Background: Exercise, weight loss, and dietary supplementation of glucosamine and chondroitin (GC) have been reported to improve functional capacity in individuals with knee osteoarthritis (OA). The purpose of this study was 1.) to determine whether women with knee OA who follow a higher protein diet observe more favorable changes in body composition and/or markers of health compared to those following a standard higher carbohydrate-based diet; and, 2.) to determine whether dietary supplementation of glucosamine and chondroitin during a weight loss and fitness program lessens symptoms of pain, improves functional capacity, and/or promotes greater health benefits in women with knee OA. It was hypothesized that both groups would experience beneficial changes in body mass, body composition, and markers of health. However, greater benefits would be observed in those following a higher protein diet while supplementing the diet with glucosamine and chondroitin.

The study was conducted as a randomized, double-blind, placebo-controlled clinical trial in a university research setting. Participants with physician diagnosed OA participated in a 14-week fitness and weight loss program that consisted of moderately hypo-energetic higher protein or higher carbohydrate diets. Participants were also randomly assigned to ingest in a double-blind and randomized manner either a placebo or a commercially available dietary supplement containing glucosamine and chondroitin. Outcome measures were assessed at 0, 10, and 14 weeks of training, dieting, and supplementation.

Inclusion Criteria:

- General entrance criteria included being a female with physician diagnosed OA between the ages of 18-70 years with a body mass index (BMI) > 27 kg/m2 and no recent participation in a diet or exercise program.

Exclusion Criteria:

- Subjects were not allowed to participate in this study if they: 1.) were pregnant, became pregnant, or had a desire for pregnancy; 2.) had any metabolic disorder including known electrolyte abnormalities, heart disease, arrhythmias, diabetes, thyroid disease, or hypogonadism; 3.) had a history of hypertension, hepatorenal, musculoskeletal, autoimmune, or neurological disease; were taking thyroid, hyperlipidemic, hypoglycemic, anti-hypertensive, or androgenic medications; 4.) had taken ergogenic levels of nutritional supplements that may affect muscle mass (e.g., creatine, HMB), anabolic/catabolic hormone levels (e.g., DHEA), or weight loss supplements (e.g., thermogenics) within three months prior to the start of the study; 5.) were ingesting any anti-inflammatory products two weeks before the start of the study or additional products during the study; 6.) reported any unusual adverse events associated with this study in which the supervising physician recommended removal from the study; 7.) had significant injury or surgery to the lower extremity or spine within the last six months; 8.) did not indicate a minimal amount of perceived pain and physical function limitation on inventories used in the study; 9.) had severe arthritis that required surgery and greatly limited functionality (inability to perform lunge); or, 10.) had arthritis that required the current use of physiotherapy modalities.