A new approach for studying the thermic response to dietary fuels.

We describe a new method of studying the thermic response to dietary fuels that involves continuous infusion of a liquid formula diet through a thin nasogastric tube. The data show that the steady inflow of dietary fuel is accompanied by a relatively constant level of energy expenditure, the magnitude of which depends on the rate of fuel inflow. An increase in the rate of fuel infusion above that required for caloric maintenance leads to a rise in energy expenditure. We also give examples, based on preliminary observations, of how the technique can be used to more precisely quantify energy metabolism. The technique may prove useful in the studying efficiency of energy utilization and in examining the extent to which individuals differ in energy efficiency.