IF YOU were born during a particularly cold winter, the chances are that you
will end up getting fatter as you get older, say researchers in Southampton and
Chicago.
Although lifestyle and genetics obviously play an important role in whether
you pile on the pounds, the influence of the environment on the fetus may also
be have an impact, according to David Phillips of the Medical Research Council
Environmental Epidemiology Unit at the University of Southampton and James Young
of the Northwestern University Medical School in Chicago. 鈥淲e鈥檝e forgotten that
environment in early life is important,鈥� says Phillips.
Phillips and his colleagues examined body mass index (BMI) data from 1750 men
and women who had been born in Hertfordshire between 1920 and 1930 and had lived
there all their lives. The BMI provides a measure of obesity. It is calculated
by taking a person鈥檚 weight in kilograms and dividing by the square of their
height in metres. Obese people have a larger BMI.
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The researchers then classified the winters between 1920 and 1930 as either
鈥渕ild鈥� or 鈥渃old鈥�, and found that there was a marked increase in BMI among men
born in cold winters. As the researchers will report in the International
Journal of Obesity, the effect was also apparent for the women, though less
pronounced.
鈥淲e don鈥檛 properly understand why it occurs,鈥� Phillips admits. He suggests
the effect could arise from the cold setting limits on how hormones behave,
possibly by influencing the thyroid gland. 鈥淎nimal experiments suggest it鈥檚
relative, not absolute temperature that causes the effect,鈥� he adds. 鈥淪o this
might explain why children of people who emigrate from hot to colder countries
are prone to get fat.鈥�