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 “This is an exciting time in science especially with respect to
understanding the genetic basis of disease. There has been an
explosion in our knowledge of the genes involved in susceptibility
to obesity,” lead author Yann Klimentidis of the University of
Arizona in Tucson told Reuters Health by phone.
For example, he said, genes “could modulate how hungry we get or how
quickly we become full after eating, modulate how active we are, and
some people can sit for hours on end without any problem, some
cannot sit for more than a few minutes.”
“Those things probably have some genetic underlying factors,” he
said.
Klimentidis and colleagues used two large, long-term studies
involving more than 4,000 subjects each, known as the Framingham
Heart Study and the Women’s Health Initiative, to examine whether a
common variant of a gene called FTO was related to self-reported
time spent sitting.
Klimentidis said that of all genes researched so far, FTO gene has
the biggest effect on body mass index (BMI), which is a ratio of
weight to height.
In the Framingham Heart Study, the BMI-increasing FTO variant was
more common among people who also reported spending more time
sitting. The link between time spent sitting and BMI was strongest
for people with more high-risk FTO gene variants, which suggests
that “sedentary time” may have more affect on body mass for those
who have those genes.
There was also a significant interaction in the Women’s Health
Initiative, but it seemed to go in the opposite direction, the
authors report in the International Journal of Obesity.
Though we may model our level of activity on that of our parents
because that’s what we see growing up, we also inherit some
predisposition to sitting – or not sitting – in our genes,
Klimentidis said.
“Even deep among scientists, people underestimate the extent to
which behavior is genetically controlled,” he said.
“We still don’t know how FTO increases BMI,” Klimentidis said.
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Understanding how newly identified genes interact with lifestyle
factors will someday help take a genetic profile and determine which
interventions will be most effective to maintain a healthy weight,
he said.
“Maybe physical activity will really benefit me a lot, but for
someone else with a different set of genes physical activity might
not help them as much, they might have to do twice as much as me,”
Klimentidis said.
“As we learn about how the specific genes affect obesity we might
learn more about biological mechanisms, and we can target those
biological mechanisms through drugs,” or through specific preventive
measures, he said.
But so far, it is too soon to map everyone’s genes looking for the
high-BMI variant of the FTO gene, which is found in more than a
quarter of people with European descent, he said.
“What we’ve learned is there are not a handful of genes that
determine obesity, but hundreds of thousands of genes, each with
very small effects,” he said. “One gene tells a tiny part of the
story.”
SOURCE: http://bit.ly/1jE6Euk International Journal of Obesity,
online October 22, 2015.
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