The dual burden of obesity and undernutrition is a significant public health challenge worldwide, especially in the context of a changing climate. This essay presents the most recent nutritional evidence for the optimal diet for long-term health, and offers some commentary on how production of these foods affects the environment. Current dietary research supports a diet rich in fruits and vegetables; nuts, legumes, fish, and some poultry as protein sources; unsaturated fats replacing saturated fats; whole grains replacing refined grain products; dairy foods in low to modest amounts; and minimal amounts of red meat and added sugar. This healthy dietary pattern also supports sustainable agriculture and environmental preservation.