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 bmis were in healthy weight ranges, though the biological living standards in rural areas exceeded those in urban areas. The increase in bmis during the twentieth century did not have its origin in the nineteenth century.