Drewnowski et al. Respond

Food prices are indeed a mechanism that links obesity and poverty.¹ As incomes decrease, energy-dense grains, sweets, and fats become the best way to provide daily calories at a manageable cost.² Added sugars and fats can be inexpensive, flavorful, satisfying, readily accessible, and convenient,³ but these ingredients can also provide minimal nutritional value. One factor behind rising obesity rates may be lower diet cost.⁴

In the United States, the most obese neighborhoods are those with low residential property values, few amenities, and high poverty rates.⁵ Richer and better educated people live in wealthier areas, shop at upscale supermarkets, enjoy high quality diets, and are more likely to be thin and healthy.⁶ Less food-secure people with lower incomes shop at lower-cost supermarkets, search for bargains, and may be driven by economic necessity to select lower-quality diets. Obesity in America is largely a socioeconomic issue.⁷

A rise in food prices caused by climate change will lead to higher, not lower, obesity rates in the United States. The spikes in food prices observed in 2008 and again in 2010 were highest for the healthier foods, particularly vegetables and fruit.⁸ The current drought conditions have damaged crops and will lead to food-price increases in 2013, especially for dairy, eggs, and meat. As food prices continue to increase, refined grains, added sugars, and vegetable fats will replace healthier options, first for the poor and later for the middle class.

Cereal and oilseed crops, not meat or dairy, account for most of the calories in the global food supply. Corn, wheat, rice, soy, and sugar cane are all staples that yield inexpensive dietary energy and provide fat, refined carbohydrates, and protein. Energy, land, and water resources for many other crops are becoming scarce, leading to justifiable concerns about hunger and food security worldwide.

We agree that the potential impact of climate change on global nutrition would benefit from a more detailed analysis.⁹ Fortifying global staples with vitamins and minerals to assure high nutrient density at a low cost is an approach adopted by the Gates Foundation and the Global Alliance for Improved Nutrition among others. Assuring genetic biodiversity by promoting traditional and local plants is a theme adopted by the Food and Agriculture Organization of the United Nations.¹⁰ A focus on nutrition, water, and rural development has characterized some food industry efforts. These and other options would benefit from sustained informed debate on global nutrition economics, obesity, and health.