Causes of Morbid Obesity
* The Pima Paradox

The Pima Indians are known in scientific circles as one of the heaviest groups of people in the world. In fact, National Institutes of Health researchers have been studying them for more than 35 years. Some adults weigh more than 500 pounds, and many obese teenagers are suffering from diabetes, the disease most frequently associated with obesity.

But here's a really interesting fact - a group of Pima Indians living in Sierra Madre, Mexico, does not have a problem with obesity and its related diseases. Why not?

The leading theory states that after many generations of living in the desert, often confronting famine, the most successful Pima were those with genes that helped them store as much fat as possible during times when food was available. Now those fat-storing genes work against them.

Though both populations consume a similar number of calories each day, the Mexican Pima still live much like their ancestors did. They put in 23 hours of physical labor each week and eat a traditional diet that's very low in fat. The Arizona Pima live like most other modern Americans, eating a diet consisting of around 40 percent fat and engaging in physical activity for only two hours a week.

The Pima apparently have a genetic predisposition to gain weight. And the environment in which they live - the environment in which most of us live - makes it nearly impossible for the Arizona Pima to maintain a normal, healthy body weight.