Smoking is a rough habit to break – but the benefits of stopping are key to long term health – but some people tend to add pounds which can cause issues.

The damage to the lungs and heart, the smell, the breath are all reasons to quit smoking.  It is a tough habit to break, but critical for long term health. It is a tough journey to get it fully out of the system.  But why do people gain weight after quitting smoking? While people tend to chalk it up as replacing one habit with another, or as an expression of anxiety, a study provides some much-needed scientific explanations.

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Published in the Nature journal, the study suggests that the gut’s microbiome plays a part in the association between quitting smoking and gaining weight. Still, the mechanisms as to why this occurs are not clear.

Scientists devised a variety of tests involving mice, exposing them to smoke and then noting their fluctuations in gut bacteria. The first results showed that mice exposed to cigarette smoke resisted gaining weight when consuming a diet containing high fat. When the smoke was halted and the mice continued to eat the same diet, they gained weight.

Subsequent studies proved gut bacteria’s importance in this situation; scientists provided antibiotics to the mice, depleting their microbiome, and found that it could impact their weight gain. Lastly, scientists transplanted fecal samples of the mice exposed to the smoke towards regular mice, finding that the regular mice experienced weight fluctuations as well.

Researchers then pinpointed the elements in the microbiome responsible for this change, calling out dimethylglycine (DMG) and acetylglycine (ACG) in particular. By enhancing and reducing these elements in mice, they found that even mice who weren’t exposed to smoke experienced weight fluctuations. Healthy mice with DMG supplements gained weight, while healthy mice with ACG supplements lost it.

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Ninety-six human participants also took part in this study, all of whom displayed similar results as the mice. While this isn’t a complete win in terms of understanding how smoke influences our stomachs, it’s a significant first step, one that might help people understand the impact of cigarettes on gut health and might even provide a few solutions in the future that might encourage people to quit the habit without having to worry about the possible side effects.