This article describes the integration of life-cycle assessment methods with a new input-output model of the world economy to analyze the environmental and economic implications of alternative future diets. The article reviews findings by industrial ecologists about the energy and land required for the production and consumption of alternative foods and diets in several European countries. It also reviews attributes of foods and diets identified by nutritionists as reducing the risks of obesity and major chronic diseases related to the diets of the affluent. The predominantly plant-based Mediterranean-type diet emerges as a dietary scenario that could satisfy both sets of concerns. The likely implications for agriculture and for farm policies of a shift toward this diet from the current average diet in the United States are discussed and shown to be substantial. The one-country studies reviewed in the article provide substantial insights into the potential ramifications of dietary change. Many of the limitations of these studies could be overcome by conducting the analysis in a global framework that represented the relationships among consumption, production, and trade and the physical constraints within which they operate. Analysis of the environmental and economic implications of alternative scenarios describing healthy diets can help stimulate more intensive dialogue, debate, and action among the interested parties; such analysis can both benefit from and contribute to initiatives such as the World Health Organization's global strategy on diet and health, which intends to enlist the support of governments, corporations, and civil society.