Abstract: The purpose of the Military Health and Nutrition Examination Study (MHANES) is to assess dietary intake, cardiometabolic health, body composition, nutritional status and health biomarkers, mental wellbeing, injury prevalence, genetics, gut microbiome composition, and physical performance in a large, diverse, representative sample of active-duty Service Members (SMs). MHANES is modeled after the National Health and Nutrition Examination Survey (NHANES), which does not enroll active-duty SMs. NHANES data are not generalizable to active-duty SMs since they are often exposed to unique and more adverse occupational challenges than civilians. MHANES will recruit active-duty SMs (n=600) from Army installations across the US. Participants will attend one in-person visit to complete a 24-hour dietary recall and questionnaires regarding demographics, physical and mental health, and dietary supplement and prescription drug use. Height, weight, blood pressure, resting heart rate variability via a chest-worn device, physical activity and sleep via actigraphy, and resting metabolic rate via indirect calorimetry will be measured. Body composition will be measured by bioelectrical impedance, 3D body imaging, and circumference measurements. Blood and urine will be collected to measure health and nutrition biomarkers and genetics. Stool samples will be collected to measure microbial diversity and composition. A second 24-hour dietary recall will be administered 3-10 days later. Data collected will be used for determination of disease risk and prevalence and to investigate relationships between dietary intake, nutritional status, and various markers of health and disease in active-duty SMs. Findings will guide evidence-based screening, education, intervention strategies, and policy decisions to improve military health.