Older adults with knee osteoarthritis (OA) who lost 20% or more of their body weight had significant improvements in pain and function, and experienced benefits on multiple other clinical and mechanistic outcomes, a secondary analysis of a randomized study found.

Individuals who lost less than 5% of their body weight over an 18-month period had mean pain scores on the 20-point Western Ontario and McMasters Universities OA index (WOMAC) of 4.46 (95% CI 3.81 to 5.11), whereas those who lost 20% or more had pain scores of 2.79 (95% CI 1.87 to 3.71, P=0.006), according to Stephen P. Messier, PhD, of Wake Forest University in Winston-Salem, N.C., and colleagues.

In addition, at 18 months those who lost less than 5% body weight had scores of 17.13 (95% CI 15.15 to 19.11) on the 68-point WOMAC function index compared with 10.84 (95% CI 8.07 to 13.61, P=0.0005) for those who lost 20% or more, the researchers reported online in Arthritis Care & Research.

The National Institutes of Health currently recommends an initial 10% weight loss for obese and overweight adults.

“The importance of our study is that a weight loss of 20% or greater — double the previous standard — results in better clinical outcomes and is achievable without surgical or pharmacologic intervention,” Messier said in a press release.

Most previous studies of weight loss in OA have reported 5%-10% reductions in body weight, but whether further weight loss would provide additional benefits has not been established.

The Intensive Diet and Exercise for Arthritis clinical trial took place at Wake Forest University from 2006 to 2011, randomizing 240 participants to programs involving diet, exercise, or diet plus exercise.

The initial diet plan provided 1,100 calories per day for women and 1,200 for men, and involved partial meal replacements and a low-fat diet. The exercise program involved an hourlong aerobic plus strength training class three times per week.

Participants’ mean age was 66, most were white women, and mean body mass index (BMI) was 33 kg/m². Clinic visits occurred at baseline, 6 months, and 18 months.

At study completion, participants were stratified as having lost less than 5% of their body weight, having lost 5%-10%, 10%-20%, or more than 20%.

Mean weight changes at 18 months were 0.2% (n=74), 7.4% (n=59), 14.5% (n=76), and 24.6% (n=31), respectively, in the four groups. Corresponding changes in BMI were +0.1, -2.4, -4.7, and -8.1 kg/m².

Mobility was measured on the 6-minute walk test. For patients in the below 5% group, the mean distance at 18 months was 508 meters (95% CI 496 to 520) compared with 559 (95% CI 543 to 576) in the over 20% group (P<0.0001).

Health-related quality of life evaluated on the Short Form-36 questionnaire physical component was 42.5 (95% CI 40.8 to 44.2) in the group with the lowest weight loss compared with 48.1 (95% CI 45.8 to 50.4) among those with the greatest weight loss (P=0.001). On the mental component of the questionnaire, the corresponding numbers were 55.4 (95% CI 53.7 to 57) and 58.1 (95% CI 55.8 to 60.4, P=0.02).

Inflammation was assessed according to plasma interleukin (IL)-6 levels, and also differed significantly according to degree of weight loss. In the lowest weight loss group, the level was 2.84 pg/mL (95% CI 2.41 to 3.26) compared with 2.27 pg/mL (95% CI 1.70 to 2.83, P=0.017).

Knee joint loading, estimated according to the bone-on-bone peak tibiofemoral compressive force, was 2,750 Newtons (95% CI 2,619 to 2,880) in the lowest weight loss group compared with 2.200 (95% CI 2,019 to 2,381, P<0.0001) in the highest group.

The study findings support the notion that “more is better” for weight loss in OA, the authors noted. “The strong trend for pain and function across weight loss groups combined with a clinically important 25% mean reduction in pain and improvement in function when moving from 10% to 20% weight loss argues that there may be additional clinical value with the greater weight loss,” they stated.

One concern has been that major weight loss in older adults might result in bone loss and fracture. While there were dose-response changes in bone mineral density in the study, none of the weight loss groups reached the threshold level for osteopenia.

“We suggest that the significant reduction in pain, inflammation, and knee joint loads combined with significant improvements in function, mobility, and health-related quality of life outweighs the slight reduction in bone mineral density that accompanies a weight loss of 10% or 20% of baseline body weight,” they wrote.

Limitations of the study included its observational design and small number of patients who had a 20% or more weight loss.

Reviewed by Henry A. Solomon, MD, FACP, FACCClinical Associate Professor, Weill Cornell Medical College and Dorothy Caputo, MA, BSN, RN, Nurse Planner

LAST UPDATED 06.20.2018

Primary Source

Arthritis Care & Research

Source Reference: Messier S, et al “Intentional weight loss for overweight and obese knee osteoarthritis patients: Is more better?” Arthritis Care Res 2018; doi:10.1002/acr.23608.