Diabetes patients often fail to adhere to self-management activities, such as losing weight by exercising and dieting. The present study tested the efficacy of a minimalist intervention consisting of only the self-regulation strategy 'mental contrasting' (Oettingen, G. (2000). Expectancy effects on behavior depend on self-regulatory thought. Social Cognition, 18, 101-129) in promoting these self-management activities among a clinical sample of type 2 diabetes patients (N = 64). Half of the participants were assigned to a positive indulging condition (fantasising about positive outcomes of losing weight) and the other half of the participants were assigned to a mental contrasting condition (fantasising about positive outcomes of losing weight and then contrasting these fantasies with obstacles in the present reality). Results showed that, one month later, participants in the mental contrasting condition had improved their diabetes self-management, and in particular their dieting behaviour, by a larger extent than participants who merely indulged in the positive future. It was concluded that although more elaborate interventions may yield stronger results, adding a mental contrasting exercise to their usual care may be a highly feasible, low-cost alternative to promote diabetes self-management.