Effects of a Mediterranean Diet Compared with the Low-Fat Diet on Patients with Knee Osteoarthritis: A Randomized Feeding Trial

Objectives. Knee osteoarthritis is a common global problem, especially in overweight and obese people. It is not clear that weight loss is a factor for pain reduction in these patients or dietary components are important. Herein, we compared the effects of Mediterranean (MD) and low-fat diet on pain, stiffness, and physical function in patients with knee osteoarthritis. Subjects/Methods. In this randomized feeding trial, 129 patients with knee osteoarthritis were enrolled. Participants were randomly allocated to the MD (n = 43), low-fat diet (n = 43), and control group (regular diet) (n = 43) for 12 weeks by the blocked randomization method. Total Western Ontario and McMaster Universities Arthritis Index (WOMAC) score and its subscales and anthropometric indices were compared among the groups at the baseline and end of the study. Results. Weight and waist circumference reduction was significantly higher in the MD and low-fat diet groups compared with the regular group (p < 0.001 and p < 0.001, respectively), but there was no significant difference between the MD and low-fat diet groups (p = 0.2). Pain was significantly decreased in the Mediterranean-style compared with the low-fat (p = 0.04) and regular (p = 0.002) diet groups. Physical function was significantly improved in the MD compared with the regular diet group (p = 0.01), but had no significant difference with the low-fat one. Stiffness had no significant difference among the dietary groups. Conclusions. Pain severity was reduced in the MD group, but no significant change was reported in patients on low-fat and regular diets. It seems that dietary components in the MD, regardless of weight loss effect, are effective on pain reduction in patients with KOA. The present study was registered in the IRCT under the code of IRCT20200929048876N1.