Effect of smoking on hemoglobin A1c and body mass index in patients with type 2 diabetes mellitus.

Background: Smoking is associated with a decrease in body weight in patients without diabetes mellitus and an increase in insulin resistance and hemoglobin A1c (HbA1c) levels in patients with type 1 diabetes mellitus. Whether smoking is associated with an increase in HbA1c and/or a decrease in body mass index (BMI) in type 2 diabetes mellitus is unresolved, however. Therefore, the objective of this study was to determine the effect of smoking on HbA1c levels and BMI in a cross-section of outpatients with type 2 diabetes mellitus.