The continuous aging of the EU population challenges the sustainability of welfare states. Part of the solution is to ensure that people not only live longer but also better (i.e., that they can function independently while remaining free of disease/disability), which may be achieved through better nutrition and adoption of healthier lifestyles. We test that proposition with a behavioural model of diet quality choice and health determination. The simultaneous equations model, which accounts for the endogeneity of lifestyle choices and is applied to a sample of older Italians, allows for bi-directional causality between diet and health. The health production function confirms that good quality diets and other healthy lifestyles (e.g., physical activity, smoking and drinking) improve self-assessed health. In turn, the elderly respond to illness by improving their diets and exercising more. Supporting healthy aging may be achieved through targeted policies aimed at promoting healthy eating and other healthy lifestyles.