The major purpose of this research project is to learn if consuming artificial sweeteners have any impact on glucose levels in adults at high risk for developing type 2 diabetes. People may be at risk for diabetes if you are a middle-aged or older adult. Briefly, the full study is 3 weeks long with 3 controlled feeding visits. Which means participants will eat all of the food and drinks that we provide to them for breakfast. Participants will come to the lab in the morning to eat breakfast, and we will monitor changes in blood glucose over a 2 hour period. Participants will be randomized into 1 of 3 groups: 1 group will receive aspartame (Equal), 1 group will receive sucralose (Splenda), and 1 group will receive no artificial sweeteners. Participants will experience a different group each visit, with about 7 days between each visit. We will be examining if consuming artificial sweeteners has any impact on glucose levels.

The study will utilize a randomized 3 period crossover design, with 3 instances of controlled feeding. The overall objective of this study is to establish proof-of-concept for impaired glycemic control and insulin sensitivity, but no alterations following aspartame intake, in middle-aged/older adults with prediabetes. We aim to enroll 14 middle-aged/older adults (40+ years) with prediabetes. Participants will be randomly assigned to 1 of 3 controlled feeding conditions for 3 separate visits: sucralose (Splenda), aspartame (Equal), or control, each separated by a week. All participants will have been assigned to each artificial sweetener once by the end of the study. All test conditions will receive an identical breakfast, with the exception of the sweetener type. Glucose tolerance and insulin sensitivity will be measured directly after each controlled feeding.

Inclusion Criteria:

• Age 40+ years
• Prediabetic
• Weight stable for previous 6 months
• BMI <40 kg/m2
• Sedentary to recreationally active
• No plans to gain/lose weight or change physical activity level
• Consume less than one serving of non-sugar sweeteners per week

Exclusion Criteria:

• Diabetes or any diabetes medications
• Antibiotic, prebiotic or prebiotic use in prior 3 months
• Blood pressure (BP) > 159/99 mmHg
• Change in type or dose of these prescription medications over the past 6 months: antihypertensive medications, Statins, hormone replacement therapy (estrogen or testosterone) or oral contraceptives, thyroid medications
• Diagnosed inflammatory bowel disease
• Past or current heart diseases, stroke, respiratory disease, endocrine or metabolic disease, or hematological-oncological disease
• Vegetarian or vegan
• Pregnant or plans to become pregnant
• Breastfeeding
• Food allergies or aversions, Phenylketonuria (PKU)