Can Your Breath Predict Weight Gain?

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A cheeseburger to you is the same as a cheeseburger to me, right? Maybe not. A new study suggests the microorganisms in our gut could affect how efficiently we extract nutrients from food, and the presence of certain bacteria could contribute to obesity for some individuals. And we might not need an invasive procedure to find out what's going on inside: Researchers claim simply analyzing the breath we exhale could point out who's predisposed to obesity.

What It Is

The study, published in the upcoming issue of The Journal of Clinical Endocrinology and Metabolism, analyzed breath readings from 792 people. They found that people with higher concentrations of both hydrogen and methane in their breath were more likely to have higher BMIs and more body fat.

How can this be? Methane production in the gut is normally associated with the proliferation of Methanobrevibacter smithii (try saying that three times fast), a hydrogen-consuming microbe which produces its namesake gas. This gas, in turn, shows up in the air we exhale. The more hydrogen available, the better this methane-producing bacteria does.

But while more hydrogen and more methane likely indicate an excess of gut bacteria — organisms the body needs in moderate amounts for healthy digestive function — it's still unclear exactly how they're contributing to weight gain (or if they're the direct culprits at all). Some researchers speculate that having more of the gas-producing bacteria could help organisms in the gut extract nutrients more efficiently, meaning some people's bodies could be getting more energy from the food they eat — and gaining weight as a result.

It's also been suggested that the presence of methane slows down food in the digestive tract, giving the body more time to extract energy from food. Whatever the cause, researchers are hopeful the findings will give more insight into what happens in our intestines. They're also working to figure out if controlling the bacteria could allow us to better combat obesity.

Is It Legit?

Yes, but maybe not for the obvious reasons. The researchers themselves aren't sure exactly how to interpret these results. As Science Daily reported, lead author Dr. Ruchi Mathur expressed words of caution: "We're only beginning to understand the incredibly complex communities that live inside of us."And while the study's sample size wasn't small by any means (you try asking 792 people to breathe into a test tube), the study didn't control for factors like diet. The researchers also can't rule out the possibility that the bacteria only thrive after a person becomes obese, which would mean the little microbes may not be the main factor in weight gain.

Whatever the underlying cause of human obesity — and it's likely there are a bunch of factors involved — the study does illustrate that gut bacteria definitely has some relationship with weight. We've also known for a while that methane and hydrogen breath tests can be good indicators of gastrointestinal disease [1] [2].

The next phase of research — which Mathur's team is currently working on — is to determine the exact relationship between M. smithii and our metabolism. The next great diet pill might have more to do with the bacteria in our guts than the food we put into them.

Do you think gut bacteria have a role in metabolism? Let us know in the comments below or tweet the author @d_tao.

About the Author
David Tao
I'm the chief research officer for Greatist.com and a greatist since 2011. Originally from Kentucky but now calling NYC home.

Works Cited

  1. Methane production during lactulose breath test is associated with gastrointestinal disease presentation. Pimentel, M., Mayer, A.G., Park, S., et al. GI Motility Program, Cedars-Sinai Medical Center. Dig Dis Sci, 2003 Jan;48(1):86-92.
  2. How to Interpret Hydrogen Breath Tests. Ghoshal, U. Journal of Neurogastroenterology Motility. 2011 July; 17(3): 312-317.

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