Diabetes, impaired glucose tolerance and the metabolic syndrome are all associated with a modest restrictive lung defect. There appears to be a dose-response relationship between increasing numbers of components of the metabolic syndrome and the degree of impairment of pulmonary function. Possible underlying mechanisms include glycation of structural proteins within the thorax, the mechanical effects of visceral adiposity, and chronic inflammation. Spirometry as part of usual care may be an inexpensive and efficient way of identifying patients at increased cardiopulmonary risk and as a prognostic marker of all-cause mortality. © 2014 JOHN WILEY & SONS.