Association between breath methane concentration and visceral fat area: a population-based cross-sectional study

High visceral fat area (VFA) is a stronger predictor of cardiovascular disease and overall mortality, compared with body mass index (BMI) and waist circumference (WC). Recent reports demonstrate that obesity is related to breath gas, which is produced by the intestinal microflora. However, these studies define obesity using BMI, not VFA. In this population-based cross-sectional study, we investigated the relationship between breath gases (methane and hydrogen) and both VFA and BMI. A total of 1033 participants (62% women; age [mean standard deviation] 54.4 14.9 years) in the 2015 Iwaki Health Promotion Project in Japan were enrolled in the study. Breath samples were collected using a breath bag and analyzed by gas chromatography. VFA was measured using a visceral fat meter. The proportion of methanogenic bacteria to total intestinal microbiota was measured by polymerase chain reaction and 16S rRNA gene sequencing analysis. Our analysis revealed a significant association between high VFA and low breath methane, even after adjusting for confounding factors (B = -0.024 and P = 0.004). To identify the association between breath methane and VFA in participants with methane-producing bacteria in their intestinal microflora, participants were divided into two groups based on the presence or absence of methanogenic bacteria in their stool. The Methanogen + group was further divided into two subgroups with breath methane higher (Methane-UP) or lower (Methane-LO) than the median breath methane concentration. VFA was significantly lower in the Methane-UP group than in the Methane-LO group. In participants with methanogenic bacteria, breath methane concentration might be an independent biomarker of visceral fat accumulation.