Overeating disrupts entire networks of genes in the body, causing not only obesity, but diabetes and heart disease, in ways that may be possible to predict, researchers reported on Sunday.

The researchers developed a new method of analyzing DNA and used it to discover that obesity is not only complex -- something already known -- but complex in ways that had not been previously understood.

"Obesity is not a disease that is the result of a single change to a single gene. It changes entire networks," said Eric Schadt, executive director of Genetics at Merck Research Laboratories.

His team identified networks of hundreds of genes that appear to be thrown out of kilter when mice are fed a high-fat diet.

"This network is completely rocked by exposure to a high-fat, Western-type diet," Schadt said.

They then turned to a database of Icelandic people being studied by Decode Genetics Inc and found people have the same networks.

The joint teams did a detailed study of 1,000 blood samples and almost 700 samples of fat tissues from some of the Icelandic volunteers.

A chemical used to give butter flavor to popcorn can damage the lungs and airways of mice, U.S. government experts reported on Thursday.

Tests on mice show that diacetyl, a component of artificial butter flavoring, can cause a condition known as lymphocytic bronchiolitis, said the team at the National Institute of Environmental Health Sciences, part of the National Institutes of Health.

The condition can lead to obliterative bronchiolitis -- or "popcorn lung" -- a rare and debilitating disease seen in workers at microwave popcorn packaging plants and at least one consumer.

At least two microwave popcorn makers -- ConAgra Foods Inc and Weaver Popcorn Co Inc -- have said recently they would stop using diacetyl.

Laboratory mice made to inhale diacetyl vapors for three months developed lymphocytic bronchiolitis, the NIEHS team said.

"This is one of the first studies to evaluate the respiratory toxicity of diacetyl at levels relevant to human health," Daniel Morgan at NIEHS, whose team led the study, said in a statement.