Strategies for environmental sustainability and global food security must account for dietary change. Using a biophysical simulation model we calculated human carrying capacity under ten diet scenarios. The scenarios included two reference diets based on actual consumption and eight "Healthy Diet" scenarios that complied with nutritional recommendations but varied in the level of meat content. We considered the U.S. agricultural land base and accounted for losses, processing conversions, livestock feed needs, suitability of land for crops or grazing, and land productivity. Annual per capita land requirements ranged from 0.13 to 1.08 ha person -1 year -1 across the ten diet scenarios. Carrying capacity varied from 402 to 807 million persons; 1.3 to 2.6 times the 2010 U.S. population. Carrying capacity was generally higher for scenarios with less meat and highest for the lacto-vegetarian diet. However, the carrying capacity of the vegan diet was lower than two of the healthy omnivore diet scenarios. Sensitivity analysis showed that carrying capacity estimates were highly influenced by starting assumptions about the proportion of cropland available for cultivated cropping. Population level dietary change can contribute substantially to meeting future food needs, though ongoing agricultural research and sustainable management practices are still needed to assure sufficient production levels.

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A principal effect of agricultural productivity growth is to accelerate urbanization by supplying food, labor and other resources to urban services and industry. Towns and cities may also grow for their own reasons, pulling food and resources out of rural areas. Whether pushed or pulled, the development of markets creates new opportunities for agricultural households. This study tests whether, on balance, proximity to older towns and cities has improved or worsened malnutrition among farm households in 43,850 survey clusters in 46 developing countries between 1986 and 2011, using 83 Demographic and Health Surveys (DHS) combined with other geographic and historical data. Controlling for national income, we find that regions with a longer history of urbanization have children with higher weight-for-height and heightfor-age z-scores at a wide range of national income levels. We also find a higher prevalence of overweight among mothers living near older cities. These results suggest that, on average, access to urban markets has reduced rural child stunting and wasting in the surveyed countries, but also increased the risks of overweight for children and adult women. These results motivate the need to guide agricultural market development in ways that promote improved nutrition while limiting the rise of diet-related disease.