Human gut microbes associated with obesity

Our gut microbes do us a service by performing metabolic chores that we have not evolved to do for ourselves. In a sense their genes are part of the 'metagenome' that is Homo sapiens. That is illustrated by two related papers in this issue that present evidence for a microbial component to obesity. A study of the abundance of the two dominant groups of bacteria in the gut of obese individuals shows that increased numbers of Bacteroidetes bacteria correlate with weight loss. And a study of genetically obese mice reveals that their gut microbial community has a greater capacity for harvesting energy than that of lean littermates: the trait is transmissible by transplanting the community into germ-free mice. This work suggests that the gut microbiome associated with obesity might be a biomarker and possibly a therapeutic target.