Smoking has been linked to the accumulation of dangerous visceral fat

Fear of getting fat is a common excuse for smokers to avoid quitting the bad habit. But a new study has found that smoking may contribute to the accumulation of abdominal fat, including particularly dangerous visceral fat.

Smokers tend to weigh less than nonsmokers, but they also have more fat in their abdomen, including between abdominal organs. This is internal, or so-called visceral fat, which is considered by medical professionals to be the most dangerous type of adipose tissue. Being deep inside, it produces toxins that cause chronic inflammation, elevated sugar levels and damage to blood vessels. As a result, it leads to the development of heart disease, diabetes, stroke and dementia.

In a fresh paper that was published by the journal Addiction, experts at the research center at the University of Copenhagen, Denmark, confirmed that smoking can cause an increase in such "unhealthy" fat.

To assess the causal relationship, scientists used a method of statistical analysis called "Mendelian randomization" (Mendelian randomization, MR). With its help, the authors analyzed summary statistics from a number of past European Genome-wide association studies (GWAS) containing data on people's smoking habits and body fat distribution. One included a sample of more than 1.2 million people, and the other had more than 600,000 participants.

Relying on genetic databases, the Danish scientists first identified genes associated with smoking habits and body fat distribution. They then tracked whether those with genes correlating with smoking were prone to fat loss. To make sure that the identified link between the bad habit and body fat distribution was due to smoking, the researchers also made adjustments for other factors, including alcohol consumption and socioeconomic status.

In the end, it was found that starting smoking and maintaining the habit throughout life can lead to increased fat accumulation on the abdomen, as indicated by the ratio of waist to hip size. The analysis also showed that it was more often visceral, rather than subcutaneous, fat.

"Previous studies have been subject to distortions, which happens under the influence of some independent variables. We used a different design based on data on genetic variation. It is better in terms of reducing and controlling these kinds of variables," commented the lead author of the paper, Dr. Germán D. Carrasquilla. The medic added that the accumulation of abdominal fat due to smoking seems to occur regardless of a person's position in society, alcohol consumption, presence of attention deficit disorder or risk-taking tendencies.

According to the scientists, the reduction of unhealthy fat may be an additional positive effect of smoking cessation. Previously, Korean researchers found that those who quit smoking had a 17% lower risk of developing all types of cancer than current smokers.