Researchers have identified six new gene mutations linked to obesity and said on Sunday they point to ways the brain and nervous system control eating and metabolism.

"Today's findings are a major step forward in understanding how the human body regulates weight," Dr. Alan Guttmacher, acting director of the National Human Genome Research Institute, said in a statement.

"This study essentially doubles in one fell swoop the number of known and replicated genetic factors contributing to obesity as a public health problem," added Dr. Kari Stefansson, Chief Executive Officer of deCODE Genetics of Iceland and one of the researchers.

The international team analyzed 300,000 one-letter mutations in the genetic code known as single nucleotide polymorohisms or SNPs in more than 30,000 people from Iceland, the Netherlands and the United States.

They cross-checked their findings in 40,000 people from Denmark and the United states.

They found variations in six genes -- TMEM18, KCTD15, GNPDA2, SH2B1, MTCH2 and NEGR1 -- were strongly associated with a height-to-weight ratio known as body mass index or BMI.

"Today's findings are a major step forward in understanding how the human body regulates weight," said Guttmacher, whose institute, one of the National Institutes of Health, helped fund and conduct the study.

"One of the most notable aspects of these discoveries is that most of these new risk factors are near genes that regulate processes in the brain," added Stefansson, whose company hopes to sell genetic tests based on such discoveries.

"This suggests that as we work to develop better means of combating obesity, including using these discoveries as the first step in developing new drugs, we need to focus on the regulation of appetite at least as much as on the metabolic factors of how the body uses and stores energy," Stefansson said.

"These new variants may point to valuable new drug targets," he added.

Nearly a third of US adults are considered obese with a BMI of 30 or more. Obesity is associated with more than 100,000 deaths each year in the US population and trends are similar in many other countries.

"We know that environmental factors, such as diet, play a role in obesity, but this research further provides evidence that genetic variation plays a significant role in an individual's predisposition to obesity," said the genome institute's Dr. Eric Green.

(China Daily via Agencies December 16, 2008)