Heavy smoking may lead to a fatter stomach, new research suggests.

While many smokers cite fear of weight gain as a reason for not giving up, scientists have found they are more likely to develop pot bellies than non-smokers.

Scientists at the University of Glasgow found that while smoking might be associated with lower overall weight, it tends to push fat into central areas resulting in a bigger stomach - an unhealthy apple shape, rather than a healthy pear shape.

In their study, the researchers analysed 29 studies involving almost 150,000 participants containing data on their smoking habits, weight and waist circumference.

The analysis revealed a genetic variation in some smokers which was associated with an increase in the number of cigarettes consumed and a lower mean body mass index (BMI), suggesting that heavier smoking leads to lower BMI.

However the data, published in the BMJ Open journal, also showed that while overall BMI in heavy smokers was lower, waist circumference was higher than non-smokers once BMI was accounted for.

Professor Naveed Sattar, of the Institute of Cardiovascular and Medical Sciences who co-led the study, said: "One barrier to smoking cessation is the fear of weight gain and whilst smoking lessens weight overall, it tends to push fat more into the central area so waist circumference is preferentially higher.

"So, when smokers put on weight, they will show bigger tummies for same weight gain than non-smokers and this may also be linked to their greater risk for diabetes.

"On the whole weight goes down in smokers. That's true at point of smoking, but it means smoking is lessening the chance of putting fat on in the 'safe bits'."