Researchers Pinpoint Array of Obesity Genes10/11/10
SUNDAY, Oct. 10 (HealthDay News) -- Scientists have found genes
that appear to play a role in the propensity for obesity.
The findings are reported in two new studies published in the
Oct. 10 online edition of
In one report, researchers say they have identified 18 gene
variants linked to obesity and confirmed the involvement of 14
others. In a second report, the same group of researchers say they
have identified 13 gene variants that appear to direct fat to the
belly or thighs.
"We have made a big leap forward in identifying new gene variations that contribute to the susceptibility to obesity and susceptibility to store fat more on your hips or more on your waist," said researcher Ruth Loos, a group leader in the Genetic Aetiology of Obesity Program in the MRC Epidemiology Unit at the Institute of Metabolic Science, in Cambridge, U.K.
Loos cautioned that these genes cannot be used to predict
whether an individual will become obese or not. Right now, they
have identified genes linked to obesity, but exactly how these
genes work in developing a vulnerability to obesity isn't known,
"But if we know the biology, perhaps we can invent a more effective preventive strategy. Maybe we can identify proteins that we can target with drugs," Loos said. "It's going to take years before these new discoveries will develop into new interventions."
In addition, having these gene variants doesn't mean that an
individual is definitely going to be obese. "The prediction is not
much better than just flipping a coin," Loos said.
For the first study, Loos and her colleagues looked at data from
46 gene studies that had identified genes linked to body mass index
(or BMI, a measurement that takes into account height and weight).
Together, these studies included 123,865 people.
In this meta-analysis, which is a review of previously published
studies, Loos' group was able to find 18 new genomic regions
associated with BMI, and confirm 14 regions that had been
Loos noted that the more of the gene variants a person has, the
greater their susceptibility to obesity. These variants are
inherited from both your mother and your father, so you can have as
many as 64 variants, she explained.
The average person has about 28 to 32 of these variants; about 2
percent of the population carries more than 38 variants and 2
percent of the population carries less than 21, Loos added.
These genes appear to act in the brain, Loos said. "This
suggests that these genes may act through increased food intake --
maybe appetite and reward," she said. "But you still need the
environment on top of that to really trigger that
Over the past 30 years, the obesity epidemic has exploded, Loos
pointed out. "Our genes haven't changed, our environment has
changed," she stated.
However, Loos added, there are several genes whose variants are
linked to extreme obesity.
In a second meta-analysis, Loos and colleagues looked at 32
genome-wide studies for genes associated with hip-to-waist ratio,
which is a measure of fat distribution. These studies included
The researchers identified 13 genes associated with hip-to-waist
ratio that had not been identified before. Among these genes, seven
had a stronger effect on women than men.
These findings show that there are sex-specific genes that
regulate fat distribution. Moreover, these genes and the ones in
the first study don't overlap, suggesting that different genes
regulate BMI and fat distribution.
The differences between where men and women store fat -- men on
the waist, women on the thighs -- is likely genetically driven,
Obesity expert Dr. David L. Katz, director of the Prevention
Research Center at Yale University School of Medicine, said "that
there are genes associated with variations in human shape and size
is no more surprising than genes associated with variations in eye
color, hair color or skin pigment."
Although finding genes associated with obesity is important for
understanding the biology of obesity, these new findings have
limited application in the current obesity epidemic, Katz said.
"Let us by all means study our genes, and their associations with our various shapes and sizes," he said. "But let's not let it distract us from the fact that our genes have not changed to account for the modern advent of epidemic obesity -- our environments and lifestyles have."
For more information on obesity, visit the
U.S. National Library of Medicine.
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