People who use MSG to add flavor to food are more likely to be overweight than people who eat the same amount and exercise just as much, according to a study from the University of North Carolina at Chapel Hill.

Researchers studied 750 men and women in rural China. Most did not use any commercially prepared foods, and 82 percent put MSG in, researchers said.

The one-third who used the most MSG were three times more likely to be overweight than those who didn't use it.

MSG, formally known as monosodium glutamate, is used to enhance flavor in many processed foods.

As the percentage of overweight and obese people around the world continues to increase, finding clues to the cause could be very important, Dr. Ka He said.

"The U.S. Food and Drug Administration and other health organizations around the world have concluded that MSG is safe," He said, "but the question remains -- is it healthy?"

The work was published in the journal Obesity.