Quit-Smoking Weight Gain Owed To Change in Gut Bacteria


It is common knowledge that people who quit smoking tend to gain weight, presumably because they substitute eating food for cigarettes. Yet, many who quit smoking and gain weight report they do not eat more than when they smoked.

Now, we all have reason to believe they are telling the truth. It seems that people quit smoking and put on pounds because of a shift in their intestinal flora, not increased caloric intake. This is what researchers at Zurich University Hospital have discovered.

Interesting, But Eww!

Gerhard Rogler and his colleagues examined four stool samples from each of their study participants over a nine week period. They studied the genetic material of intestinal bacteria found in the samples. Of the 20 study subjects, five were non-smokers, five smoked, and 10 of them quit smoking one week after the study began.

What the Samples Revealed

  1. The fecal bacteria diversity of the smokers and non-smokers changed very little over the course of the study.
  2. The microbial intestinal and fecal residents of those who quit smoking altered significantly.
  3. You may be horrified to know that in the samples of those who quit smoking, Fimicutes and Actinobacteria intestinal representatives diminished as the presence of Proteobacteria and Bacteroidetes factions grew.
  4. Those participants who quit smoking gained significant weight, even though their drinking and eating habits did not change.

The bacterial strains that increased in the intestines of those who discontinued smoking are the same as those known to thrive in the gut flora of obese people.

The Mixed Blessing of Efficiency

Rogler’s study mirrors similar studies conducted with mice, although the previous studies did not involve mice who quit smoking. Rather, researchers implanted the feces of obese mice into the intestines of average-weight mice. The Proteobacteria and Bacteroidetes flora increased in the average-sized mice and so did their weight.

It seems that Proteobacteria and Bacteroidetes, those found in obese people and those who quit smoking, are more efficient at using the energy of ingested food, resulting in weight gain. So, when individuals stop smoking and their gut flora shifts to the more efficient type, they are likely to put on weight even if they eat as before.

While this knowledge does not help those who quit smoking keep the pounds off, it at least helps explain the weight gain phenomenon. It may also provide some solace to those who quit smoking, maintain a healthy diet, and still feel their clothes getting tighter.

Source: Science Daily

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