The Effectiveness of a Theory-Based Health Behaviour Change Intervention on Waist Circumference and Kidney Function in Patients with Metabolic Syndrome and Chronic Kidney Disease: A Pilot Randomised Controlled Trial

Metabolic syndrome (MetS) is an independent risk factor for chronic kidney disease (CKD), with central obesity measured by waist circumference (WC) as a core pathogenic driver. Despite evidence supporting non-pharmacological interventions for MetS, their effectiveness in reducing WC and preserving kidney function among patients with MetS and CKD remains underexplored. This pilot randomized controlled trial (RCT) evaluated the feasibility, acceptability and preliminary effectiveness of a theory-based health behaviour change intervention on WC and kidney function in Chinese adults with MetS and CKD.

This study employed a two-arm, parallel-group, assessor-blinded pilot RCT conducted in China from July to October 2024. Adults with MetS and CKD were randomised 1:1 to the intervention group or the control group. The intervention group received an eight-session health behaviour change intervention guided by the Health Action Process Approach (HAPA), which aimed to promote dietary modifications and at least 150 minutes per week of music-paced brisk walking over three months. The control group received usual care. The primary outcomes, including WC, estimated glomerular filtration rate (eGFR) and urine albumin-to-creatinine ratio (UACR), as well as secondary outcomes (MetS-related components and health-related behaviours), were assessed at baseline and immediate post-intervention. Group differences were analysed using independent samples t-tests, with effect sizes (ES) calculated using Cohen's d to quantify the magnitude of the observed differences. The two-sided level of significance was set at 0.05. The feasibility (recruitment, retention, attendance and compliance rate) and acceptability (semi-structured interviews) of the intervention were also evaluated.

A total of 40 participants (female: 45%; mean age: 48.6±15.3 years) were enrolled, and no significant differences in baseline characteristics were observed between the groups. At immediate post-intervention, compared to the control group, the intervention group had significantly lower mean values for WC (moderate ES, Cohen's d=0.65), triglycerides (small ES, Cohen's d=0.31), systolic blood pressure (moderate ES, Cohen's d=0.73) and diastolic blood pressure (small ES, Cohen's d=0.10). The intervention group also showed a higher mean score on the Diet Control Subscale of the Chronic Kidney Disease Self-Care (large ES, Cohen's d=0.82), the International Physical Activity Questionnaire (large ES, Cohen's d=0.82), the 6-minute Walk Test (large ES, Cohen's d=1.05), and the Health-Related Diet and Exercise Self-Efficacy Scale (large ES, Cohen's d=1.12) (all p<0.05). No significant between-group differences were found for eGFR and UACR. Besides, the intervention demonstrated high feasibility, as reflected by a perfect retention rate (100%), a near-perfect attendance rate (99.4%) and a strong compliance rate (97.5%). Qualitative findings from semi-structured interviews revealed the high acceptability of the intervention, with participants reporting positive experiences and perceived benefits.

Findings support the feasibility and acceptability of the HAPA-based health behaviour change intervention to improve MetS-related components and health behaviours in MetS with CKD. A fully powered RCT with longer follow-up is warranted to confirm efficacy in preserving kidney function.