Award Date
May 2025
Degree Type
Thesis
Degree Name
Master of Science (MS)
Department
Kinesiology and Nutrition Sciences
First Committee Member
Sara Rosenkranz
Second Committee Member
Laura J. Kruskall
Third Committee Member
Neda Akhavan
Fourth Committee Member
Christopher Johansen
Number of Pages
76
Abstract
Background: Understanding postprandial metabolic responses to nutritional inputs is important for developing effective dietary recommendations and preventing chronic diseases. While between-person variability in postprandial glucose and lipid responses is well studied, within-person variability is not fully understood. Lifestyle factors such as dietary quality, physical activity, sleep, and stress, may contribute to this variability. This study aimed to investigate within- and between-person variability in postprandial glycemic and lipidemic responses to high-carbohydrate and high-fat meals, and to explore associations between lifestyle behaviors and postprandial responses. Methods: Twenty participants were randomized to a high-carbohydrate or high-fat meal condition, where the assigned meal type was consumed at three separate timepoints. Eleven participants completed both conditions in a crossover design. Dietary quality was assessed using the Healthy Eating Index based on three 24-hour dietary recalls collected via the Automated Self-Administered 24-Hour (ASA-24®) Dietary Tool. Physical activity was assessed using Activities Completed over Time in 24 Hours (ACT-24) recalls and International Physical Activity Questionnaires (IPAQ), while sleep quality was evaluated through the Pittsburgh Sleep Quality Index (PSQI) and stress levels using the Depression, Anxiety, and Stress Scale-21 (DASS-21). Physical activity was also objectively measured using accelerometry (Fibion SENS). Continuous glucose monitors (Dexcom G7) recorded postprandial glucose at 0, 15, 30, 60, 90, and 120 minutes, while blood lipids were assessed via fingersticks at 0, 120, and 240 minutes. Incremental area under the curve (iAUC) was calculated using the trapezoidal rule. Intraclass correlation coefficients (ICCs) were used to compare within- and between-participant variability. Results: The ICCs revealed substantial within-person variability in metabolic responses, particularly after high-carbohydrate meals. For the high-carbohydrate meal condition, lower and negative ICC values (-0.171 for single measures and -0.412 for average measures) with 95% confidence intervals ranging from -0.603 to 0.339 and -3.040 to 0.507 respectively, suggested that individual responses were highly inconsistent across different time points, with between-person differences contributing minimally to the overall variance. This was further supported by the non-significant F-test for reliability (F = 0.708, p = 0.744). Following the high-fat meal, glucose iAUC values ranged from 0.0 to 4507.5 mg/dL × 2 h and TG iAUC values from 340.0 ± 588.9 to 12,960.0 ± 4817.9 mg/dL × 4 h. There was significant between-person variability in glucose (p = 0.002), but not TG (p = 0.68) following the high-fat meal. Poorer sleep quality was associated with lower glucose responses (rho = -0.509, p = 0.004). Conclusions: Findings highlight the importance of considering within-person variability as compared to the current popular focus on between-person variability. The observed heterogeneity in metabolic responses suggests the need for repeated measurements to improve individualized dietary recommendations.
Disciplines
Nutrition
Degree Grantor
University of Nevada, Las Vegas
Language
English
Repository Citation
Shahamati, Donya, "Within and Between-Person Variability in Glycemic and Lipidemic Responses to High-Fat and High-Carbohydrate Meals" (2025). UNLV Theses, Dissertations, Professional Papers, and Capstones. 5330.
https://oasis.library.unlv.edu/thesesdissertations/5330
Rights
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