in knee OA. "We no longer expect people with knee OA to sit around and do nothing because it hurts. It actually hurts more if they don’t do anything and less if they do," he said
But because many people with OA are obese, Dr. Messier and his colleagues were spurred to investigate the effects of a combination of exercise and weight loss.
They initially carried out investigations with the aim of a 5% weight-loss target, and found clinically significant differences in the patients who followed the diet and exercise program.
But Dr. Messier also found that the 5% weight loss was insufficient to make an impact on the mechanical and physiological pathways. "So we decided to double the weight-loss target to 10%, and we’ve found it has made a difference."
Dr. Messier pointed out that he chose an 18-month over a 6-month program because he wanted this to be a change in lifestyle and something the participants do for the rest of their lives.
Dr. Messier presented primary results from the Intensive Diet and Exercise for Arthritis (IDEA) trial, which involved 454 overweight and obese (body mass index, 27-40.5 kg/m2) adults over age 55 with tibiofemoral OA (Kellgren-Lawrence grade of 2-3). Participants were randomly assigned to three groups: intensive dietary restriction (minimum 1,200 calories for men and 1,100 calories for women), intensive dietary restriction and exercise, or exercise only. More than 85% of participants in each group adhered to their regimen for the full 18-month period.
Exercise involved low- to moderate-intensity walking and resistance training for 3 days per week at 1 hour per day. High-speed motion analysis and musculoskeletal modeling were used to assess biomechanics during exercise and to calculate knee joint loads. Fasting serum concentrations of inflammatory biomarkers also were measured. Results from the three groups were compared at baseline, and at 6 and 18 months combined.
The investigators also conducted a gait analysis with six cameras and a force platform. Participants walked across the platform, and "from this we can determine the loads on the joints," Dr. Messier explained.
Mean weight loss over the 18 months was highest in the diet and exercise group at 11%. For participants on diet alone the loss was 10%, and for exercise alone, 2%.
At the American College of Rheumatology (ACR) meeting in November 2011, the researchers had reported that all three groups reduced pain over the 18 months, with the diet and exercise group reducing pain by approximately 50%. At the study’s end, 4 of 10 (38%) participants in the diet and exercise group reported little or no pain, with pain scores of 0 or 1 on a scale of 0-20, compared with about 2 of 10 for the diet-only and exercise-only groups.
"If you can tell someone you can cut their pain in half without taking drugs, that’s good," he noted.
Walking speed changed in those on the diet and exercise program, showing an increase from 1.20 m/second to 1.34 m/second. Those on diet alone changed from 1.18 meters/second to 1.30 m/second.
Measures of interleukin-6 (IL-6), the primary outcome, decreased significantly in the diet-alone group, with a mean change of –0.43 pg/mL; in the diet and exercise group, the mean change was –0.36 pg/mL; and in the exercise-alone group, it was +0.04 pg/mL (P = .005). Leptin levels also were affected, with changes of –13, –14, and –3 ng/mL in the groups, respectively.
The primary mechanical outcome, knee compressive force, decreased by 174 newtons/step (39.1 pounds/step) in the diet-only group, and by 51 newtons/step (11.5 pounds/step) in the exercise and diet group. Knee compressive force increased by 154 newtons/step (34.6 pounds/step) in the exercise-only group.