Weight loss, not diet type, drives symptom relief in PsA

In the randomised DIPSA trial, 2 personalised dietary interventions and standard dietary advice all produced modest weight loss and improvements in psoriatic arthritis (PsA) disease activity, with no significant differences between approaches. The degree of weight loss, rather than the specific diet intervention, was most strongly associated with symptom improvement.

Diet has an ill-defined place as an adjunctive strategy in PsA, largely because randomised controlled trials in this population are scarce. As Prof. Lihi Eder (University of Toronto, ON, Canada) explained, DIPSA (NCT04180904), a multicentre randomised controlled trial, evaluated whether 2 personalised dietary interventions could improve clinical outcomes compared with standard of care in patients with active disease [1]. Overweight and obese adults (BMI 25-40 kg/m²) with moderately active PsA (Disease Activity Index for PsA (DAPSA) >10) receiving stable drug therapy were recruited from 3 centres between 2021 and 2024. Participants were randomised to 1 of 2 groups: a Mediterranean diet enriched with olive oil and nuts; a low-calorie diet, Dietary Approaches to Stop Hypertension diet (DASH-LC), aimed at weight reduction; or a standard-of-care control group that received general, non-personalised printed dietary advice. Registered dietitians delivered the interventions through 2 in-person consultations and 7 structured telephone sessions, with clinical assessments at baseline and weeks 12 and 24. The primary endpoint was the change in DAPSA at weeks 12 and 24.

Of 92 randomised patients (Mediterranean diet: n=31, DASH-LC: n=30, control: n=31), 12 withdrew after randomisation but remained in the intention-to-treat analysis. Baseline characteristics were comparable, with a mean age of 55±13 years, 70% female participants, a mean BMI of 33±4.3 kg/m², and a mean DAPSA score of 20±11. Overall, 72% of participants were receiving a biologic or targeted synthetic disease-modifying antirheumatic drug (tsDMARD), and 29% were receiving a conventional synthetic DMARD.

All 3 groups experienced modest but statistically significant weight loss by week 12 (Mediterranean diet: -1.36 kg; DASH-LC: -2.47 kg; control: -1.88 kg), with small additional reductions by week 24 and no significant differences between treatment groups. Significant reductions in DAPSA at week 12 were observed in the DASH-LC (-4.93) and control (-4.25) groups, while by week 24 all 3 groups had improved (Mediterranean diet: -4.87; DASH-LC: -5.42; control: -6.53), again without significant between-group differences. Minimal disease activity (MDA) at week 12 was achieved by 38% of patients in the DASH-LC group and 29% in the Mediterranean diet group compared with 16% in the control group (P=0.23 and P=0.06, respectively), although MDA rates were similar across groups by week 24.

Improvements in pain, fatigue, Psoriatic Arthritis Impact of Disease (PsAID) score, and tender joint count were observed across all treatment groups. The magnitude of weight loss was significantly associated with improvements in these outcomes and in DAPSA, independent of treatment group.

These findings suggest that, in overweight or obese patients with PsA, weight loss itself, regardless of the dietary approach used, may represent an effective adjunctive strategy for reducing residual disease activity.

Eder L, et al. Dietary interventions in psoriatic arthritis (DIPSA): a randomised controlled clinical trial. OP070, EULAR 2026, 3–6 June, London, United Kingdom.