The study is designed to test the following experimental hypotheses:[13C]-pantoprazole pharmacokinetic parameters are not different between non-obese and obese children and adolescents, collectively (both age groups combined) or stratified by age group (SA 1) [13C]-pantoprazole pharmacokinetic parameters or DOB values (and thus, CYP2C19 activity) are not different between males and females (SA 1 & 2) [13C]-pantoprazole pharmacokinetic parameters and DOB (Delta over baseline) values (and thus, CYP2C19 activity) are independent of age over the age range of 6 to 17 years (SA 1 & 2) Obesity does not alter the relative contributions of CYP2C19-dependent and non-CYP2C19-dependent (i.e., CYP3A4) metabolism of pantoprazole, as measured by the urinary ratio of 4-hydroxy-pantoprazole to pantoprazole sulfone (SA 1 & 2) The [13C]-pantoprazole breath test, by determining DOB at discrete time point(s), is a non-invasive measure of CYP2C19 phenotype (SA 2) Clearance of pantoprazole (surrogate for CYP2C19 activity) is a function of REE in obese and non-obese children and adolescents (SA 3) Pantoprazole clearance (surrogate for CYP2C19 activity) is associated with fat distribution, as determined by waist-to-hip ratios (SA 3)