Vigorous physical activity could blunt the effects of a common
gene linked to obesity, claim US researchers.
Carrying two copies of the FTO gene significantly increases
the chances of becoming obese.
However, a study carried out among the US Amish community
found an active lifestyle appeared to remove this risk.
A UK specialist said the results, reported in the Archives
of Internal Medicine journal, would be interesting if repeated
by larger studies.
The complex relationships between our genes and lifestyles,
which can mean obesity for some people and not for others,
has yet to be fully understood.
Several genetic variants have been linked to obesity, but
none is wholly responsible for it.
The most common of these is FTO, with half of all people
in Europe carrying either one or two copies of it.
It is not clear how it influences weight gain, although some
scientists have suggested it may play a role in an individual's
The study from the University of Maryland supports other
research which suggests that a person's level of exercise
may help determine whether their genetic makeup will contribute
The researchers looked at 704 Amish men and women, chosen
because of that community's relative genetic "purity", with
members generally able to trace their ancestry back for 14
generations to early settlers from Europe.
Volunteers were fitted with "accelerometers", measuring their
precise movements over a period of time.
They found that while the expected link between the number
of copies of FTO carried and increased body mass index could
be seen in less active volunteers, that link was broken once
in those who recorded high levels of activity - equivalent
to three to four hours of moderately intensive activity.
Dr Soren Snitker, who led the research, said: "Our results
strongly suggest that the increased risk of obesity due to
genetic susceptibility can be blunted through physical activity.
"Some of the genes shown to cause obesity in our modern environment
may not have had this effect a few centuries ago when most
people's lives were similar to that of present-day Amish farmers."
Professor Andrew Hattersley, from Peninsula Medical School
in Devon, who also carries out research into the FTO gene,
said that this was the second study which suggested that exercise
levels could have a bearing on the way this gene had an effect
"Because the gene effects are very small, it would be good
to see this repeated in larger studies.
"The weight of evidence for physical activity potentially
overcoming genetic susceptibility is increasing."