The food system accounts for a large share of fossil fuel consumption in the United States, and energy accounts for a substantial and highly variable share of food costs. This intersection between food and energy markets suggests that public and private decisions affecting one market will have spillover effects in the other. For example, would increasing the share of population having diets that align with Federal dietary guidance reduce fossil fuel use in the U.S. food system? Would a carbon dioxide (CO 2 ) tax improve diet quality? To address these issues, we use the most recent data available to integrate the material-flows accounting framework adopted by the United Nations Statistical Commission into the existing food-system accounting structure of the ERS Food Dollar accounts. Then, we use mathematical optimization to model healthy diets. Our research indicates that U.S. agri-food industries are more sensitive to energy price changes than nonfood industries. We find that in 2007, fossil fuels linked to U.S. food consumption produced 13.6 percent of all fossil fuel CO 2 emissions economywide. Our study of alternative diets shows there are many ways to meet the Dietary Guidelines for Americans. If Americans made a minimal dietary shift to eat healthy, we find food-system energy use would decrease by 3 percent. By making greater changes from current consumption, we find food- system energy use could be reduced by as much as 74 percent. A tax on CO 2 emissions from fossil fuels would increase the cost of a typical meal by an average of 1.7 percent, with estimates ranging between 0.2 and 5.4 percent. ----- Errata: On March 8, 2017, ERS corrected a few errors made in the calculation of data reported in Figure 14 (p. 32) and in the calories columns in Table 5 (p. 34). References to these data were updated in the text on pages 31- 33 and p. 42. Also, a superscript on q on p. 89 was changed from a 1 to 0.