Gut colonization with methanobrevibacter smithii is associated with childhood weight development

OBJECTIVE: To prospectively investigate the presence and counts of archaea in feces of 472 children in association with weight development from 6 to 10 years of age. METHODS: Within the KOALA Birth Cohort Study, a single fecal sample from each child was analyzed by quantitative polymerase chain reaction to quantify archaea (Methanobrevibacter smithii, Methanosphera stadtmanae). Anthropometric outcomes (overweight [body mass index {BMI} >/= 85th percentile], age- and sex-standardized BMI, weight, and height z-scores) were repeatedly measured at ages (mean +/- SD) of 6.2 +/- 0.5, 6.8 +/- 0.5, 7.8 +/- 0.5, and 8.8 +/- 0.5 years. Generalized estimating equation was used for statistical analysis while controlling for confounders. RESULTS: Methanobrevibacter smithii colonization was associated with an increased risk of overweight (adjusted odds ratio [OR] = 2.69; 95% confidence interval [CI] 0.96-7.54) from 6 to 10 years of age. Children with high levels (>7 log10 copies/g feces) of this archaeon were at highest risk for overweight (OR = 3.27; 95% CI 1.09-9.83). Moreover, M. smithii colonization was associated with higher weight z-scores (adj. beta 0.18; 95% CI 0.00-0.36), but not with height. For BMI z-scores, the interaction (P = 0.008) between M. smithii and age was statistically significant, implying children colonized with M. smithii had increasing BMI z-scores with age. CONCLUSIONS: Presence and higher counts of M. smithii in the gut of children are associated with higher weight z-scores, higher BMI z-scores, and overweight.