Background and aim <p>Sedentary lifestyle and obesity are considered to be significant risk factors that create a pathway for the appearance of the ‘sedentary cardiac phenotype’ consisting of cardiac atrophy, myocardial stiffening, and altered haemodynamics. Although exercise training has the potential to reverse this detrimental process, the literature data on the magnitude of improvements and the certainty of evidence are inconsistent. This systematic review and meta-analysis aimed to evaluate the effects of exercise interventions on cardiac morphology, systolic/diastolic function, and haemodynamics in sedentary and obesity-prone individuals.</p> Method <p>In accordance with the PRISMA guidelines, the study was conducted by searching the PubMed, Web of Science, and Scopus databases from 1990 to 2025 without applying any filters, using Covidence software. As a result of this comprehensive search, 12 randomised controlled trials (RCTs; N=477) comparing exercise training with a control group in sedentary individuals were included in the analysis. Data were pooled using the Standardised Mean Difference (SMD) and a random-effects model. Publication bias and methodological robustness of the results were tested using the Egger regression test, the Trim-and-Fill method, and Leave-One-Out sensitivity analysis. The certainty of the evidence was graded using the GRADE system.</p> Results <p>Exercise training was associated with significant reductions in resting HR and SBP, indicating robust improvements in the haemodynamic profile. Notably, stroke volume (SV) demonstrated a highly significant increase. While global LVEF improvements remained at the statistical threshold, myocardial contractility—measured by the S' wave—improved significantly. Furthermore, exercise induced a physiological, athlete’s heart-like eccentric hypertrophy, evidenced by significant increases in LVMass and LVEDV without pathological wall thickening. Diastolic adaptations were also marked by substantial improvements in the E/A ratio and IVRT. Subgroup analyses indicated that high-intensity interval training (HIIT) was the superior modality for diastolic and structural adaptations, whereas aerobic exercise was the most effective for blood pressure reduction. Importantly, meta-regression analyses revealed two key findings: first, improvements in blood pressure and diastolic function occurred independently of weight loss; second, structural and functional adaptations were linearly associated with improvements in body composition.</p> Conclusion <p>Exercise training may reduce selected cardiovascular adverse effects associated with obesity and a sedentary lifestyle, particularly in terms of haemodynamic and diastolic parameters. Structural cardiac adaptations, however, may be more closely linked to changes in BMI. Findings specific to HIIT and aerobic training modalities are exploratory in nature and should be interpreted with caution due to heterogeneity and the limited number of studies.</p> Trial registration <p>The systematic review protocol was preregistered in PROSPERO (CRD420261292046).</p>