Heavy smoking may lead to increased waist circumference

Heavy smoking may result in a relative increase
in waist circumference, according to a new study led by the University of
Bristol.

Professor Richard Morris of Bristol’s School of Social and Community Medicine
and colleagues compared people with a particular gene, which causes smokers to
smoke more heavily, to people without the gene.

On average, people with this gene were found to have a lower body mass index.
This was unsurprising and is in line with the generally accepted idea
that smoking can keep your weight down.

However, the researchers also noticed that for the same body mass index, people
with this gene had a greater waist circumference. This suggests that even
if you keep your weight down overall by smoking, you may end up with fat being
deposited around the stomach, a condition known as ‘central adiposity’.
Not only would this suggest that adults who smoke either may gradually
acquire an ‘apple shape’ or ‘paunch’, but such adults might then increase their
risk of developing type 2 diabetes.

Professor Morris said: “When doctors attempt to persuade their patients to stop
smoking, one barrier those patients face is a fear of weight gain. In the
short term, the average smoker is right to be concerned about this.
However, continuing to smoke may not necessarily result in weight control
in the right parts of the body, and if so may in fact increase the risk of
diabetes.”

The findings were based on 29 studies across the world involving 150,000 people
who either smoked, used to smoke or have never smoked.

If these findings are confirmed in future research, a tendency for smokers to
acquire an ‘apple shape’ due to increasing central adiposity might provide a
novel health promotion message to encourage smokers to quit smoking, the
researchers said.

The paper is published in BMJ Open.

Paper

‘Heavier smoking may lead to a relative increase in waist circumference: evidence for a causal relationship from a Mendelian randomisation meta-analysis. The CARTA consortium’ by Morris et al in BMJ Open [Open Access]