Meal size has been researched extensively in relation to a number of metabolic effects, specifically fat loss and weight gain. In this regard it is generally accepted that smaller meals may offer some protection from excessive weight gain and may aid fat loss efforts. The reason for this is likely that smaller meals do not overload the hepatic system and therefore the pathways through which the nutrients pass are more efficient. Large meals likely overload the ability of the liver to efficiently process the nutrients and as a result the de novo lipogenesis pathway converts more of the carbohydrate content to fatty acids, which subsequently increase fat deposition. As well as causing hepatic burdon, large meals may burden the cardiovascular system. The requirement for the circulation of nutrients is important postprandially, and blood flow to the intestine must increase to allow efficient absorption. Therefore as meal size increases, cardiac burden also increases to allow for the efficient absorption and transport of nutrients.
Some researchers have measured the demands on the circulatory system following ingestion of meals of different size. For example, one study fed healthy volunteers meals ranging from 15 to 75 % of total daily energy requirements as a single meal and measured cardiac function1. The results showed that there was a positive association between meal size and cardiac index, stroke volume, heart rate, myocardial oxygen consumption and whole body oxygen consumption. However, there was no significant changes to blood pressure. As well as increasing cardiac function peak values, meals over 35 % of the total daily energy needs significantly increased the duration of the elevated cardiac response compared to meals less than 35 % of the total daily energy requirement. These results illustrate that energy demand increase considerably following a meal and that smaller meals place a lower stress on the cardiovascular system. This could have implications for those with cardiovascular disease or other heart complications.