Figure 41.1: Genetics and Diet Affect the Composition of the Gut Microbial Community (A) The closer the genetic relationship between two people, the more similar their gut microbial communities are. (B) Obese people have proportionally more bacteria in the phylum Firmicutes, and proportionally fewer bacteria in the phylum Bacteroidetes, than do lean people. However, the microbial community of obese people approaches that of lean people as they lose weight on a calorie-restricted diet. Error bars indicate 1 standard error from the mean in both (A) and (B) (see Appendix B).