36 normotensive obese and 23 hypertensive obese were treated with an isokaloric reduction diet of 800 kcal/a day under clinical conditions over a 4-week span. Blood pressure and cardiac performance were investigated by means of non-invasive techniques such as systolic time intervals (STI) and calculated indices. A significant decrease was established in systolic time intervals such as left ventricular ejection time and total electromechanical systole, systolic and diastolic blood pressure, myocardial oxygen consumption and cardiac output. Heart rate, preejection index and stroke volume were not diminished under dietary treatment. No decrease of all parameters was found in obese normotensives with a weight reduction greater than 5% after dietary treatment.