This study will adopt a 2-arm, pretest-posttest, and assessor-blind RCT design to examine the effectiveness of a theory-based health behaviour change intervention on WC (primary outcome), kidney function (eGFR, primary outcome), dietary behaviour, PA, exercise capacity, and self-efficacy of dietary behaviour and PA among Chinese adults with metabolic syndrome and chronic kidney disease.

A total of 160 adults with metabolic syndrome and chronic kidney disease will be recruited, with 80 participants in each group. Data will be collected at 3-time points (baseline, immediate post-intervention and 1-month post-intervention) via an online questionnaire survey platform (Qualtrics) by researchers blinded to the group allocation to reduce the detection bias.

Metabolic syndrome (MetS) is a worldwide chronic disease mainly due to unhealthy diets and sedentary lifestyles. According to the International Diabetes Federation (IDF) definition of MetS, patients must have central obesity defined by waist circumference (WC) with ethnicity-specific values, plus any two of four additional factors, namely high triglycerides (TG), low high-density lipoprotein cholesterol (HDL-C), high fasting glucose (FG), and high blood pressure (BP).

More recent evidence indicates that the MetS could be an independent risk factor for chronic kidney disease (CKD). CKD is a progressive and incurable condition with high morbidity and mortality, defined by markers of kidney damage or decreased glomerular filtration rate (GFR) persisting for at least three months. According to KDIGO 2012 clinical practice guideline, CKD is divided into five stages (stages 1, 2, 3a, 3b, 4, 5), which are based on the eGFR test result, as the stage progresses, kidney function becomes more severe, ultimately leading to kidney failure. Previous studies have found that individuals with MetS had a higher risk of CKD compared with patients without MetS.

Central obesity, as the core component of MetS, could be one of the most essential pathogenes explaining the association between MetS and CKD. Central obesity mainly manifests as excess abdominal adipose tissue, which directly leads to the deranged synthesis of various adipose tissue cytokines (e.g., leptin, adiponectin, resistin, and visfatin) with nephrotoxic potential to cause sustained damage or structural changes to the kidneys, as well as indirectly trigger insulin resistance, dyslipidemia and hypertension, which are the most substantial risk factors for CKD.

Many patients fail to take MetS seriously until they are diagnosed with CKD. This is attributed to the additional complications and complex treatments associated with CKD, significantly affecting their daily lives. Current therapeutic guidelines for MetS suggest that non-pharmacological interventions (NPIs) with multifactorial lifestyle changes should be the primary treatment, including dietary modification, physical activity (PA), counselling or lifestyle modifications. Therefore, NPIs could be an essential method for reducing WC and preserving kidney function for the target population. Hence, this proposed study aims to develop an NPI for adults with MetS and CKD on the synthesized scientific evidence, and the effects on health-related outcomes will be evaluated using a randomized controlled trial (RCT) study.

Inclusion Criteria:

• Participants are 18 years old and above;
• Participants have both diagnoses of MetS based on IDF clinical diagnostic criteria (WC for Chinese: ≥ 90 cm in men and ≥ 80 cm in women, and fulfils two items of the following: TG ≥ 1.7 mmol/L or treatment for hypertriglycerides, HDL-C<1.03 mmol/L in men or <1.29 mmol/L in women or treatment for low HDL-C, FG ≥5.6 mmol/L or previously diagnosed type 2 diabetes, and BP ≥ 130/85 mmHg or treatment for hypertension), and CKD;
• Participants are capable of understanding and providing informed consent, their cognitive function will be screened by the abbreviated mental test with a score higher than seven;
• Own a smartphone for accessing WeChat;
• Being able to communicate in Chinese.

Exclusion Criteria:

• Participants who have medical contraindications to exercise, including walking;
• Participants who have already started dialysis or kidney transplant;
• Current participation in another clinical trial related to health behaviour change or medical trial;
• Participants who have doctor-diagnosed psychiatric illness;
• Adjustment of medication within half a year;
• Participants who have performed regular planned exercise (Defined as at least 150 minutes of moderate-intensity aerobic activity or 75 minutes of high-intensity aerobic activity per week, or a combination of moderate-intensity and high-intensity aerobic activity) within the past month.