O'odham log

According to Nancy Butte, director of the Viva la Familia Project at Baylor College of Medicine in Houston, 40 to 60 percent of the prevalence of childhood obesity in the Hispanic population can be attributed to genetic factors. "Much has been written about children who are overweight," said Butte, explaining her study, "but little is known about why Hispanic children in particular tend to be more at risk for obesity." Many believe that there is, most likely, a set of genes that makes some people more susceptible than others. Butte suggests that at least part of the genetic component may be related to "the thrifty-gene hypothesis," the theory that some combinations of chromosomes create a situation in which cells are more inclined to store calories efficiently for times of scarcity. Some researchers have speculated that because many Mexican-Americans are descendants of American Indian hunter-gatherers, who evolved to store fat more easily for times of famine, those living a sedentary life in modern westernized societies with access to fast food may be more prone to gain weight.
... Throughout America, high-calorie fast food is cheaper than food that's good for you.
(http://www.nytimes.com/2005/01/02/magazine/02OBESITY.html?pagewanted=2)