Updated on 2 September 2013
The team noticed that over the study period, the people who had quit smoking also gained an average of 2.2 kilos, even though they insisted that their eating and drinking habits were unchanged
Singapore: A new study conducted by researchers at the Zurich University Hospital has shown that quitting smoking leads to an average weight gain of four to five kilograms in the first year.
Researchers now have evidence that it is the bacterial shift in the intestines that gets former smokers to bulk up after they have quit smoking.
Supported by the Swiss National Science Foundation and published in peer-reviewed scientific journal PLoS One, the study found that when a person stops smoking, the diversity of bacterial strains in their intestines shifts, which closely resembles the gut flora found in people with obesity.
Professor Gerhard Rogler said that his team discovered that, "A change in the composition of the intestinal flora among smokers who quit smoking is another possible reason that even those who cut back on calorie intake after quitting smoking tend to gain weight."
Both recent non-smokers and obese people tend to have more that two bacteria types, Proteobacteria and Bacteroidetes, Professor Rogler explained. "These germs are believed to use energy more efficiently and break down otherwise indigestible fibres and as a result, more of what the person eats is transformed into fat rather than excreted as waste," he said.