Comparative Analysis of Plant-Based and Omnivorous Diets on Lipid Profiles

Thesis Abstract

This study investigates whether plant-based and omnivorous dietary patterns produce differential lipid profiles among adults, addressing the rising prevalence of dyslipidemia and the need for actionable dietary guidelines within diverse populations. The aim is to compare lipid outcomes across dietary patterns while accounting for confounding factors such as age, sex, BMI, physical activity, and socioeconomic status. Specific objectives include (1) estimating mean levels of total cholesterol, LDL-C, HDL-C, and triglycerides among individuals adhering predominantly to plant-based versus omnivorous diets; (2) evaluating the association between diet type and lipid markers after adjusting for covariates; (3) examining the dose–response relationship between plant-based diet adherence (measured by a validated plant-based diet index) and lipid outcomes; and (4) exploring potential effect modification by sex and BMI category. The study adopts a cross-sectional design conducted in an urban setting with adults aged 25–65 years. A stratified random sample of 600 participants (300 plant-based adherents and 300 omnivores) is recruited from community centers, primary care clinics, and university-affiliated networks to ensure representation across socioeconomic strata. Data collection employs a validated dietary intake instrument (a semi-quantitative food frequency questionnaire tailored to regional foods) to categorize diet type and quantify plant-based diet adherence, alongside anthropometric measurements, fasting blood samples, and structured questionnaires capturing demographic, lifestyle, and medical history variables. Lipid profiles, including total cholesterol, LDL-C, HDL-C, and triglycerides, are measured using standardized enzymatic assays in accredited laboratories, with quality control procedures and duplicate measurements to ensure reliability. Statistical analyses proceed in three stages descriptive statistics to characterize the sample by diet group, bivariate analyses to identify initial associations, and multivariable regression modeling to assess the independent effect of diet type on each lipid outcome. Regression models adjust for age, sex, body mass index, physical activity (assessed by a validated questionnaire), smoking status, alcohol intake, caloric intake, and presence of comorbidities. Where appropriate, log transformation is applied to skewed lipid variables, and interaction terms test for potential effect modification by sex and BMI category. In addition, a sensitivity analysis using propensity score weighting mitigates residual confounding. The study anticipates observing lower mean LDL-C and total cholesterol and higher HDL-C among plant-based adherents, with triglyceride differences more nuanced depending on fat quality and dietary patterns. The magnitude of associations is expected to be modest but clinically meaningful, particularly for individuals at elevated baseline risk for cardiovascular disease. The findings are anticipated to contribute to knowledge by clarifying the lipid-related health implications of plant-based versus omnivorous diets within a real-world adult population, informing dietary recommendations and public health strategies aimed at dyslipidemia prevention. The study advances theoretical understanding by integrating the dietary pattern framework with lipid metabolism paradigms and supporting the relevance of the plant-based diet index as a practical exposure measure in nutritional epidemiology. Implications for practice include reinforcing dietary counseling that emphasizes whole-food plant sources, reduced saturated fat intake, and overall dietary quality to optimize lipid profiles. Potential limitations include the cross-sectional design limiting causal inference, possible residual confounding, and reliance on self-reported dietary data. The authors address these constraints through rigorous statistical adjustment, multiple sensitivity analyses, and transparent reporting of measurement error. Overall, the research aims to provide robust, generalizable evidence on how plant-based versus omnivorous dietary patterns relate to lipid health, offering direction for future longitudinal and interventional studies to establish causality and inform tailored nutrition guidance.