Almost half of adults in the United States have either diabetes mellitus (DM) or prediabetes (preDM), but many are undiagnosed and unaware of their condition. Current DM diagnosis and risk prediction are based on single "snapshot" measurements including: fasting blood glucose, postprandial glucose, and hemoglobin (Hb)A1c. Continuous glucose monitoring (CGM) offers a dynamic view of glucose levels throughout the day which enables characterizing individuals' dynamic glycemic profiles in response to physiological and environmental stimuli better than the conventional point-in-time glucose quantification approaches. By analyzing glycemic patterns from CGM tracings, it may be possible to identify individuals at increased risk of developing diabetes. However, an important prerequisite is to establish the reliability and consistency of glucose response patterns captured by CGM under controlled conditions.

Participants will be given six different meals to examine the glucose responses to these meals. Two of these meals (white rice and an Ensure drink) will be given twice for each participant to investigate whether individuals have the same glucose response to the same meal given on different days. Glucose will be measured using continuous glucose monitors, that have a thin wire sensor that measures glucose under the skin every five minutes for up to 10 days.

This is a pilot study in which each participant undergoes six meal challenges (one each morning) under free-living conditions, while wearing a blinded CGM sensor. Glucose levels will be continuously measured, and meal challenge sequence will be randomly assigned to each participant.

The study objectives are to:

1. determine the within meal replicability of postprandial glucose response to a Ensure and White Rice meal challenges
2. evaluate if a whole food meal challenge (White Rice) exhibits lower reliability and greater physiological variability (under the chewing vs. not chewing condition) in postprandial glucose response compared to a standardized liquid mixed meal tolerance test (Ensure)
3. compare the postprandial average peak glucose response and 4 hour incremental area under the curve (iAUC) for the Ensure tolerance test, mountain dew tolerance test, White Rice, and typical breakfast.

These findings will inform the design of future studies and the potential use of CGM-based dietary challenges for early detection of metabolic risk.

Inclusion Criteria:

• Generally healthy
• English speaking

Exclusion Criteria:

• Prior diagnosis of diabetes or taking medications that influence glucose metabolism, such as insulin, glucocorticoids, or Glucagon-like peptide-1 (GLP-1) receptor agonists.
• Taking hydroxyurea medication
• Taking beyond the maximum dose of acetaminophen (4g/day)
• Known food allergies or severe sensitivities to any study materials (dairy or soy)
• Limited and non-readers
• Cognitive impairment