Hiit vs. Mict for Cardiometabolic Health in Middle-Aged Adults With Metabolic Syndrome: A Randomized Controlled Trial

Background Metabolic syndrome represents a growing public health concern, particularly among middle-aged adults. Exercise interventions such as high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) have been proposed as potential strategies for mitigating cardiometabolic risk. However, comparative evidence across multiple physiological systems in at-risk populations remains limited. Methods In this 12-week randomized controlled trial, 90 adults aged 40–65 years with metabolic syndrome were stratified by sex and randomly assigned to HIIT, MICT, or a non-exercising control group (n = 26 per group). Seventy-eight participants completed the intervention. The HIIT group followed a 4×4-minute interval protocol, while the MICT group performed continuous aerobic exercise. Primary outcomes included fasting blood glucose (FBG), glycated hemoglobin (HbA1c), triglycerides (TG), HDL cholesterol (HDL-C), alanine aminotransferase (ALT), uric acid (UA), high-sensitivity C-reactive protein (hs-CRP), and heart rate recovery (HRR). Measurements were conducted at baseline, midpoint, and post-intervention. Data were analyzed using mixed-model ANOVA and structural equation modeling. Results Compared to the MICT and control groups, participants in the HIIT group exhibited greater reductions in FBG (− 0.68 mmol/L), HbA1c (− 0.72%), TG (> 1.0 mmol/L), ALT, UA, and hs-CRP ( ~ − 1.0 mg/L), alongside increases in HDL-C (> 0.3 mmol/L) and HRR (+ 8 bpm) (all p < 0.05). These patterns were generally observed across both sexes, although some sex-specific variations were noted. The MICT group showed modest but statistically significant improvements in several outcomes. Conclusions This study suggests that HIIT may offer time-efficient benefits across multiple cardiometabolic domains in middle-aged adults with metabolic syndrome. While both exercise modalities were associated with favorable changes, HIIT was linked to more pronounced improvements in glycemic, lipid, hepatic, and autonomic parameters. These findings support further exploration of structured HIIT protocols as part of individualized lifestyle interventions in clinical and public health contexts. Trial registration: ISRCTN18045412. The study was retrospectively registered on 23/07/2025 at https://www.isrctn.com/ISRCTN18045412.