Issue date: 4/4/07 Section: News

Scientists have discovered a certain "thrifty genotype," which affects how fat is stored and metabolized, according to a recent article in Newsweek.

In individuals with this gene, fat is stored in larger amounts, and it is burned at slower rates. This genetic variation gave certain individuals a competitive advantage in survival, protecting them in the Ice Age.

Don Cipollini, Ph.D, associate professor in the department of biological sciences, said evolution is the process of a change of genotype frequencies through time. This change can arise through a variety of mechanisms, such as natural selection.

Individuals that carry a specific genotype will be favorably selected for survival in a particular environment.

These traits increased the likelihood for survival, and individuals were able to pass on these genes in reproduction. Over time, certain genetic traits become more frequent and unique to certain populations.

It sometimes takes thousands of generations to see substantial changes, said Cipollini.

In the Ice Age, 30,000 years ago, individuals that carried this gene for a slower fat metabolism were better equipped to handle the extreme climate, and therefore more likely to survive and to pass on their genes to future generations, thus increasing the frequency of the "thrifty gene."

"We have been able to circumvent natural selection with a modern diet and modern medicine," Cipollini said. Genetic codes are being passed from one generation to anther without regard to environmental pressures.

The ability to store fat and to metabolize it sparingly was useful in a time of scarce food resources. However in a culture of abundant, cheap, high calorie food, the legacy of evolution has made us more vulnerable to weight gain.

People of Asian descent are particularly susceptible to weight gain and this gene. The number of Chinese considered obese has doubled between 1992 and 2002. Scientists, according to the Newsweek article, studied North American tribes, descendants of the people who crossed the land bridge over the Bering Strait from Asia.

This has also affected other sub-Asian groups, such as Eskimos and Pacific islanders. Populations of the Mediterranean and Africa may not have acquired this gene.

This new research could be used for genetic screening. If individuals find they have a propensity to store fat in this way, they should begin to make certain nutritional choices as a child.
While it helped their ancestors to survive the Ice Age, this "thrifty gene" has made people more vulnerable to the fast food lifestyle of the modern age.

When the average person eats food high in saturated fats, his or her "good" cholesterol goes down, and the "bad cholesterol" goes up. A person with the "thrifty genotype" is more sensitive to these types of foods, and will see more intense responses such as higher "bad cholesterol" levels.

The environment of the Ice Age favored people who were able to store fat and use it slowly. However, the result has produced a generation of people who are more likely to develop diseases such as heart disease in the copious supply of high-caloric foods.

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