One disease that has a higher prevalence among Japanese Americans than their counterparts in either Japan or Whites in the U.S. is Type II Diabetes. In the Seattle studies, 20% of Nisei men between 45 and 74 were found to have diabetes, half of which were not diagnosed, and 56% had abnormal glucose tolerance. Those rates were over twice as high as comparable samples of men in the U.S. population in general (Fujimoto et al., 1987). Those with diabetes were found to consume more fat and animal protein than their non-diabetic Nisei counterparts, although both groups consumed the same amount of calories.

A study of Japanese Americans in King County, Washington reported that those with normal fasting blood sugars but impaired glucose tolerance or diabetic glucose tolerance had cardiovascular risk factors that were worse than those with normal glucose tolerance (Liao et al., 2001). It has been proposed that the Japanese may be genetically predisposed for a weaker insulin secretion response to a glucose load thus rendering them at increased risk for diabetes with a westernized diet low in fish and soy products (Nakanishi et al, 2004).