Variability In Mixed Meal Tests: Fixed Versus Adjusted to Energy Needs Caloric Dose

Background: Researchers use mixed meal tolerance tests (MMTTs) to look at how people s bodies respond to eating a meal. However, researchers do not agree on how to decide the number of calories to give in each meal. Some use fixed meals, which are the same size for everyone, and some use adjusted meals, based on the size of the person s body. Researchers want to know which MMTT is best to use for future research. Objective: To learn how fixed vs adjusted meals affect blood glucose levels in healthy people. Eligibility: Healthy people aged 18 years or older. Design: Participants will have 3 or 4 clinic visits of up to 8 hours in 8 weeks. Participants will have baseline tests: Their height, weight, and waist size will be measured. They will have an oral glucose tolerance test: A needle attached to a tube (IV) will be inserted into a vein in the arm. They will have a sugary drink. Blood samples will be taken from the tube at intervals up to 3 hours after the drink. They will have a body scan. Participants will have 2 MMTT visits. One will include a fixed meal and one will include an adjusted meal. They will have tests at both visits: Resting metabolic rate: A clear hood will be placed over the participant s head while they rest for 20 minutes. This will measure the oxygen they breathe in and out. MMTT. Participants will have 5 minutes to drink a liquid meal. Blood samples will be taken at intervals for the next 4 hours....

Study Description: This study will be an outpatient study completed in 3-4 separate visits. We will compare two methods of dosing (fixed and adjusted) a mixed meal tolerance test (MMTT) to determine which results in greater physiological variability in hormone response. Ultimately, the goal is to determine which method of dosing is more appropriate in a research setting. Objectives: Primary Objective: To determine whether an adjusted energy dose MMTT or a fixed dosed meal will result in greater variability in glucose area under the curve (AUC) within the same participants across a range of BMIs. Secondary Objectives: To determine whether baseline body composition, blood parameters (lipids, hormones, etc), and resting metabolic rate are associated with MMTT responses and whether this association is moderated by MMTT condition (fixed vs. adjusted). Endpoints: Primary Endpoint: Glucose area under the curve (AUC) Secondary Endpoints: Area under the curve (AUC), incremental area under the curve (iAUC), value and timing of the absolute maximum (peak), value and timing of the inflection point after the absolute maximum value, value and timing of the maximum rate of incline, value and timing of the maximum rate of decline, total number of critical points with body composition, blood parameters, and resting metabolic rate as predictors.