Arizona’s Pima Indians exceed the type 2 diabetes rate (38 percent) of the genetically similar Pima Indians in Mexico (6.9 percent) by five times, according to a 2006 study by the American Diabetes Association.

While Arizona’s Pima Indians currently have the highest rates of diabetes and obesity in the United States, that wasn't always the case. They were lean until around 1890 when their water supply was overtaken by American settlers upstream. The United States government began subsidizing the tribe's food -- much of it containing sugar and white flour, and obesity and diabetes rates soared, said Dr. Guoxun Chen, assistant professor at The University of Tennessee Obesity Research Center.

The contingent of Pima who relocated to the Sierra Madre mountains of Mexico continued traditional farming, and the vast majority of Mexico's Pima Indians have maintained healthy weights, according to Dr. Eric Ravussin, a visiting scientist at the Phoenix Epidemiology and Clinical Research Branch at National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), who has studied obesity in the Pima Indians since 1984, states an NIDDK report.

Ravussin also points out the Pima predisposition to store fat efficiently due to survival mechanisms evolved in the harsh southwestern desert.

"There's no question these people suffer from a genetic disease," says Ravussin. "It's not sloth and gluttony."

Regardless, the drastically different diabetes and obesity rates of Mexico's Pima Indians versus Arizona's Pima Indians proves the significance of a healthy diet, including eating fresh vegetables and fruits and limiting consumption of manufactured food.

"We've learned from this study of the Mexican Pimas that if the Pima Indians of Arizona could return to some of their traditions, including a high degree of physical activity and a diet with less fat and more starch, we might be able to reduce the rate, and surely the severity, of unhealthy weight in most of the population," Ravussin said.