MRC Institute of Genetics & Molecular Medicine
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Study reveals effects on body mass index of gene linked to heavy smoking

Collaboration between the University of Bristol and IGMM researchers: December 2014

A genetic variant which causes smokers to smoke more heavily has been shown to be associated with increased body mass index (BMI) – but only in those who have never smoked, according to new research. It is likely that this finding has not come to light before because it has been masked by the effect of smoking, which acts to reduce BMI.

Researchers at University of Bristol, working with collaborators including IGMM researchers Archie Campbell, Riccardo Marioni and Caroline Hayward, studied a variant in the CHRNA5-A3-B4 gene cluster which is known to increase smoking heaviness.

They found that the variant is associated with lower BMI in current smokers, but higher in people who have never smoked.  This difference in effects suggests that the variant influences BMI in opposite directions – via  pathways other than smoking for those who have never smoked and by increasing the weight-reducing effects of smoking in those who smoke.