Methane-Producing Gut Organism May Promote Weight Gain

Marlene Busko

April 08, 2013

In a study of almost 800 people with gastrointestinal (GI) symptoms, those with high levels of both hydrogen and methane gases in their breath had a higher average body mass index (BMI) and percentage of body fat than their peers.

According to the researchers, having both methane and hydrogen in the breath indicates the presence of Methanobrevibacter smithii in the gut. M smithii, the predominant methane-producing organism in the human gut, also scavenges hydrogen from other microbes, and these 2 actions appear to increase nutrient absorption and promote weight gain.

However, "these are very early studies, [and] this is just one piece of the obesity puzzle," Ruchi Mathur, MD, from Cedars-Sinai Medical Center, in Los Angeles, California, told Medscape Medical News. "We don't think that obesity is 'one size fits all.' We think that there are many...contributing factors."

In the same way as clinicians currently identify type 1 and type 2 diabetes, "50 years from now we might have a type 1, 2, 3, and 4 obesity, some of which might respond to different treatments," she added.

The study was published online on March 26 in the Journal of Clinical Endocrinology & Metabolism.

The researchers recently published a study showing that obese individuals who had a positive breath test for methane also had a BMI that was, on average, almost 7 points higher than their peers (Basseri RJ et al. Gastroenterol Hepatol. 2012;8:22-28).

May Allow More Calories to Be Extracted From Food?

To investigate this relationship in a population with a range of body weights, they enrolled consecutive subjects presenting at a GI clinic with symptoms of bloating (61% of patients), abdominal pain (48%), constipation (42%), or diarrhea (35%). The subjects had a mean age of 47 years, and 71% were women.

They were divided into 4 groups based on their breath tests: normal (<3 ppm methane and <20 ppm hydrogen at 90 minutes or earlier), positive for methane only, positive for hydrogen only, or positive for both gases.

Compared with subjects in the other 3 groups, those in the group with positive breath tests for both gases had a significantly higher average BMI (26.5 vs about 24 kg/m2) and average percentage of body fat (34.1% vs about 28%).

M smithii are not bacteria; rather, they are archaea, which live in the human gut, as part of the up to 1012 microbes there, Dr. Mathur noted.

The finding that a positive breath test for both hydrogen and methane was linked to higher body fat and BMI supports the current hypothesis for M smithii's role in the gut. "Our assumption is when you have this milieu in the absorptive part of the intestine you can extract more calories from food," Dr. Mathur said.

"In individuals who have methane-positive breath, who harbor this particular organism — M smithii — perhaps eradicating that organism may actually benefit them in their goal to reach metabolic optimization; it certainly isn't going to apply to everybody," she added.

The group is currently studying the impact of giving a short course of targeted antibiotics to obese subjects who have a positive breath methane test.

The authors have disclosed no relevant financial relationships.

J Clin Endocrinol Metab. 2013. Published online March 26, 2013. Abstract