Thirty-five individuals with extreme obesity (body mass index or BMI = 50 +/- 8 kg m((-2)) and 26 fit, non-obese subjects (BMI = 23 +/- 2 kg m((-2)) participated. DLNO and DLCO at rest were first measured. Then, subjects performed a graded exercise test on a cycle ergometer to determine (VO2peak). Multivariate regression was used to assess relations in the data.