Microorganisms detected via breath test linked to body mass, fat accumulation

People whose breath has high concentrations of both hydrogen and methane gases are more likely to have a higher body mass index and percentage of body fat, according to the findings. The combination of the two gases signals the presence of a microorganism that may contribute to obesity.

A person exhales larger amounts of hydrogen and methane gases when a microorganism called Methanobrevibacter smithii (M. smithii) colonizes the digestive tract. Previous research has shown that M. smithii is the predominant organism in the human gastrointestinal tract responsible for methane production.

"Normally, the collection of microorganisms living in the digestive tract is balanced and benefits humans by helping them convert food into energy," said lead author Ruchi Mathur, M.D., director of the Outpatient Diabetes Treatment and Education Center in the Division of Endocrinology at Cedars-Sinai in Los Angeles. "When M. smithii becomes overabundant, however, it may alter the balance in a way that makes the human host more likely to gain weight and accumulate fat."

M. smithii scavenges hydrogen from other microorganisms and uses it to produce methane, which is eventually exhaled. Researchers theorize that the interaction helps hydrogen-producing microorganisms extract nutrients from food more efficiently, which encourages weight gain and obesity in the human host. These microorganisms also may play a role in insulin signaling and regulation.

"This is the first large-scale human study to connect the dots and show an association between gas production and body weight," Mathur said.

The prospective study analyzed the breath content of 792 people. Based on the breath tests, four patterns emerged. The subjects either had normal breath content, higher concentrations of methane, higher levels of hydrogen or higher levels of both gases. The people whose breath test contained higher concentrations of both hydrogen and methane tended to have higher body mass indexes and higher percentages of body fat.

Other researchers working on the study include: M. Amichai, K. Chua, J. Mirocha, G. Barlow and M. Pimentel of Cedars-Sinai Medical Center.