Exploring the role of diet quality and adiposity in the pain experience: a mediation analysis.

Purpose: Improving diet quality may lower chronic musculoskeletal pain (CMP) directly or through weight loss. This study examined whether a dietary intervention for weight-loss improved diet quality and CMP in adults with elevated adiposity. It also investigated whether adiposity mediated a relationship between diet quality and pain. Methods: This secondary analysis of data from another study included 104 Australian adults (25–65 years) with overweight/obesity (BMI, 27.5–34.9 kg/m²) who completed a 3-month dietary intervention targeting 30% energy restriction. Baseline and 3-month measures included diet quality (Dietary Guideline Index (DGI)), presence of CMP, pain related quality-of-life (Short-Form-36 bodily pain scale (SF36-BPS)), pain severity (McGill Pain Questionnaire (MPQ)) and adiposity (weight, waist circumference (WC), percent body fat (BF)). Linear mixed models estimated the effect of the dietary intervention on these outcomes. Structural equation modelling estimated the direct effects of changes in diet quality on CMP, and proportion mediated by changes in adiposity. Results: Participants improved diet quality (DGI total score) by 22% (p < 0.001) and achieved weight loss (− 7.1 ± 0.3 kg, 95% CI − 7.7, − 6.4). Presence of CMP reduced from 50 to 24% (p < 0.001). Pain-related quality of life improved, and pain severity lessened. Reductions in weight, WC, or BF did not mediate improvements in pain characteristics. Improved diet quality (∆DGI) was directly associated with lower pain severity (∆MPQ), accounting for reductions in the mediator, WC (β = − 0.085, 95% CI − 0.151, − 0.019) and BF (β = − 0.073, 95% CI − 0.135, − 0.012). Conclusion: On average, diet quality improved and pain lessened following a 3-month dietary intervention for weight-loss. Changes in adiposity did not mediate this relationship.