According to the findings, results from a standard breath test used to assess bacterial overgrowth in the gut can also tell doctors if you have a high percentage of body fat.
The microbiome, or the trillions of good and bad bugs that line your gut, can get out of balance. When bad bacteria overwhelm good bacteria, symptoms such as bloating, constipation and diarrhea may occur. The new study, appearing in the Journal of Clinical Endocrinology & Metabolism, suggests that this scenario may also set someone up for obesity.
How the study was done
For the study, individuals drank a sugary lactulose syrup. Breath samples were then collected every 15 minutes for two hours. Participants also had their body fat measured in two ways. One was body mass index (BMI), which takes height and weight into account. The other method uses low-wattage electrical conductivity, which differentiates between lean and fatty tissue.
Those participants whose breath samples showed higher levels of two gases -- methane and hydrogen -- had higher BMIs and more body fat than participants who had normal breath or a higher concentration of only one of the two gases, the study showed. This pattern suggests that the gut is loaded with a bug called Methanobrevibacter smithii, the researchers explained.
It's possible that when this type of bacteria takes over, people may be more likely to gain weight and accumulate fat, said lead study author Dr. Ruchi Mathur, director of the outpatient diabetes treatment center at Cedars-Sinai Medical Center in Los Angeles.
Although there are other ways to measure body fat and BMI, the researchers suggested that individuals with higher methane and hydrogen content in their breath may be more likely to respond to specific weight loss methods down the line. "Obesity is not a one-size-fits-all disease," Mathur said.
If the study findings are confirmed, certain weight-loss treatments could be matched to people who have this breath pattern. One possibility, for instance, might be that probiotics, which help restore and maintain the natural balance of organisms in the gut, could have a role in treating or preventing obesity.
But the science is not there yet, experts cautioned.
Bacteria and BMI
"This is an important study looking at bacteria in the intestine and how they are related to BMI," said Dr. Spyros Mezitis, an endocrinologist at Lenox Hill Hospital in New York City. "The more methane and hydrogen in the breath, the higher the body fat." But, "we need more studies to figure out how bacteria is related to the growing obesity epidemic and what happens if we modify it," Mezitis said.
It's way too soon to start thinking about probiotics as a treatment for obesity, said Dr. Peter Green, director of the Celiac Disease Center at Columbia University Medical Center, in New York City. Green routinely uses breath testing to assess individuals with gastrointestinal issues such as bloating, diarrhea and constipation. "Some people with bacterial overgrowth in their gut have symptoms, but others do not and we are not sure why. The significance of the test results is not always quite clear," he said.
"More research is needed to really define the role of bacterial overgrowth in all of these different conditions," Green said. "It is an exciting area of research, but testing breath to measure body fat is not ready for prime time."
Another expert discussed implications of the new research.
This study adds to the growing evidence that breath tests can provide information about our health, said Dr. Raed Dweik, a pulmonologist at the Cleveland Clinic. "The argument that the authors make is that if we change the bacteria in the gut, we may change obesity and these people will not gain weight as easily," he said. "If we modify the bacteria in the gut, they may lose weight faster or easier."
The next step is to figure out how, or even if, this is possible, said Dweik, who on March 25 had his own study published on the use of breath testing to uncover heart disease risk.
What is your body mass index? Find out by using the U.S. National Institute of Health's BMI calculator.