BMI-Stratified Physiological Responses to a 12-Week Mat Pilates Intervention on Body Composition, Cardiometabolic Risk Factors, and Autonomic Function in Middle-Aged Women: An Exploratory Secondary Analysis

Background/Objectives: Mat Pilates is widely recommended for middle-aged women, but whether baseline obesity modifies its effects remains unclear. This study compared responses to a 12-week mat Pilates programme between non-obese and obese middle-aged women across body-composition, cardiovascular, blood-metabolic, haemorheological and autonomic endpoints. Methods: In an exploratory secondary analysis of a completed, uncontrolled single-arm intervention cohort, de-identified pre- and post-intervention data from 32 premenopausal women (47.5 ± 7.6 years) were stratified by BMI into non-obese (NOG; <25 kg/m2; n = 14) and obese (OG; ≥25 kg/m2; n = 18) groups using WHO Asia-Pacific criteria. All completed identical 60 min sessions three times weekly for 12 weeks, with intensity progressed every four weeks. Outcomes were analysed with mixed-design ANOVA and Bonferroni-corrected paired t-tests. Results: Group × time interactions were significant for body weight, fat mass and percent body fat (p < 0.05). Flow-mediated dilation rose in both groups (NOG +15.6%, OG +29.7%; p < 0.05). Group × time interactions were non-significant for blood pressure, lipids and haemorheology; obesity-dependent claims are therefore restricted to the outcomes with significant interactions (body weight, fat mass, percent body fat). For the remaining outcomes, within-group changes reached significance only in the OG (total cholesterol, LDL-cholesterol, aggregation index, critical shear stress) or only in the NOG (diastolic and mean arterial pressure) but did not differ significantly between groups. Conclusions: Following the programme, endothelial function improved in both groups, whereas body-composition responses differed significantly by obesity status. Because this uncontrolled secondary analysis lacked a non-exercising control group, these associations cannot be attributed causally to mat Pilates. The apparent BMI dependence was not reproduced when adiposity was modelled continuously (baseline BMI, percent body fat or fat mass), so all between-group contrasts are hypothesis-generating. Adequately powered randomised controlled trials with a non-exercising comparator and objective monitoring of diet, non-exercise activity, sleep and menstrual-cycle phase are needed before BMI-dependent adaptations to mat Pilates can be considered established.