BACKGROUND: Long-term high-fat diet (HFD) consumption causes obese-insulin resistance which is known to be a major risk factor for cardiovascular diseases due to its impact on the impairment of left ventricular (LV) contractile function and cardiac mitochondrial function. Intracellular calcium [Ca(2+)]i regulation plays an important role in the maintenance of LV function. Although either caloric restriction (CR) or exercise (Ex) are shown to strongly affect metabolic status and LV function, the combined effects of exercise and calorie restriction on cardiometabolic status, cardiac mitochondrial dynamics and cardiac [Ca(2+)]i transient homeostasis under conditions of obese-insulin resistance have never been investigated. METHODS: Female rats were fed with either a high-fat diet (HFD: fat, 59.28%; protein, 26.45%; carbohydrate, 14.27%) or a normal diet (fat, 19.77%; protein, 28.24%; carbohydrate, 51.99%) for 13鈥痺eeks. HFD rats were then divided into 4 groups: 1) Vehicle (HFD鈥?鈥疺eh); 2) Calorie restriction (HFD鈥?鈥疌R); 3) Exercise (HFD鈥?鈥疎x) and 4) Combined therapy (HFD鈥?鈥疌R鈥?鈥疎x). After 6-week intervention, the metabolic status, heart rate variability (HRV), LV function, cardiac mitochondrial dynamics, and [Ca(2+)]i transients were determined. RESULTS: Insulin resistance developed in HFD rats as indicated by increased plasma insulin and HOMA index. Although HFD鈥?鈥疺eh rats had markedly impaired LV function, indicated by reduced %LVFS and impaired cardiac mitochondrial dynamics and [Ca(2+)]i transients, these impairments were attenuated in the HFD鈥?鈥疌R, HFD鈥?鈥疎x and HFD鈥?鈥疌R鈥?鈥疎x rats. However, the greatest improvement in cardiometabolic function was observed in HFD +鈥疌R鈥?鈥疎x rats. CONCLUSIONS: Our findings indicated that a combination of calorie restriction and exercise exerted greater cardioprotection than a monotherapy through the improvement of cardiometabolic status, cardiac mitochondrial dynamics and cardiac [Ca(2+)]i homeostasis in obese-insulin resistant rats.