Breath methane concentrations and markers of obesity in patients with functional gastrointestinal disorders.

Background: Obesity is associated with changes in the intestinal microbiome and methane-producing archaea may be involved in energy homeostasis.

Objective: The objective of this article is to investigate the associations between intestinal methane production, waist circumference and body mass index (BMI) as biomarkers for obesity.

Methods: Breath methane and hydrogen concentrations were measured over five hours following fructose or lactose ingestion in 1647 patients with functional gastrointestinal disorders. The relationships between gas concentrations and measures of obesity were investigated by stratifying gas concentration-time profiles by BMI and waist circumference, and, conversely, BMI and waist circumference by peak breath hydrogen and methane concentrations.

Results: Following fructose ingestion, patients with lower BMI and lesser waist circumference had greater breath methane concentrations (all p  < 0.003). Conversely, patients with increased methane concentrations had lower BMI ( p  < 0.001) and waist circumference ( p  = 0.02). After lactose ingestion, BMI and waist circumference were not associated with significant differences in methane. However, greater methane concentrations were associated with a lower BMI ( p  < 0.002), but not with waist circumference.

Conclusion: In this large group of patients mainly negative associations between breath methane concentrations and anthropometric biomarkers of obesity were evident. Studies investigating microbial methane production and energy homoeostasis in different populations are of substantial interest to distinguish epiphenomena from true causality.A follow-up study was registered at Clinical trials.gov NCT02085889.