Effects of intensive diet and exercise on knee joint loads, inflammation, and clinical outcomes among overweight and obese adults with knee osteoarthritis: the IDEA randomized clinical trial

Abstract

Importance: Knee osteoarthritis (OA), a common cause of chronic pain and disability, has biomechanical and inflammatory origins and is exacerbated by obesity.

Objective: To determine whether a ≥10% reduction in body weight induced by diet, with or without exercise, would improve mechanistic and clinical outcomes more than exercise alone.

Design, setting, and participants: Single-blind, 18-month, randomized clinical trial at Wake Forest University between July 2006 and April 2011. The diet and exercise interventions were center-based with options for the exercise groups to transition to a home-based program. Participants were 454 overweight and obese older community-dwelling adults (age ≥55 years with body mass index of 27-41) with pain and radiographic knee OA.

Interventions: Intensive diet-induced weight loss plus exercise, intensive diet-induced weight loss, or exercise.

Main outcomes and measures: Mechanistic primary outcomes: knee joint compressive force and plasma IL-6 levels; secondary clinical outcomes: self-reported pain (range, 0-20), function (range, 0-68), mobility, and health-related quality of life (range, 0-100).

Results: Three hundred ninety-nine participants (88%) completed the study. Mean weight loss for diet + exercise participants was 10.6 kg (11.4%); for the diet group, 8.9 kg (9.5%); and for the exercise group, 1.8 kg (2.0%). After 18 months, knee compressive forces were lower in diet participants (mean, 2487 N; 95% CI, 2393 to 2581) compared with exercise participants (2687 N; 95% CI, 2590 to 2784, pairwise difference [Δ](exercise vs diet )= 200 N; 95% CI, 55 to 345; P = .007). Concentrations of IL-6 were lower in diet + exercise (2.7 pg/mL; 95% CI, 2.5 to 3.0) and diet participants (2.7 pg/mL; 95% CI, 2.4 to 3.0) compared with exercise participants (3.1 pg/mL; 95% CI, 2.9 to 3.4; Δ(exercise vs diet + exercise) = 0.39 pg/mL; 95% CI, -0.03 to 0.81; P = .007; Δ(exercise vs diet )= 0.43 pg/mL; 95% CI, 0.01 to 0.85, P = .006). The diet + exercise group had less pain (3.6; 95% CI, 3.2 to 4.1) and better function (14.1; 95% CI, 12.6 to 15.6) than both the diet group (4.8; 95% CI, 4.3 to 5.2) and exercise group (4.7; 95% CI, 4.2 to 5.1, Δ(exercise vs diet + exercise) = 1.02; 95% CI, 0.33 to 1.71; P(pain) = .004; 18.4; 95% CI, 16.9 to 19.9; Δ(exercise vs diet + exercise), 4.29; 95% CI, 2.07 to 6.50; P(function )< .001). The diet + exercise group (44.7; 95% CI, 43.4 to 46.0) also had better physical health-related quality of life scores than the exercise group (41.9; 95% CI, 40.5 to 43.2; Δ(exercise vs diet + exercise) = -2.81; 95% CI, -4.76 to -0.86; P = .005).

Conclusions and relevance: Among overweight and obese adults with knee OA, after 18 months, participants in the diet + exercise and diet groups had more weight loss and greater reductions in IL-6 levels than those in the exercise group; those in the diet group had greater reductions in knee compressive force than those in the exercise group.

Trial registration: clinicaltrials.gov Identifier: NCT00381290.

Figure 1. Participant Progress Through the Intensive Diet and Exercise for Arthritis (IDEA) Trial

Body mass index (BMI) was calculated as weight in kilograms divided by height in meters squared. ADLs indicates activities of daily living; CES-D, Center for Epidemiologic Studies Depression scale; WOMAC, Western Ontario and McMaster Universities Osteoarthritis Index. ^aParticipant may be ineligible for >1 reason.

Figure 2. Mean WOMAC Pain Scores Across the 18-Month Intervention Period

The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain subscale was used to measure self-reported pain while performing daily living activities in the last 48 hours due to knee osteoarthritis. Total scores range from 0 to 20; higher scores indicate greater pain. The estimates are based on the previously stated number of observations and multiply imputed values for the missing observations within each group adjusted for baseline body mass index, sex, and baseline values. P = .002 comparing the diet + exercise group with the diet group and exercise group. Error bars indicate 95% CIs.