Association of a mobile health HH model intervention with BMI changes in office employees: a sex‑stratified prospective non‑randomized controlled cohort study

This study examined the associations of a novel mobile health model integrating the Health Action Process Approach (HAPA) with comprehensive health management strategies, termed the HH model, with body mass index (BMI) and metabolic outcomes among office employees, with a focus on sex differences. This prospective non-randomized controlled cohort study enrolled 4,490 office employees aged 18–60 years. Participants were allocated to the HH model intervention group or a control group receiving standard care. The HH model comprised three phases aligned with HAPA components: intention formation, action planning, and action/maintenance, delivered via a mobile app with personalized feedback, educational modules, and health manager support. Propensity score matching balanced baseline covariates, yielding 4,024 participants (2,012 per group) for final complete-case analysis. Outcomes including BMI, blood pressure, lipids, and fasting plasma glucose were assessed at baseline and 12 months. ANCOVA was used to compare changes between groups. After 12 months, the HH model group showed significantly greater improvements in BMI (adjusted mean difference: -0.151 kg/m²), systolic blood pressure (SBP, adjusted mean difference:-0.96 mmHg), diastolic blood pressure (DBP, adjusted mean difference:-0.826 mmHg) and high-density lipoprotein cholesterol (HDL-C, adjusted mean difference:0.027 mmol/L) compared with controls (all p < 0.05). Total cholesterol (TC) was higher in the HH group than in the control group in the overall population ( p < 0.001) and among men ( p < 0.001). However, the effect sizes were small (Partial η² = 0.005 overall and 0.001 in men), suggesting limited clinical significance. No significant between-group differences were observed for low-density lipoprotein-cholesterol (LDL‑C) and fasting plasma glucose (FPG). After FDR correction, sex-stratified analyses revealed distinct patterns, female participants showed significantly greater improvements in BMI, TG, SBP, and DBP (all p < 0.05). In this non-randomized cohort, the mobile health HH model was associated with modest improvements in BMI, HDL-C and blood pressure among office employees, with sex-specific associations suggesting broader metabolic improvements in females. However, the modest effect sizes and non-randomized design preclude causal claims, and the findings should be interpreted as associations requiring confirmation in future randomized trials. Mechanistic explanations involving HAPA constructs, health-seeking behaviors, or biological sex differences should be considered hypothesis-generating, as these factors were not directly measured. This integrated approach offers a promising workplace strategy for promoting healthier lifestyles and reducing cardiometabolic risk that warrants further evaluation.