Body Mass More Nurture Than Nature, Study
November 6, 2013
A DNA study in more than 20,000 pairs of siblings has found that the influence of genes on BMI scores is lower than previously thought.
Asian Scientist (Nov. 6, 2013) - The influence of genes on body mass index scores is substantially lower than previously thought, researchers at the University of Queensland have found.
The research, published in the American Journal of Human Genetics, provides new insights into the genetic influences underlying a person’s body mass index (BMI), which is calculated based on a person’s body weight and height.
Lead researcher Dr Gibran Hemani says that researchers have long debated how much of an influence a person’s genes have on his/her BMI.
“Some studies claim that more than 80 percent of BMI is due to genetic factors with less than 20 percent being driven by environmental factors, whereas others have put the figure much lower,” said Dr Hemani. “We wanted to come at the question from a different angle, using very large and complex sets of data and a method that is more reliable than previous studies.”
Human DNA varies at millions of positions across the genome. How, and how much, these genetic variations lead to differences in BMI is gradually becoming understood.
The researchers obtained DNA data on 20,240 pairs of siblings for their research because of their characteristic of being genetic similar. On average, if an individual has a variant at a particular position in the genome then his or her sibling will have a 50 percent chance of sharing that same variant. By counting the total number of DNA variants shared across the whole genome, the team could identify how genetically similar (or dissimilar) each pair of siblings was.
They found that although on average siblings were 50 percent genetically identical, the exact figure varied from about 35 percent to 65 percent, meaning that some sibling pairs are more genetically similar than others. Using this method, Dr Hemani and his colleagues calculated whether siblings who were more genetically similar were on average more similar in terms of BMI, and found that 42 percent of BMI is under the influence of genetics.
Dr Hemani said the study also has contributed in other ways in trying to understand how genetics influence BMI.
“We know that there are a huge number of variants across the genome, but how many of them actually have a direct influence on a complex trait like BMI? This is an important question because many researchers who study disease are focused on one particular genetic change or a gene of interest as the cause of the disease; however, there is growing evidence, including from this study, that disease is caused by thousands of small changes and it’s the additive effect of these changes that results in disorder.”
Source: University of Queensland; Photo: Natashi Jay/Flickr/CC.
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