A healthy home environment could help offset children’s genetic
susceptibilities to obesity, according to new research led by
UCL.
The study, published this week in
JAMA Pediatrics,
found that the impact of genetic factors on weight is roughly
halved if a child is bought up in a less ‘obesogenic’ home
environment where healthy eating and exercise is more prevalent.
Researchers collected data on Body Mass Index (BMI) and home
environments from 925 twin pairs in the British Gemini cohort.
The twins’ families were asked in detail about many aspects of
their home diet, physical activity, and media environments,
such as the amount of healthy food in the home, how about how
many media devices there were in the home and family media
viewing habits.
This information was used to create a score for each home that
indicated if it was a ‘high-risk’ or ‘low-risk’ environment for
obesity. Of the 925 twin pairs, 508 were living in healthier,
‘low-risk’ home environments and 417 were living in less
healthy ‘high-risk’ home environments.
“Our study is the first to examine how the early home
environment relates to a child’s genetic susceptibility to
being overweight, even though it is widely believed to be a key
influence on weight,” said first author, Dr Stephanie Schrempft
(UCL Behavioural Science and Health).
“The finding that genetic influence on weight was stronger
among children living in riskier home environments supports a
theory, developed by our group, that genetic susceptibility to
obesity will be most highly expressed when individuals are
living in an obesogenic environment that encourages excess
consumption and low physical activity. In other words, 'the
genetic background loads the gun, but the environment pulls the
trigger'.”
The researchers used the twin design to estimate the genetic
and environmental influence on the BMI of children in both
high- and low-risk obesogenic home environments. A third of the
group consisted of identical twins who are 100% genetically the
same, and two-thirds of fraternal twins who are approximately
50% genetically the same. Comparing the two types of twins
allowed researchers to estimate genetic and environmental
influence on BMI.
If identical twins are much more similar than fraternal twins
for BMI, genes are important in shaping it. If the two types of
twins are fairly similar for BMI despite their genetic
differences, the home environment is an important factor.
Researchers found a much larger difference in similarity
between identical and fraternal twins when children were
bought-up in a high-risk home environment, indicating a greater
genetic influence on children’s BMI in an obesogenic
environment. In contrast, in a low-risk home environment, both
types of twins were much more similar, highlighting that a
healthy home environment can override genetic influence on BMI.
In the high-risk environment, genetic differences between
children explained 86% of differences in children’s BMI. In the
low-risk environment, genetic
differences between children were less important
in explaining differences in their BMI, accounting
for only 39% of BMI differences.
Dr Clare Llewellyn (UCL Behavioural Science and Health) senior
author, said: “We have known for decades that genes help to
explain why people differ in their weight, but this often leads
to the misconception that weight can’t be changed. This study
shows that genes are not destiny when it comes to weight. In
childhood, the home family environment seems to influence the
extent to which genetic predisposition to a lower or higher
weight is fully expressed.”
In particular, for children growing up in a healthy home food
environment, genetic influence on weight was fairly modest, and
the home environment was just as important. Ironically, this
study points more than anything to the importance of the early
environment for shaping a child’s weight.”
This work was supported by an Impact studentship to Dr
Schrempft and Cancer Research UK grant.
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