A new study found that the common belief that weight gain may result from the cessation of smoking may not always be the case. Researchers from the University of Glasgow discovered that heavy smokers are more at risk of having "pot belly" stomachs because smoking may push fats into the central areas of the body, leading to an apple-shaped, big-belly type of body.

The researchers conducted the study by performing a meta-analysis of 29 research studies with approximately 150,000 subjects, who have strict European ancestry and are aged 16 years and above. The studies include data about the participants' smoking habits, weight and the circumference of the waist. The researchers analyzed the genotypes, adiposity (fat) measures and statistical data related to the participants. All the studies included in the analysis were recipients of ethics approval from the local research ethics groups.

The findings of the study, published in the BMJ Open Journal, show that heavy smoking does result in lower body mass index (BMI) as per genetic variation data. However, while the general weight of frequent smokers was lower than that of nonsmokers, their waist circumference was higher, if BMI is included in the analysis.

"For a given BMI, a gene variant associated with increased cigarette consumption was associated with increased waist circumference. Smoking in an effort to control weight may lead to accumulation of central adiposity," researchers noted.

Study participants who possessed a genetic variant that suggests their extra cigarette consumption per day will lead to a lower BMI also have a 0.14 percent increase in waist circumference for every copy of the said gene, provided that their BMI stays the same. With this, the authors of the study suggest that there may be a preferential redistribution of fat toward the abdomen.

"On the whole, weight goes down in smokers," says Professor Naveed Sattar, study co-author from the Institute of Cardiovascular and Medical Sciences. This may mean that smoking may result in the decreasing possibility of fats settling in the "safe bits," he adds.

When a smoker gains weight, their tummies will exhibit bigger increases compared with the nonsmokers who gained the same amount of weight – something that may elevate the risk of diabetes. The potential development of an "apple-shaped" body, should the results of the study further be confirmed, may ignite a novel idea to boost smoking cessation.

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