Energy Expenditure and Substrate Utilization in Obese Individuals with Heart Failure

Abstract

NURSING SCIENCE

ENERGY EXPENDITURE AND SUBSTRATE UTILIZATION IN OBESE INDIVIDUALS WITH HEART FAILURE

JOSHUA PHILLIP SQUIERS

Dissertation under the direction of Professor Michael Vollman Heart failure (HF) is a severely limiting terminal illness that affects over 5.7 million Americans per year. Changes in body composition during the course of HF appear to significantly affect morbidity and mortality. Little is known, however, regarding the systemic level energetics that lead to body composition changes and subsequent changes in morbidity and mortality. The purpose of this cross-sectional, exploratory study was to determine the feasibility of using 24 hour whole room indirect calorimetry in the HF population, and to provide an initial description of resting energy expenditure and substrate utilization differences between healthy obese individuals and obese patients with ischemic HF (N = 10). Five obese HF subjects were recruited and five healthy obese control subjects were selected from the Vanderbilt University’s Energy Balance Laboratories calorimetry database. The five HF subjects were admitted for a 24 hour whole room calorimetry, including measurement of resting energy expenditure and substrate utilization, body composition, anthropometric measures, and were compared against the five control subjects. Results from this study suggest that obese HF patients have a 16.6% increase in REE (0.0267 vs. 0.0223 kcal/min/kg LM, p = 0.08) and a lower RQ (0.738 vs. 0.898, p = 0.043) compared with healthy obese individuals. These results from this limited research sample suggest that there is an increasing metabolic demand associated with HF, along with a preference toward fat metabolism at rest. Feasibility was confirmed with each subject providing more than 90% of analyzable calorimetry data during a 24 hour measurement period. Whole room indirect calorimetry provides a novel, highly accurate technique for future examination of substrate and systemic energetic questions related to the HF disease process. Further research is needed to clarify the effects of changes in REE and RQ in patients with HF. Ultimately, providing an accurate description of the energetic cost of HF, and the mechanisms behind these costs may lead to potential clinical interventions to improve morbidity and mortality.