Whole body energy expenditure, measurement

In a recent patent application, mice treated with a related iron chelator, deferasirox (DFS), showed reduced body weight while on a high fat diet compared to untreated controls. Additionally, DFS was claimed to improve whole body metabolism and energy expenditure as measured by increased 02 consumption and C02 production as well as a reduction in white adipose and visceral fat, despite little difference between food intake in the control and treated animal groups [25]. 

At the level of the whole body, the two most practical methods of measuring energy expenditure are indirect calorimetry and the nse of doubly labeled water. 

Another goal of the USDA study was to determine whether CLA enhanced energy expenditure, lipolysis, or fat oxidation in humans, similar to the effects observed in animals. Accordingly, measurements of metabolic rate and respiratory quotient were made by indirect calorimetry, and stable isotope tracers of palmitate and glycerol were used to measure the rate of appearance of free fatty acids and glycerol as well as whole body lipolysis and apparent reesterification. CLA supplementation had no effect on metabolic rate or whole-body fat oxidation rate during rest or exercise. Similarly, CLA did not change lipolytic rate, fatty acid release from adipose tissue, or apparent FFA reesterification rates under conditions of rest or exercise (33). 

The characterization of energy balance in cells and tissues relies upon the measurement of several variables oxygen and substrate consumption, lactate and carbon dioxide production. These measurements however give only indirectly and partly quantitative information about the energy balance in obesity. Whole body calorimetry and direct measurement of cell heat production have been introduced as a complement to the assessment of energy balance in the whole organism and energy expenditure on the cellular level. 

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