Sugar, rum, and tobacco are commodities which are nowhere necessaries of life, which are become objects of almost universal consumption, and which are therefore extremely proper subjects of taxation. — Adam Smith, The Wealth of Nations, 1776

The obesity epidemic has inspired calls for public health measures to prevent diet-related diseases. One controversial idea is now the subject of public debate: food taxes.

Forty states already have small taxes on sugared beverages and snack foods, but in the past year, Maine and New York have proposed large taxes on sugared beverages, and similar discussions have begun in other states. The size of the taxes, their potential for generating revenue and reducing consumption, and vigorous opposition by the beverage industry have resulted in substantial controversy. Because excess consumption of unhealthful foods underlies many leading causes of death, food taxes at local, state, and national levels are likely to remain part of political and public health discourse.

Sugar-sweetened beverages (soda sweetened with sugar, corn syrup, or other caloric sweeteners and other carbonated and uncarbonated drinks, such as sports and energy drinks) may be the single largest driver of the obesity epidemic. A recent meta-analysis found that the intake of sugared beverages is associated with increased body weight, poor nutrition, and displacement of more healthful beverages; increasing consumption increases risk for obesity and diabetes; the strongest effects are seen in studies with the best methods (e.g., longitudinal and interventional vs. correlational studies); and interventional studies show that reduced intake of soft drinks improves health.1 Studies that do not support a relationship between consumption of sugared beverages and health outcomes tend to be conducted by authors supported by the beverage industry.2

Daily Caloric Intake from Sugar-Sweetened Drinks in the United States. Data are from Nielsen and Popkin.3

Sugared beverages are marketed extensively to children and adolescents, and in the mid-1990s, children's intake of sugared beverages surpassed that of milk. In the past decade, per capita intake of calories from sugar-sweetened beverages has increased by nearly 30% (see bar graph)3; beverages now account for 10 to 15% of the calories consumed by children and adolescents. For each extra can or glass of sugared beverage consumed per day, the likelihood of a child's becoming obese increases by 60%.4

Taxes on tobacco products have been highly effective in reducing consumption, and data indicate that higher prices also reduce soda consumption. A review conducted by Yale University's Rudd Center for Food Policy and Obesity suggested that for every 10% increase in price, consumption decreases by 7.8%. An industry trade publication reported even larger reductions: as prices of carbonated soft drinks increased by 6.8%, sales dropped by 7.8%, and as Coca-Cola prices increased by 12%, sales dropped by 14.6%.5 Such studies — and the economic principles that support their findings — suggest that a tax on sugared beverages would encourage consumers to switch to more healthful beverages, which would lead to reduced caloric intake and less weight gain.

Relative Price Changes for Fresh Fruits and Vegetables, Sugars and Sweets, and Carbonated Drinks, 1978–2009. Data are from the Bureau of Labor Statistics and represent the U.S. city averages for all urban consumers in January of each year.

The increasing affordability of soda — and the decreasing affordability of fresh fruits and vegetables (see line graph) — probably contributes to the rise in obesity in the United States. In 2008, a group of child and health care advocates in New York proposed a one-penny-per-ounce excise tax on sugared beverages, which would be expected to reduce consumption by 13% — about two servings per week per person. Even if one quarter of the calories consumed from sugared beverages are replaced by other food, the decrease in consumption would lead to an estimated reduction of 8000 calories per person per year — slightly more than 2 lb each year for the average person. Such a reduction in calorie consumption would be expected to substantially reduce the risk of obesity and diabetes and may also reduce the risk of heart disease and other conditions.

Some argue that government should not interfere in the market and that products and prices will change as consumers demand more healthful food, but several considerations support government action. The first is externality — costs to parties not directly involved in a transaction. The contribution of unhealthful diets to health care costs is already high and is increasing — an estimated $79 billion is spent annually for overweight and obesity alone — and approximately half of these costs are paid by Medicare and Medicaid, at taxpayers' expense. Diet-related diseases also cost society in terms of decreased work productivity, increased absenteeism, poorer school performance, and reduced fitness on the part of military recruits, among other negative effects.

The second consideration is information asymmetry between the parties to a transaction. In the case of sug