Since April 2008, Japanese insurers are obligated to implement a programme to prevent lifestyle related diseases consisting of annual health checks, which screen for Metabolic Syndrome (MetSyn) and health guidance programmes, which aim to induce behaviour modification to prevent lifestyle related diseases. The programme is based on the assumption that visceral fat is a risk factor for MetSyn, which is a risk factor for lifestyle related diseases. Therefore, the programme focuses on the prevention of obesity, but this involves several aspects, which are ethically questionable. In this essay, I use the ethical framework for the prevention of overweight and obesity introduced by Marieke ten Have et al. (2012) to analyse ethical aspects of the Japanese programme to prevent lifestyle related diseases. The framework takes into consideration how a programme affects physical health, psychosocial well-being, equality, informed choice, social and cultural values, privacy, the attribution of responsibilities and liberty. Following this framework I show ethical pitfalls of the Japanese programme to prevent lifestyle related diseases, which are mostly due to an oversimplification of obesity and its causes and consequences. It is likely that the programme has negative effects on the physical and psychosocial well-being of the participants as it may reinforce stigma and lead to eating-disorders. Further, it hinders informed choice and results in an unbalanced attribution of responsibilities. While social and cultural values are protected, problems concerning privacy and liberty are likely to occur due to a stronger emphasis on the individual in contemporary Japan.