Date of Award

Spring 1-1-2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Integrative Physiology

First Advisor

Matthew B. McQueen

Second Advisor

Monika R. Fleshner

Third Advisor

Robert S. Mazzeo

Fourth Advisor

Kenneth S. Krauter

Fifth Advisor

Jason D. Boardman

Abstract

The obesity epidemic is pervasive across international borders, and the prevalence in children and adolescents is increasing markedly. Recent estimates indicate a global prevalence of 36.8% in males and 38% in females. Obesity is responsible for 3-4 million deaths a year, and is major risk factor for a variety of co-morbidities such as cardiovascular disease, diabetes, and cancer.

Risk of obesity and weight trajectory may be introduced at a very early age. As such, it appears that research into early environmental factors affecting obesity may be most appropriate for developing interventions to reverse the trend of rising prevalence and incidence rates.

One such factor that is studied often and also controversial in obesity research is breastfeeding. Breastfeeding has been thought to have a weak to moderate inverse relationship with weight status. In chapter II, I present original research that investigates the relationship between breastfeeding and body weight in a very large sample of individuals from the Add Health study using both controls for genetic risk of obesity and ancestry. The research also utilized an emerging metric for assigning weight status, the waist-to-height ratio, as the primary outcome.

The waist-to-height ratio has improved diagnostic capability over the body mass index. However, there is not an appropriate cutoff established in a population that would be generalizable to the Add Health study. As the waist-to-height ratio takes waist circumference into account, and waist adiposity is causally related to a variety of adverse cardiometabolic outcome, I conducted a study that establishes sex-specific cutoffs for the waist-to-height ratio that predict metabolic syndrome.

Finally, another factor that has been shown to influence weight is the microbiome. This is relevant to the discussion of early environmental factors as the colonization of the microbiome begins at an early age. As much of this research has been conducted on the gut microbiome, I present research that examines the relationship between the oral microbiome and obesity. This research uses weighted gene co-expression network analysis to establish modules of related bacteria and regression analysis to determine if any of the modules were related to obesity.

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