The review – which gathered data from 50 studies from ten different European countries, Japan, the US and Australia published between 1990 and 2012 – looked at the impact of treatment of the stomach bacteria Helicobacter pylori (H. pylori), which can cause stomach ulcers. It suggested a correlation between prevalence rates of H. pylori and and weight gain in developed countries.
Professor Gerald Holtmann from the department of gastroenterology and hepatology at the Princess Alexandra Hospital in Australia, who led the review, said: “The rate of obesity and overweight were inversely and significantly correlated with the prevalence of H. pylori infection.”
“The gradual decrease of the H. pylori colonisation observed in recent decades could be causally related to the obesity endemic observed in the Western world,” he said.
However the researchers said that other factors linked to H. pylori aside from infection could also explain this association with obesity. "Thus the role that the gastrointestinal microbiome may play needs to be properly addressed. It is well established that there is an interplay between diet, microbiome and health," they wrote.
An emerging debate
The review, published in Alimentary Pharmacology & Therapeutics, followed what it called an “emerging debate” over the affect of H. pylori infection on body mass index (BMI).
Of the reviewed studies, the mean H. pylori rate was 44.1%, with a range of 17–75%, while the average rates for obesity and the overweight were 46.6% and 14.2%, respectively. The results suggested an inverse, significant correlation between these two data sets.
According to the researchers, 50% of the global population may be infected with H. pylori, but only 20% of this group experience symptoms. If symptoms do occur, they may be that of peptic ulcer disease which can mean fullness, bloating, early satiety and nausea.
The researchers said while it was possible to speculate weight gain was due to the clear-up of these satiety symptoms, well-controlled studies included in the review meant this was unlikely. They suggested that the correlation could instead be due to an increase in the hunger hormone, ghrelin.
“Interestingly, in one study, plasma ghrelin increased profoundly in asymptomatic subjects after H. pylori cure.This could lead to increased appetite and consequently weight gain, and contribute to the increasing obesity seen in Western populations where H. pylori prevalence is low,” they wrote.
The researchers adjusted to account for gross domestic product of the subjects, which they said ruled out the possibility that the association was simply mediated by the income or the development status of the populations included in the analysis.
Studies focusing on non-random samples or patient cohorts with H. pylori-associated diseases were excluded from the review.
Source: Alimentary Pharmacology & Therapeutics
Published online ahead of print, doi: 10.1111/apt.12790
'Review article: associations between Helicobacter pylori and obesity - an ecological study'
N. Lender, N. J. Talley, P. Enck, S. Haag, S. Zipfel, M. Morrison, G. J. Holtmann