Does H pylori Eradication Explain Rising Obesity?

Lara C. Pullen, PhD

June 09, 2014

The decline in Helicobacter pylori infection in the Western world over the past few decades may be at least partly responsible for the increased prevalence of obesity in those countries, a new meta-analysis suggests.

As H pylori has been eradicated in developed nations — current figures suggest that fewer than 50% of adults in the United States are currently infected with the bacteria — there has been a concomitant increase in overweight and obesity, Nele Lender of Princess Alexandra Hospital in Woolloongabba, Australia, and colleagues note in their paper, published online May 15 in Alimentary Pharmacology & Therapeutics.

They searched the literature for studies reporting on H pylori and obesity prevalence rates in random population samples of more than 100 subjects and discovered there was an inverse correlation between prevalence of the bacteria and rate of overweight/obesity in countries of the developed world.

Asked to comment on these findings, Martin J. Blaser, MD, director, human microbiome program, New York University Langone Medical Center, New York City, who was not involved with the research, said he is not surprised.

"Bottom line — [H pylori] may have benefit as well as cost — a point that I have been making since 1996; in 1998 [BMJ. 1998;316: 1507-1510], I predicted that doctors of the future will be giving H pylori back to children. We should not be so fast in eradicating H pylori, especially from children," he told Medscape Medical News.

But the Australian researchers caution that further studies are needed before their theory can be confirmed.

"While our data may suggest that the decrease in H pylori prevalence observed in many countries in recent decades could be a contributing factor to the obesity endemic of the Western world, our study cannot rule out that other factors that are correlated with the risk of a H pylori infection are causal for the observed association," they point out.

H pylori Eradication Doesn't Explain Obesity in Developing Nations

The researchers explain that previous controlled trials have shown that, following successful H pylori eradication, patients experience a significant increase in weight.

Although the weight gain could be the result of improved postprandial symptoms in individuals treated for H pylori infection, it's also possible that a more complex relationship exists, they note.

In their review, they used gross domestic product as a determinant of development status and included only studies conducted in countries with a GDP per capita of greater than US $25,000.

They identified 49 studies with data from 10 European nations, Japan, the United States, and Australia. The mean H pylori infection rate was 44.1% (range, 17%–75%), and the mean rates for obesity and overweight were 46.6% and 14.2%.

The rate of obesity and overweight were inversely and significantly (r = 0.29, P < 0.001) correlated with the prevalence of H pylori infection.

"The gradual decrease of the H pylori colonization that has been observed in recent decades (or factors associated with its decrease) could be causally related to the obesity endemic observed in the Western world," they propose.

However, there is an alternative explanation — the possibility that hygiene factors that favor a high H pylori prevalence may also have a protective effect against obesity, they add.

And they acknowledge that, while their work focused on developed countries, an obesity epidemic is also taking place in developing countries, with the latter unlikely to be driven by the eradication of H pylori.

The authors report no relevant financial relationships. Dr. Blaser is the author of the book Missing Microbes.

Aliment Pharmacol Ther. 2014;40:24-31. Article

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