Obesity and diabetes study weighs
influence of genetics, lifestyle
A team of Northern Arizona University-led researchers is using nearly
$1.3 million in new funding from the National Institutes of Health to continue with the world’s longest-running study on obesity and Type 2 diabetes.
Obesity and diabetes have been described as the major public health concerns of the 21st century, explains Leslie Schulz, executive dean of NAU’s College of Health and Human Services and the study's principal investigator. “This study is taking those necessary steps toward finding a way to protect people against the development of these pervasive diseases,” she says.
Schulz is being joined by researchers from the National Institutes of Health, the Pennington Biomedical Research Center and Mexico’s Center for the Investigation of Nutrition and Development.
A related study already has shown that Pima Indians in Arizona—who have a diet and lifestyle similar to most Americans—have a much higher rate of diabetes than the national average: 38 percent versus 8 percent nationally, giving them the distinction of being the most diabetes-prone group in the world.
The Arizona Pima Indians have been genetically linked to a village of Pima Indians living a more traditional lifestyle in a remote, mountainous region of Mexico. A 1995 study of the Mexican Pimas revealed only a rare occurrence of diabetes. Schulz explains that the genetic similarities between the two groups of Pima Indians, along with the contrast in their lifestyles, provides an ideal setting to study the relationship between environmental circumstances and diabetes.
The researchers will return this fall after 15 years to the Mexican village to study the relationship between the Mexican Pima Indians’ increasingly “westernized” lifestyle and their genetic predisposition for obesity and diabetes.
“Since we were last there, the environmental circumstances of the village have changed,” Schulz says, explaining how the electrical supply to the region has increased, cars have become more prevalent and grocery stores have appeared.
She points out that this changing environment affects non-Pima Mexicans who also live in the village as much as it does the Mexican Pima Indians living there.
“These two groups of people have undergone the same lifestyle changes over the past 15 years but they have different genes,” Schulz explains. “Therefore, we hope to separate out the role genes play versus the role lifestyle plays.”
Schulz says the team of researchers will spend weeks at a time over the next two years living and working in “rustic” conditions in the Mexican village. There they will collect and record data, such as residents’ height, weight, diet and physical activity, and determine whether or not the residents have diabetes.
“What is exciting is that we will be employing state-of-the-science methodology, the most cutting-edge techniques for looking at metabolic rate and the number of calories people burn, in a setting that is very challenging,” she says. Meanwhile, the extensive genetic aspects of the study will take place in the United States.
The researchers are attempting to answer why a person who is genetically predisposed to develop diabetes does not develop it.
“What is it about their environment or lifestyle that changes that?” asks Schulz. “This study is unique because we can actually measure the changes in lifestyle over the last 15 years.”
Schulz says that the researchers are expecting to find an increase in Type 2 diabetes and obesity among the Mexican Pimas that parallels the changes in their lifestyle. It’s a pattern that has been documented in other countries undergoing dramatic industrial and economic development, like China, where diabetes prevalence has increased threefold over a 10-year period. Similar findings have been recorded in India.
While this may seem like bad news for the developing world, Schulz said there is hope in the implication that diabetes can be prevented in populations with a predisposition for the condition.
The team of researchers intends to publish its findings from this phase of the study in 2012.
The original research project was featured on a segment of Scientific American Frontiers called “Feast or Famine" in 1994, on 60 Minutes in 2004 and most recently on a 20-minute segment on National Public Radio.