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Can You Smell Obesity?
By Alice Park
March 27, 2013
21 Comments
According to the latest research, it may be on your
breath.
It turns out that obesity may be detectable as a gas,
thanks to organisms that inhabit our gut. In a study
published in the Journal of Clinical Endocrinology &
Metabolism, researchers extend our knowledge about the
hidden universe of the microbes that live within us to
show that obesity is associated with certain populations
of microbes that give off a distinctive gas.
To be more specific, obesity may smell a lot like…
methane, which is to say, like not much at all, since
methane in its naturally-occurring state is actually
GETTY IMAGES / GETTY IMAGES
man breathing red smoke
odorless. In the study. Dr. Ruchi Mathur, director of
diabetes in the department of medicine at Cedars-Sinai
Medical Center, and her colleagues analyzed the breath of 792
men and women of various ages. Mathur focused on detecting
methane in the breath, since animal studies found that the presence of a certain family of organisms called archaea, which
are older than bacteria and colonize the gut, was linked with weight gain and conveniently released small amounts of
methane gas. Mathur also knew from her own work analyzing the gas makeup of the breath from bariatric surgery patients
that those releasing higher levels of methane in their breath tended to have a body mass index (BMI) nearly 7 points higher
on average than those with lower levels.
(MORE: The Good Bugs: How the Germs in Your Body Keep You Healthy)
And sure enough, Mathur found that among the nearly 800 participants she tested, those with higher levels of methane (3 or
more parts per million over 90 minutes) and hydrogen gases (20 or more parts per million) in their breath also tended to be
heavier, with a BMI about 2.4 points greater than those with normal levels of the gases and about six percent more body fat
on average.
http://healthland.time.com/2013/03/27/can-you-smell-obesity/print/[3/27/2013 10:03:28 AM]
Can You Smell Obesity? | TIME.com
“Our hope is that this is one piece of the complex puzzle that is obesity,” says Mathur, “and that by identifying people who
are obese because they have this microorganism, we can manipulate and work with the gut microbiome to lead to benefits in
weight loss in that subgroup.”
(MORE: What Do Gut Bugs Have to Do With High Cholesterol? A Lot)
The culprit, she believes, is a member of archaea known as Methanobrevibacter smithii, which is present in the intestinal
tract of about 70% of people, but elevated in about 30%. It’s that smaller group of individuals who might be genetically
predisposed to harboring levels of M. smithii that might put them at higher risk of developing obesity. M. smithii harvests
hydrogen molecules from neighboring microbes in the gut, which it then transforms into methane gas. The more it
scavenges hydrogen from its environment, the more other microbes produce. But all of that activity is focused on extracting
energy and nutrients from food, so along with the hydrogen gas, the microbes are also packing in more calories for the host,
which can lead to weight gain. It’s also possible, says Mathur, that the release of methane slows the transit of digested food
through the intestinal tract, and that could increase the time for additional calories from digested food to be absorbed and
added to the body’s tally.
In order for M. smithii to thrive, it needs the hydrogen from surrounding microbes, and that may be why people with higher
levels of both hydrogen and methane gases in their breath were heavier than those with elevated levels of methane or
hydrogen alone.
(MORE: Skim Milk May Not Lower Obesity Risk Among Children)
So how does this help control the obesity epidemic? For those whose weight gain may be due in part to the activity of M.
smithii, controlling the organisms with antibiotics or other medications could slow down the rate at which they pack on the
pounds, and these individuals could easily be identified with a relatively simple breath test.
Mathur and her colleagues are also working with the American Diabetes Association to test a group of people with
prediabetes who are overweight or obese and have elevated levels of methane in their breath. The researchers will test the
participants’ glucose tolerance, the time it takes for digested food to transit through the intestinal tract, and the amount of
calories in the patients’ stool. Then they volunteers will be given an antibiotic to essentially wipe out the population of M.
smithii and the same parameters will be measured again, to see if eliminating the microbes will help change the patient’s
weight profile and alter their trajectory toward diabetes.
She is also studying a group of children to see how early M. smithii buildup occurs, and how soon in development it starts to
set up a pattern of weight gain that might then be interrupted by changing the composition of the gut microbial world.
“From an evolutionary perspective, our relationship with the microorganisms that live in us has basically been symbiotic,
and we have evolved together,” she says. “We’ve had that relationship for millenia, but it is just now being explored and
discovered in more detail.” And, when it comes to controlling the obesity epidemic, could lead to the (sweet?) smell of
success.
MORE: Americans Are Eating Fewer Calories, So Why Are We Still Obese?
Park's latest book is The
http://healthland.time.com/2013/03/27/can-you-smell-obesity/print/[3/27/2013 10:03:28 AM]
Can You Smell Obesity? | TIME.com
Alice Park @aliceparkny
Alice Park is a staff writer at TIME and covers health, medicine, nutrition
and fitness.
http://healthland.time.com/2013/03/27/can-you-smell-obesity/print/[3/27/2013 10:03:28 AM]
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