A novel scoring method to evaluate associations between dietary variety and body adiposity in a national sample of U.S. adults

Obesity and its associated metabolic consequences are a major public health concern in the U.S. Population-level strategies to reduce body adiposity while optimizing the nutritional health of the nation are urgently needed. Since the inception of the Dietary Guidelines for Americans, dietary variety has been a key component of these recommendations because of its associations with improved nutrient intake. However, as the food landscape in the U.S. has changed, this recommendation has been eliminated as a separate entity based on evidence that consumption of a greater number of foods increases energy consumption. Despite growing concern about dietary variety encouraging overconsumption and obesity, the tools available to measure this construct have failed to adapt to changing food environments. Therefore, it is not possible to accurately evaluate the associations between dietary variety and excess adiposity in large population studies. Consequently, across four chapters, this dissertation describes:1) the need for a novel food diversity index, 2) the development of the U.S. Healthy Food Diversity (HFD) index, 3) the validation of the U.S.HFD, and 4) the associations between the U.S.HFD and body adiposity within a nationally-representative U.S. sample. U.S.HFD development was necessitated by the inability to concurrently measure dietary variety, dietary quality, and proportionality, which is integral for the formulation of dietary variety recommendations that promote energy balance and health. Next, in order to ensure that the U.S.HFD captured its intended dimensions, it was evaluated for reliability and validity. These analyses demonstrated that higher scores corresponded with more healthful, varied dietary patterns and that the index discerned between populations with established differences in dietary quality. Finally, the associations between the U.S. HFD and measures of body adiposity were evaluated. This study demonstrated that greater variety within healthful foods may confer protection against many measures of excess adiposity in a nationally-representative sample. Collectively, this dissertation provided foundational evidence that dietary variety may be an overlooked strategy to improve population health and explicitly recognized the benefits of healthful food variety in weight control. The dissertation establishes a framework for future investigation into the role of dietary variety in managing the weight of the nation.