title: Methane and hydrogen positivity on breath test is associated with greater body mass index and body fat.
abstract: BACKGROUND
  Colonization of the gastrointestinal tract with methanogenic archaea (methanogens) significantly affects host metabolism and weight gain in animal models, and breath methane is associated with a greater body mass index (BMI) among obese human subjects.
  
  
  OBJECTIVE
  The objective of the study was to characterize the relationship between methane and hydrogen on breath test (as a surrogate for colonization with the hydrogen requiring methanogen, Methanobrevibacter smithii), body weight, and percent body fat in a general population cohort.
  
  
  METHODS
  This was a prospective study (n = 792) of consecutive subjects presenting for breath testing.
  
  
  METHODS
  The study was conducted at a tertiary care center.
  
  
  METHODS
  BMI and percent body fat were measured.
  
  
  RESULTS
  Subjects were classified into 4 groups based on breath testing: normal (N) (methane <3 ppm and hydrogen <20 ppm at or before 90 minutes); hydrogen positive only (H+) [methane <3 ppm and hydrogen ≥20 ppm); methane positive only (M+) (methane ≥3 ppm and hydrogen <20 ppm), or methane and hydrogen positive (M+/H+) (methane ≥3 ppm and hydrogen ≥20 ppm]. There were significant differences in age but not in gender across the groups. After controlling for age as a confounding variable, M+/H+ subjects had significantly higher BMI than other groups (N: 24.1 ± 5.2 kg/m(2); H+: 24.2 ± 4.5 kg/m(2); M+: 24.0 ± 3.75 kg/m(2); M+/H+: 26.5 ± 7.1 kg/m(2), P < .02) and also had significantly higher percent body fat (N: 28.3 ± 10.0%; H+: 27.5 ± 9.0%; M+: 28.0 ± 8.9%; M+/H+; 34.1 ± 10.9%, P < .001).
  
  
  CONCLUSIONS
  The presence of both methane and hydrogen on breath testing is associated with increased BMI and percent body fat in humans. We hypothesize that this is due to colonization with the hydrogen-requiring M smithii, which affects nutrient availability for the host and may contribute to weight gain.
authors.affiliation: Division of Endocrine Diabetes and Metabolism, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA. ruchi.mathur@cshs.org
authors.forename: R
authors.initials: R
authors.lastname: Mathur
authors.forename: M
authors.initials: M
authors.lastname: Amichai
authors.forename: K S
authors.initials: KS
authors.lastname: Chua
authors.forename: J
authors.initials: J
authors.lastname: Mirocha
authors.forename: G M
authors.initials: GM
authors.lastname: Barlow
authors.forename: M
authors.initials: M
authors.lastname: Pimentel
mesh_terms: D000273:Adipose Tissue / Q000033:anatomy & histology; D050154:Adiposity / Q000502:physiology*; D000328:Adult; D000368:Aged; D001823:Body Composition / Q000502:physiology; D015992:Body Mass Index; D001944:Breath Tests; D015331:Cohort Studies; D005260:Female; D006801:Humans; D006859:Hydrogen / Q000032:analysis* / Q000378:metabolism; D007792:Lactulose; D008297:Male; D008697:Methane / Q000032:analysis* / Q000378:metabolism; D008875:Middle Aged; D009058:Mouth Breathing / Q000378:metabolism; D009765:Obesity / Q000378:metabolism
chemical_list: D007792:Lactulose; D006859:Hydrogen; D008697:Methane