Efforts to counter the rise in overweight and obesity, such as taxes on certain foods and beverages, limits to commercial advertising, a ban on chocolate drink at schools or compulsory physical exercise for obese employees, sometimes raise questions about what is considered ethically acceptable. There are obvious ethical incentives to these initiatives, such as improving individual and public health, enabling informed choice and diminishing societal costs. Whereas we consider these positive arguments to put considerable effort in the prevention of overweight indisputable, we focus on potential ethical objections against such an effort. Our intention is to structure the ethical issues that may occur in programmes to prevent overweight and/or obesity in order to encourage further debate. We selected 60 recently reported interventions or policy proposals targeting overweight or obesity and systematically evaluated their ethically relevant aspects. Our evaluation was completed by discussing them in two expert meetings. We found that currently proposed interventions or policies to prevent overweight or obesity may (next to the benefits they strive for) include the following potentially problematic aspects: effects on physical health are uncertain or unfavourable; there are negative psychosocial consequences including uncertainty, fears and concerns, blaming and stigmatization and unjust discrimination; inequalities are aggravated; inadequate information is distributed; the social and cultural value of eating is disregarded; people's privacy is disrespected; the complexity of responsibilities regarding overweight is disregarded; and interventions infringe upon personal freedom regarding lifestyle choices and raising children, regarding freedom of private enterprise or regarding policy choices by schools and other organizations. The obvious ethical incentives to combat the overweight epidemic do not necessarily override the potential ethical constraints, and further debate is needed. An ethical framework to support decision makers in balancing potential ethical problems against the need to do something would be helpful. Developing programmes that are sound from an ethical point of view is not only valuable from a moral perspective, but may also contribute to preventing overweight and obesity, as societal objections to a programme may hamper its effectiveness.