Date of Award

January 2024

Document Type


Degree Name

Master of Public Health (MPH)


School of Public Health

First Advisor

Debbie Humphries

Second Advisor

Michaela Dinan


Background: The US has seen a consistent increase in obesity rates over the last sixty years across all racial and ethnic groups, with similar trends even among privileged groups. This study examines Macronutrient intake trends in US adults from 1999-2018 and their association with demographic factors: race ethnicity, age, gender, and education.

Methods: We conducted a serial cross-sectional analysis of US adults using 24-hour dietary recall data from 10 NHANES survey cycles (1999-2018). Piecewise regression models identified significant dietary pattern changes over time, by demographic groups. Statistical analysis was done in R and SAS utilizing NHANES sampling weights.

Results: Study sample included 50,666 respondents. Average BMI significantly increased from 28 to 30 (p<0.001). From 1999 to 2018, estimated energy intake from saturated fat increased from 10.91% to 11.89% (increase in ~8.77 kcal, p < 0.001), with higher increase in intake among those with higher education and older age. Protein intake increased from 15.46% to 15.80% (increase of ~9.67 kcal, p=0.029), with variations across age groups. Carbohydrate intake decreased from 50.36% to 46.27% (reduction of ~136.83 kcal, p<0.001), particularly among those with higher education and older age.

Conclusion: From 1999 to 2018 dietary intake of U.S. adults had increased saturated fat intake and decreased carbohydrate consumption. Trends varied by education level and age, and older adults and more educated participants had higher saturated fat intake and reduced carbohydrates. The study emphasizes the limitations of reductionist dietary approaches and advocates for holistic, food-based interventions in public health and nutrition.


This thesis is restricted to Yale network users only. It will be made publicly available on 05/07/2026