High rate of obesity in United States is attributed to fast food culture. Recent research revealed that many fast-food meals begin with a single ingredient: corn. Research team led by A. Hope Jahren, a geo-biologist and professor at the University of Hawaii reached this conclusion after analyzing 480 fast food products at three restaurants from each of the three major chains in Los Angeles, San Francisco, Detroit, Denver, Boston and Baltimore.

Researchers tried to determine the animals' diet and in what conditions they were raised by using a technique that identifies carbon and nitrogen isotopes in meat.

Analysis of the fast food with new technique showed that high levels of carbon and nitrogen, which further revealed that the cattle and poultry were predominantly fed corn, which makes them very fat in a very short period of time.

After analyzing fries at the three restaurants, the researchers found that Wendy's used only corn oil, while McDonald's and Burger King used other vegetables oils.

A. Hope Jahren said: "We found that corn is not just a grain used in the production of fast food, it is the basis of all fast food. Of the hundreds of fast-food meals we purchased across the country, there were only about 12 servings of food that could potentially be traced back to something besides corn."