We will recruit 15 healthy, overweight volunteers, age 18-35. Each subject will receive 4 interventions: an oral glucose challenge 1) with and 2) without 0.1% benzoic acid, and a drink of water 3) with and 4) without 0.1% benzoic acid. Blood samples will be analyzed for glucose, insulin, glucagon, and a panel of approximately 300 different metabolites at baseline and serially for 2 hours after each intervention. Factorial analysis of variance will be performed to determine the effects of benzoic acid in the presence and absence of glucose, and interactions between glucose and benzoate. The planned sample size of 15 will provide 80% power to detect an effect-size of 0.16 standard-deviations in outcome measures, and an interaction-effect of 0.33 standard-deviations, with a critical value p=0.05.