title: Intestinal methane production in obese individuals is associated with a higher body mass index.
abstract: BACKGROUND
  Obesity is an epidemic that affects 1 in 3 individuals in the United States, and recent evidence suggests that enteric microbiota may play a significant role in the development of obesity. This study evaluated the association between methanogenic archaea and obesity in human subjects.
  
  
  METHODS
  Subjects with a body mass index (BMI) of 30 kg/m² or higher were prospectively recruited from the weight loss program of a tertiary care medical center. Subjects who met the study's inclusion criteria were asked to complete a questionnaire that included a series of visual analogue scores for bowel symptom severities. Subjects then provided a single end-expiratory breath sample to quantitate methane levels. Bivariate and multivariate analyses were used to determine associations with BMI.
  
  
  RESULTS
  A total of 58 patients qualified for enrollment. Twenty percent of patients (n = 12) had breath test results that were positive for methane (>3 parts per million [ppm]), with a mean breath methane concentration of 12.2±3.1 ppm. BMI was significantly higher in methane-positive subjects (45.2±2.3 kg/m²) than in methane-negative subjects (38.5±0.8 kg/m²; P=.001). Methane-positive subjects also had a greater severity of constipation than methane-negative subjects (21.3±6.4 vs 9.5±2.4; P=.043). Multiple regression analysis illustrated a significant association between BMI and methane, constipation, and antidepressant use. However, methane remained an independent predictor of elevated BMI when controlling for antidepressant use (P<.001) and when controlling for both constipation and antidepressant use (6.55 kg/m² greater BMI; P=.003).
  
  
  CONCLUSIONS
  This is the first human study to demonstrate that a higher concentration of methane detected by breath testing is a predictor of significantly greater obesity in overweight subjects.
authors.affiliation: GI Motility Program, Cedars-Sinai Medical Center, Los Angeles, California, USA.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Basseri
authors.forename: Benjamin
authors.initials: B
authors.lastname: Basseri
authors.forename: Mark
authors.initials: M
authors.lastname: Pimentel
authors.forename: Kelly
authors.initials: K
authors.lastname: Chong
authors.forename: Adrienne
authors.initials: A
authors.lastname: Youdim
authors.forename: Kimberly
authors.initials: K
authors.lastname: Low
authors.forename: Laura
authors.initials: L
authors.lastname: Hwang
authors.forename: Edy
authors.initials: E
authors.lastname: Soffer
authors.forename: Christopher
authors.initials: C
authors.lastname: Chang
authors.forename: Ruchi
authors.initials: R
authors.lastname: Mathur