Lifestyle plays a major role in most of the illnesses in industrialised nations.¹ Six of the 10 leading factors contributing to the global burden of disease are lifestyle related: unsafe sex, high blood pressure, tobacco use, alcohol use, high cholesterol and obesity.² Lifestyle-related illnesses also contribute to the rising costs of healthcare. Spending on healthcare accounts for about 16% of the gross domestic product in the USA, or US$1.9 trillion.³ Although smoking has declined steadily there since the 1960s, smoking-related medical expenses are still about US$75.5 billion per year.⁴ Obesity, which has been climbing in the past two decades, accounts for about US$75 billion in healthcare costs there each year.⁵ Alcoholism and drug addiction in the USA account for annual healthcare costs of about US$22.5 billion and US$12 billion, respectively.^6,7 Federal government spending on healthcare relating to HIV/AIDS is over US$13 billion per year.⁸

Given the well-documented relationship between lifestyle, disease burden and healthcare costs, it makes economic and medical sense to hold individuals morally responsible for their health-related choices. While this view has a great deal of intuitive appeal, it also faces numerous objections.^9–12 First, holding individuals entirely responsible for their own health conflicts with medicine’s obligation to treat the sick and society’s obligation …