This study will compare two approaches to the measurement of fatty acid oxidation (ketone body flux and ketone body concentration) and determine which method demonstrates superior sensitivity and variability in the detection of moderate increases in ketogenesis rates.

Inclusion Criteria:

• Subject has a Body Mass Index of 18-25 kg/m2 OR 29-40 kg/m2
• Subject has been a nonsmoker or has not used nicotine for the past 6 months

Exclusion Criteria:

• Subject has a history of diabetes mellitus
• Subject has a history of stroke, chronic seizures, or other neurological disorder
• Subject has a history of cancer, except certain skin cancers
• Subject consumes more than 3 alcoholic beverages per day
• Subject consumes more than 6 servings of caffeinated beverages per day
• Subject has multiple and/or severe allergies to food or drugs
• Subject has allergy or sensitivity to eggs or soy
• Subject regularly uses illicit drugs or has a history of drug or alcohol abuse