Three essays on nutrition and health: sugar-sweetened beverages, postpartum military wellness, and online grocery shopping

Abstract

This dissertation comprises three distinct, yet interconnected essays on nutrition and health, exploring behavioral and policy factors that shape and influence nutrition status, food choices, and health outcomes. The first chapter presents a structural model based on the socioecological theory to define how behavioral strategies, health literacy, and the interconnected decision-making process of children and their caregivers simultaneously affect children's sugar-sweetened beverage (SSB) consumption. Using this framework, the study evaluates the Kids SIPsmartER (KSS) program, a school-based intervention designed to reduce SSB consumption among middle-school students. KSS directly targeted students (KSS-S) through health literacy and behavioral strategies grounded in the Theory of Planned Behavior, and engaged caregivers (KSS-C) in limiting their children's SSB intake. We employ structural equation modeling to evaluate the effectiveness of the dual KSS interventions in targeting the mediating pathways of behavioral responses, health literacy, and caregiver influence. We found that KSS-S treatment leads to a total reduction of 6.42 oz/day (p<0.05) primarily through a direct, significant partial effect. The KSS-C yields a statistically insignificant decrease in student consumption by 4.22 oz/day (p = 0.26), largely through the caregiver's decision. Combined, KSS reduced SSB consumption by 10.64 oz/day (p<0.01) over 7 months. The findings of this causal pathway analysis can inform improved targeted dyadic SSB intervention design in reducing children's SSB intake. The second essay examines the impact of pregnancy and excessive gestational weight gain (eGWG) on physical fitness among active duty United States Air Force (USAF) servicewomen. Active duty members of the USAF must undergo regular physical fitness assessments, with repeated failures potentially leading to separation from service. Weight gain is a particular concern, as excess weight and inadequate fitness are common reasons for discharge. The risk presents a unique challenge for postpartum military servicewomen. Using propensity score matching/weighting with difference-in-differences regression models, we find that pregnancy is associated with a 2.3-2.6% (p<0.01) decline in physical fitness assessment pass rates and a reduction of 1.46-1.62 points (p<0.01) in composite test scores. eGWG is associated with a 2.01- 2.05-point reduction in test scores (p<0.05) and a 7.20% increase in any component exemption (p<0.05). These results underscore the importance of targeted interventions, such as tailored postpartum fitness programs, enhanced prenatal weight management strategies, and greater awareness through education campaigns for pregnant USAF servicewomen. The third essay investigates the socioeconomic determinants of online grocery shopping adoption and usage patterns among consumers in the United States. We employ a multivariate probit model to examine three interrelated dimensions of online grocery shopping: (1) the decision to shop for groceries online, (2) the primary reason for shopping online, and (3) the frequency of online purchases, within a utility maximization framework. By characterizing the various reasons for online grocery shopping as Lancaster attributes, we analyze how the frequency of online grocery shopping is determined by the consumer's choice of their most preferred attribute. The results show that at the extensive margin, adopters of online grocery shopping are more likely to be younger, more educated, female, have eldercare responsibilities, and live in households with children under 18 years. However, individuals residing in areas with low food store access are less likely to use online grocery services. At the intensive margin, consumers who shop online primarily for price/product-related reasons tend to make fewer online purchases. While older consumers are less likely to shop online, they use online services more frequently at the intensive margin. These findings point toward opportunities for policies to promote healthier food choices on online platforms, enhance transparency regarding prices and products, and introduce interventions to remove barriers to adoption. Together, these essays contribute to the literature on nutrition programs, food choices, and health policies encompassing diverse populations, including middle-school students, military servicewomen, and the average American household. These essays offer evidence-based insights for targeted interventions to address distinct health and nutrition challenges of each of these population segments.