All ETDs from UAB

Advisory Committee Chair

Jose R Fernandez

Advisory Committee Members

Jamy Ard

Ambika Ashraf

Timothy M Beasley

Molly S Bray

Sasanka Ramanadham

Document Type

Dissertation

Date of Award

2011

Degree Name by School

Doctor of Philosophy (PhD) School of Health Professions

Abstract

Energy balance exists when intake is equivalent to expenditure. It has become evident that beyond quantitative aspects of intake, dietary components also have directive impact. On the expenditure side, an underappreciated yet key contributor is resting energy expenditure (REE). As the largest constituent of overall energy output, REE encompasses physiologic, dietary and genetic influence on body composition. While cellular and overall systemic contribution cannot be ignored, the relative proportion of adipose, bone and lean body tissue (i.e., body composition) represents the primary determinant underlying REE. It is possible that the mineral calcium is a common denominator encompassing energy balance influenced by diet while influencing tissue maintenance, with an active role in regulating tissue metabolism, as well as in cellular and systemic function comprising REE. Despite the substantial contribution of REE to overall energy balance, underlying factors which alter energy utilization pathways at rest remain relatively unexplored, with investigations centered on growth and development even more limited, a time particularly influential in terms of long-term body composition trajectory. In a multi-ethnic sample of peri-pubertal children (n=315), three specific aims were investigated. Investigation of the first specific aim to determine associations among calcium intake, REE and body fat indicated (as opposed in part to that which was hypothesized) that REE mediated a positive relationship between calcium intake and body fat, providing support for effects of calcium intake on body composition. The second specific aim to identify associations between calciotropic hormonal factors and body composition with REE indicated increased intake of calcium-related nutrients and decreased circulating calciotropic hormone PTH were associated with higher REE. The third specific aim to evaluate relationships of REE with genetic polymorphisms having been shown to influence calcium regulation, indicating adiposity- and ethnic-specific associations with vitamin D receptor genotype, whereas sex and calcium intake seem to influence that between REE and calcium-sensing receptor genotype. Taken together, regulatory factors exerting effects on the calciotropic network are associated REE and may manifest as alterations in body composition. These findings support the importance of dietary nutrient adequacy for optimal allocation of energy for growth with potential long-term implications.

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