Effect of meal size on myocardial oxygen requirements: implications for postmyocardial infarction diet.

The validity of the assumption that eating a small meal places less postprandial demands on the circulatory system than eating a large meal was examined in eight healthy volunteers. Five meal sizes that ranged from 15 to 75% of daily energy requirements were fed. There was a significant correlation between meal size (in percentage of daily caloric requirements) and peak percentage change in cardiac index (p less than 0.001) and stroke volume (p less than 0.05) (echocardiography); heart rate (p less than 0.001); an index of myocardial oxygen consumption (heart rate X mean blood pressure) (p less than 0.01); and whole body oxygen consumption (p less than 0.001). There was no significant correlation between meal size and peak percentage change in systolic and diastolic blood pressure. The duration of hemodynamic and metabolic changes that followed medium and large meals (greater than or equal to 35% of daily energy needs) exceeded smaller meals (less than or equal to 25% of energy needs). These results may have implications in the management of patients with ischemic heart disease.