PHILADELPHIA – There are few certainties in medicine, but most would agree that exercise is good for you.
In older, largely postmenopausal women, a recent systematic review showed that exercise does indeed prevent weight gain, preserves lean body mass when combined with weight loss, and is a key determinant for the positive effects of weight loss later in life (Maturitas. 2012;72:13-22).
What’s not clear, however, is whether exercise plays the same positive role in weight loss in older, obese patients with knee osteoarthritis, Stephen P. Messier, Ph.D., said at the World Congress on Osteoarthritis.
"Once you take that leap – make that decision to lose weight – the question is: ‘Does exercise enhance, impede, or have no effect on the process and the potential outcomes?,’ " said Dr. Messier, professor and director of the J.B. Snow Biomechanics Laboratory at Wake Forest University, Winston-Salem, N.C.
Patrice Wendling/IMNG Medical Media
Dr. Stephen Messier
The question is highly relevant, as the risk of developing knee OA is up to 12 times higher in obese men and up to 17 times higher in obese women (Arthritis Res. Ther. 2010;12:R88).
Dr. Messier reviewed data from two long-running randomized intervention trials at Wake Forest, suggesting that exercise does not impede weight loss. Compliance was 61% for diet only and 63% for diet plus exercise in ADAPT (Arthritis, Diet and Activity Promotion).
On the other hand, adding exercise to diet doesn’t dramatically enhance weight loss, acknowledged Dr. Messier, principal investigator of ADAPT and of the IDEA (Intensive Diet and Exercise for Arthritis) trial, which had a weight loss goal of at least 10% of body weight, or twice the goal of ADAPT.
Patients who adhered to a diet with or without exercise lost more weight than did those who did neither in ADAPT, but just 2 kilograms of weight loss separated the diet-plus-exercise group from the diet-only group in IDEA. Fat loss was similar.
What was concerning was that the addition of exercise to diet did not prevent the loss of lean mass, Dr. Messier said. The mean change in lean mass was –4.2 with intensive dietary restriction vs. –4.7 with the same diet plus 15 minutes of walking and 20 minutes of weight training thrice-weekly in IDEA.
The silver lining
Knee OA patients and their physicians can take heart, as virtually every clinical outcome favored diet plus exercise over diet alone, Dr. Messier observed.
When exercise was combined with diet for 18 months, patients experienced a 30% decrease in pain and 24% improvement in function in ADAPT, with even higher results of 51% and 47% in IDEA.
"The big take-home message was that the diet and exercise group had a 50% reduction in pain, and you don’t find that with any pharmacologic intervention," he said in an interview.
Dr. Messier speculated that the loss of lean body mass with diet plus exercise could be offset by adding strength training – a tactic that is currently being studied in 370 patients with knee OA in START (Strength Training for Arthritis Trial).
"A more intensive strength training regimen may build muscle and attenuate the loss of lean body mass," he said. "If it works, we could get the best of both worlds."
Diet driving mechanistic changes
Interestingly, the data suggest that diet alone may be slightly better than diet plus exercise in improving mechanistic outcomes, Dr. Messier said.
Among the 142 sedentary overweight/obese older adults with knee OA in ADAPT, every 1 pound of weight loss resulted in a fourfold reduction in compressive forces exerted on the knee per step (Arthritis Rheum. 2005;52:2026-32).
The average change in knee compressive forces from baseline in IDEA was 11% with diet alone, 9% with diet plus exercise, and 5% with exercise alone. Reductions in interleukin-6, a marker of physical disability in older adults, were also significantly better with diet than with diet plus exercise, and the decrease was independent of gender, body mass index and other baseline values.
"Once again, it is the weight loss that counts," he said.
That said, should clinicians push their knee OA patients to exercise and diet?
Diet plus exercise should be the standard of care in our older adults with osteoarthritis of the knee, Dr. Messier concluded.
"OA and other obesity-related diseases place an enormous physical and financial burden on our health care system," he said. "Intensive weight loss, when combined with exercise, can safely achieve a mean long-term weight loss of 11.4% for compliant patients and they can expect significant improvement in symptoms relative to either exercise or diet alone. Wider adoption of intensive weight loss combined with exercise can reduce the burden of disability related to OA and obesity in our aging population."