Energy Expenditure and Substrate Oxidation in a Whole Room Calorimeter

The investigators aim to establish a protocol for metabolic rate measurements obtained using continuous monitoring of oxygen consumption and carbon dioxide production in a whole room calorimeter setting.

The purpose of this study is to determine the duration and time course of the thermic effect of single meals consumed by subjects who have been previously fasting for 12 hours overnight. Capturing the full thermic effect of a meal may take up to 8 hours, depending on the calorie load, nutrient composition of the meal, and rate of digestion. The investigators will test meals consisting of conventional foods that are low (20% of energy), moderate (40% of energy) or high (60% of energy) in fat calories, as fat is thought to slow the digestive process. The investigators will test a liquid meal, that is high (60% of energy) in fat calories, as liquid foods are thought to move more quickly through the digestive process. Another purpose of this study is to determine the test-retest reproducibility for the meals described above. To accomplish reproducibility, a volunteer will be permitted to repeat a test day two times using the same test meal.