Research Goal
Our studies are aimed to improve our understanding of normal human physiology and metabolic dysfunction in diseases such as obesity.

Current Research
My laboratory focuses on human energy metabolism as it relates to health and disease.  We have developed advanced techniques such as the whole-room indirect calorimeters (also called respiration or metabolic chambers) that we use to measure the rate of energy expenditure at the minute-by-minute level and substrate oxidation for several hours or for several days.  We can also simultaneously measure movement and physiological parameters in this well-controlled environment to study the impacts of physical activities, diets, medications, and environmental temperatures on energy metabolism, heart rate, and hormonal responses. Currently, we are working to improve our understanding of human dynamic regulation of energy expenditure in response to subtle changes in environmental temperature. In particular, we are interested in studying the capacity of facultative thermogenesis, defined as an increase in energy expenditure (EE or heat production) to a changed environmental temperature. Combined with the ongoing research on brown adipose tissue (BAT), we are also quantifying the different contributions from BAT and muscle in lean and obese individuals.  We are also developing new technologies for measuring body composition and physical activity in humans.​ 

Potential Summer Project:
To improve the metabolic chamber signal processing, data analysis, and performance. The metabolic chamber measures oxygen consumption and carbon dioxide production and calculates EE and respiratory quotient (RQ, which is a marker of carbohydrate vs. fat oxidation). To test the measurement accuracy and precision, we use a custom-designed gas mixture blender to simulate changes in EE and RQ by a human subject. Using this as a reference criterion, we can develop and optimize algorithms and design (http://www.ncbi.nlm.nih.gov/pubmed/19964185). To test the generalizability of measurements and analysis, we will test and compare two different chamber hardware systems (NIDDK Bethesda vs. University of Colorado Denver).