The purpose of this research study is to examine whether sugar-replacement sweeteners that are currently on the market (ex. Sucralose, which is in Splenda) change how well the body works to control blood sugar.

The investigators of this study have recently found that sucralose, the most commonly used non-nutritive sweetener (NNS), affects the glycemic response to an oral glucose tolerance test (OGTT) and potentiates glucose-stimulated insulin secretion in obese people who are not regular consumers of NNS. However, studies conducted in healthy lean adults, none of which control for previous use of NNS, show that sucralose does not affect glycemic or hormonal responses to the ingestion of glucose or other carbohydrates. Therefore, we do not know a) whether sucralose effects are limited to obese subjects, or are generalizable to lean people when controlling for prior history of NNS consumption, and b) mechanism(s) responsible for the acute effect of sucralose on glucose metabolism as we measured in obese subjects. The aim of this study is to determine the effects of an acute intake of sucralose on the metabolic response to an oral glucose tolerance test in lean and obese people.

Inclusion Criteria:

• BMI ≥ 30 kg/m2 or BMI ≥ 18 kg/m2 and BMI<25 kg/m2
• "insulin sensitive": based on the homeostasis model assessment of insulin resistance (HOMA-IR) <3

Exclusion Criteria:

• BMI ≥ 25 kg/m2 and BMI<30 kg/m2
• HOMA-IR>3
• Current smoker or quit smoking less than 6 months ago
• pregnancy or breastfeeding
• subjects who have malabsorptive syndromes, phenylketonuria, inflammatory intestinal disease, liver or kidney diseases, diabetes
• subjects who are taking any medication that might affect metabolism
• anemia
• regular use of non-nutritive sweeteners