This observational study aims to collect detailed metabolic and physiologic data from adults with insulin-dependent type 2 diabetes mellitus following consumption of a mixed meal tolerance test. Participants will undergo frequent blood sampling over a 4-hour period after consuming a standardized liquid mixed meal to measure glucose, insulin, glucagon, C-peptide, and triglyceride responses. Participants will also use continuous glucose monitoring and wearable physical activity tracking devices during free-living conditions.

The purpose of this study is to develop mathematical models and digital representations ("digital twins") of people with type 2 diabetes mellitus. These models may help researchers better understand metabolic responses to meals, physical activity, and diabetes treatments, and may support future development of personalized diabetes technologies and therapies.

Participants will first complete a screening visit at the Clinical Nutrition Research Center (CNRC) at the Illinois Institute of Technology. Screening procedures include assessment of medical history, dietary habits, physical activity history, body measurements, vital signs, glycated hemoglobin (HbA1c), and evaluation of eligibility criteria. Eligible participants will receive a continuous glucose monitor (CGM) and wearable activity tracker and will complete dietary recall assessments during the outpatient monitoring period.

Participants will undergo approximately 8 days of outpatient monitoring using continuous glucose monitoring and wearable physical activity tracking devices during free-living conditions. During this period, participants will continue their usual diabetes management and daily activities while recording dietary intake and medication use.

Participants will then complete an in-clinic Liquid Meal Test (LMT) visit following an overnight fast. During the study-day visit, an indwelling intravenous catheter will be placed for repeated venous blood collection. Blood samples will be collected before and over a 4-hour period after consumption of a standardized liquid meal consisting of vanilla-flavored Ensure®. Plasma measurements will include glucose, insulin, glucagon, C-peptide, and triglycerides. Participants will remain seated and monitored throughout the study visit, and safety assessments will be performed before discharge.

The information collected from continuous glucose monitoring, wearable activity tracking, dietary assessments, and repeated blood sampling will be used to develop mathematical models capable of simulating physiologic and metabolic responses in individuals with insulin-dependent type 2 diabetes mellitus. These models may contribute to future research focused on personalized diabetes management, optimization of therapeutic strategies, and evaluation of diabetes technologies.

Inclusion Criteria:

• Men or women, 18-65 years of age
• Diagnosed with insulin-dependent type 2 diabetes mellitus HbA1c ≥ 6.5% at screening
• Current insulin therapy for ≥ 6 months prior to screening
• Nonsmokers (past smokers can be allowed if they have abstained for a minimum of 12 months)
• Judged to be in good health based on medical history (i.e., no clinical evidence of cardiovascular, metabolic, respiratory, renal, gastrointestinal, or hepatic disease)
• Able to provide informed consent
• Able to comply with and perform the procedures requested by the protocol (including dietary restrictions, consumption of study foods, records of food diary, sample collection procedures, and study visit schedule)

Exclusion Criteria:

• Men and women with known or suspected intolerance, allergies, or hypersensitivity to study foods
• Men and women with low hemoglobin (Hgb) levels below 9.5 g/dL at the screening visit, indicating anemia
• Men and women with blood pressure >160 mmHg (systolic) / 100 mmHg (diastolic) at the screening visit
• Women who are pregnant or planning to become pregnant during the study
• Major trauma or a surgical event within 2 months (or longer depending on trauma or event) and after consultation with PI.
• Vegan or other extreme dietary regimens (e.g., Atkins diet, etc.) as judged by the investigator
• History of an eating disorder (e.g., anorexia nervosa, bulimia nervosa, or binge eating) diagnosed by a health professional
• Donated blood within the last 3 months
• Unstable weight: gained or lost weight +/- 5 kg (11 lbs) in previous 2 months
• Unusual working hours i.e., working overnight (e.g. 3rd shift)

Adults 18 to 65 years of age with insulin-dependent type 2 diabetes mellitus will be recruited from the Illinois Institute of Technology Clinical Nutrition Research Center proprietary database, online advertisements, social media, community outreach, and local flyers. Eligible participants must be willing to undergo continuous glucose monitoring, wearable activity tracking, dietary assessment, overnight fasting, repeated blood collection, and a liquid meal tolerance test.