Body mass index (BMI ) values reflect the net balance between nutrition, work effort, and calories consumed to fight disease. Nineteenth-century prison records in the United States demonstrate that the BMI values of blacks and whites were distributed symmetrically; neither underweight nor obese individuals were common among the working class. BMI values declined throughout the nineteenth century. By modern standards, however, nineteenth-century BMI s were in healthy weight ranges, though the biological living standards in rural areas exceeded those in urban areas. The increase in BMI s during the twentieth century did not have its origin in the nineteenth century.