We will enroll 24 NW and 24 obese (OB) participants. Half of the NW and OB groups will be PPI users and half will be non-users of acid suppressing medications. The primary outcome for Aim 1 is the difference in the PRA of Firmicutes and Bacteroidetes. A two-way ANOVA (factors of BMI category and PPI use) will be used. Based on our preliminary data, we will have 94% power to detect a difference in the PRA of Firmicutes (72% vs 52% with SD of 20%) and 95% power to detect differences in the PRA of Bacteroidetes (16% vs 5% with SD of 5%) between PPI users and non-users. The primary outcome for Aim 2 is the difference in bacterial RNA dedicated to the fermentation cycle while the outcome for Aim 3 is the difference in expression of GPR 41 and GPR 43. Based on the expected differences in the gut microbiota profile and subsequent SCFA production, we expect a 25% difference between PPI users and non-users for both outcomes, giving us 99% power for both Aims 2 and 3). We will also perform subgroup analyses within the NW and OB groups.