Effect of a multidisciplinary lifestyle intervention on body composition in people with osteoarthritis: Secondary analysis of the "Plants for Joints" randomized controlled trial.

Objective: The Plants for Joints (PFJ) intervention significantly improved pain, stiffness, and physical function, and metabolic outcomes, in people with metabolic syndrome-associated osteoarthritis (MSOA). This secondary analysis investigated its effects on body composition.

Method: In the randomized PFJ study, people with MSOA followed a 16-week intervention based on a whole-food plant-based diet, physical activity, and stress management, or usual care. For this secondary analysis, fat mass, muscle mass, and bone mineral density were measured using dual-energy X-ray absorptiometry (DEXA) for all participants. Additionally, in a subgroup ( ​= ​32), hepatocellular lipid (HCL) content and composition of visceral adipose tissue (VAT) were measured using magnetic resonance spectroscopy (MRS). An intention-to-treat analysis with a linear-mixed model adjusted for baseline values was used to analyse between-group differences.

Results: Of 66 people randomized, 64 (97%) completed the study. The PFJ group experienced significant weight loss (-5.2 ​kg; 95% CI -6.9, -3.6) compared to controls, primarily from fat mass reduction (-3.9 ​kg; 95% CI -5.3 to -2.5). No significant differences were found in lean mass, muscle strength, or bone mineral density between groups. In the subgroup who underwent MRI scans, the PFJ group had a greater reduction in HCL (-6.5%; 95% CI -9.9, 3.0) compared to controls, with no observed differences in VAT composition.

Conclusion: The PFJ multidisciplinary intervention positively impacted clinical and metabolic outcomes, and appears to significantly reduce body fat, including liver fat, while preserving muscle mass and strength.