Obesity and metabolic syndrome are common problems that are both associated with reductions in lung function, although the mechanisms remain poorly understood. These conditions may also be linked to the development of asthma and chronic obstructive pulmonary disease (COPD). However, obesity can make it more difficult to diagnose airways disease using spirometry. This project will investigate links between obesity, insulin-resistance and airways disease. Data from a large New Zealand cross-sectional study will be analysed to derive spirometric equations that take account of weight. These will be used to analyse lung function test results from obese patients to improve the accuracy with which airways disease is diagnosed in this population. A cross-sectional study will examine relationships between COPD and the metabolic syndrome in non-smokers who develop COPD. Finally, a prospective pilot study will examine the effects of metformin on lung function in subjects with COPD and impaired glucose tolerance.