The mix of microbes living in the human gut -- in particular, the presence of a particular bacterium that gobbles hydrogen and produces methane -- may be related to obesity, researchers at Cedars-Sinai Medical Center in Los Angeles said Tuesday.
In a study led by Dr. Ruchi Mathur, head of the Diabetes Outpatient Treatment and Education Center in the hospital's endocrinology division, researchers at Cedars-Sinai recruited 792 people of varying ages, body mass index levels and body fat content and asked them to breathe into a device that analyzed the contents of their breath.
The scientists then looked to see whether the level of methane in the participants' breath correlated with any differences in body fat and BMI. They found that the 28 people who exhaled more methane and more hydrogen had higher body mass indexes and percentages of body fat than other participants with "normal" levels of the gases in their breath, or elevated amounts of just one or the other.
The scientists suggested that the higher levels of hydrogen and methane were a sign that subjects had an overabundance of the bacterium Methanobrevibacter smithii. The bug is thought to increase availability of calories for its host, either through its effect on the hydrogen-producing microbes it feeds off or by slowing the movement of nutrients through the body.