Study design of a pilot randomized digital health intervention to support lifestyle management in adults with metabolic syndrome

Technical Summary: Study Design of a Pilot Randomized Digital Health Intervention for Metabolic Syndrome

Problem Statement
Noncommunicable diseases (NCDs), particularly cardiovascular diseases (CVD), represent a leading cause of global mortality, with metabolic syndrome (MetS) serving as a critical precursor cluster of risk factors including abdominal obesity, dyslipidemia, hypertension, and impaired glycemia. In Chile, the prevalence of MetS is estimated at 40.1% among adults, rising to 58% in the 45–64 age bracket. While regular consumption of oily fish (rich in n-3 fatty acids, bioactive peptides, and essential nutrients) is supported by evidence as a strategy to reduce cardiometabolic risk, there is a lack of controlled, species-specific interventions tailored to local contexts. Furthermore, while mobile health (mHealth) technologies offer scalable tools for lifestyle modification, there is a notable gap in research integrating evidence-based nutritional strategies with mHealth interventions specifically for Chilean adults with MetS. Current preventive approaches often lack the scalability and personalization required to address the complex determinants of NCDs effectively.

Methodology
This paper outlines the design and rationale of a pilot, investigator-initiated, randomized, controlled, parallel-group intervention trial. The study targets Chilean adults aged 45–64 years diagnosed with metabolic syndrome.

• Study Arms:

  • Intervention Group: Receives an 8-week program comprising the provision of 400 g/week of jack mackerel (distributed as three portions) and personalized nutrition education delivered via an mHealth system. The digital curriculum includes weekly instant messaging: cognitive-behavioral motivation on Mondays and nutrition education (approx. 60% fish-focused) on Tuesdays and Thursdays.
  • Control Group: Receives the same provision of jack mackerel (400 g/week) and outcome assessments but does not receive the mHealth educational component. This design isolates the incremental effect of the digital educational strategy on adherence and engagement.

• Participants and Randomization: The target sample size is 40 participants (20 per arm), randomized 1:1. Randomization is stratified by sex and baseline health status (presence of hypertension, diabetes, or prior cardiovascular conditions). While participants and providers cannot be blinded due to the nature of the intervention, outcome assessors and data analysts remain blinded until primary analysis completion.

• Data Collection and Outcomes:

  • Primary Outcomes (Feasibility): Focus on recruitment rates, retention, data completeness, intervention fidelity (message delivery/receipt), platform engagement analytics, and self-reported adherence to the prescribed fish intake (400 g/week).
  • Secondary Exploratory Outcomes: Changes in anthropometric and cardiometabolic parameters from baseline to week 8, including waist circumference, blood pressure, triglycerides, HDL-C, and fasting glucose.
  • Dietary Assessment: Utilizes 24-hour dietary recalls (five-step method), food frequency questionnaires (focused on animal-source proteins), and the Healthy Eating Index (HEI) at baseline, week 4, and week 8.

• Statistical Analysis: The analysis plan prioritizes estimation (mean changes, adjusted mean differences, standardized effect sizes like Hedges g) with 95% confidence intervals over formal hypothesis testing, consistent with pilot study objectives. Between-group differences will be assessed using Analysis of Covariance (ANCOVA) adjusting for baseline values, with mixed-effects models used to account for within-subject correlation. Missing data will be handled via multiple imputation.

Key Contributions
The primary contribution of this work is the detailed protocol for a pilot trial that integrates a specific, locally relevant nutritional intervention (jack mackerel consumption) with mHealth technology. Key design features include:

1. Local Relevance: The selection of jack mackerel is grounded in its local availability, cost-effectiveness, and substantial n-3 fatty acid profile, addressing the need for culturally adapted interventions in Chile.
2. Methodological Rigor in Feasibility: The study explicitly defines metrics for feasibility, acceptability, and implementation, including specific strategies for monitoring adherence through both digital engagement analytics and repeated dietary recalls.
3. Isolation of Variables: By providing fish to both groups, the design controls for the nutritional effects of fish consumption, allowing the researchers to specifically evaluate the added value of the mHealth educational component on adherence and engagement.
4. Ethical and Safety Framework: The protocol includes comprehensive measures for data confidentiality, adverse event monitoring (specifically for fish-related allergies or gastrointestinal issues), and clear criteria for participant discontinuation.

Results
As this paper describes the study design and rationale of a pilot trial, it does not report empirical results, statistical findings, or clinical outcomes. The text explicitly states that the study is intended to assess feasibility and implementation characteristics to inform a future definitive trial. Consequently, no data regarding changes in metabolic indicators or adherence rates are presented in this document.

Significance and Claims
The authors position this study as a necessary preliminary step to generate methodological and practical insights for implementing digital health interventions in cardiometabolic care. The significance of the work lies in its potential to:

• Inform Future Trials: Provide preliminary evidence on the feasibility, acceptability, and implementation characteristics of an mHealth-supported fish promotion program, which will guide the design, outcome selection, and sample size calculation of a future fully powered randomized trial.
• Bridge the Evidence Gap: Address the lack of integrated studies combining evidence-based nutritional strategies (specifically jack mackerel) with mHealth tools in the Chilean population.
• Refine Intervention Strategies: Use qualitative feedback and engagement metrics to iteratively refine the content and delivery of the digital intervention before scaling.

The paper modestly claims that while the pilot will not evaluate clinical effectiveness for regulatory approval, it aims to determine if such an approach is viable and acceptable, thereby laying the groundwork for scalable, sustainable alternatives to traditional lifestyle counseling in the prevention and management of metabolic syndrome.