Plasminogen activator inhibitor 1 (PAI-1) is elevated in obese individuals with type 2 diabetes and may contribute, independently of traditional factors, to increased cardiovascular disease risk. Fiber intake may decrease PAI-1 levels. We examined the associations of fiber intake and its changes with PAI-1 before and during an intensive lifestyle intervention (ILI) for weight loss in 1,701 Look AHEAD (Action for Health in Diabetes) participants with dietary, fitness, and PAI-1 data at baseline and 1 year.