Abstract
Obesity is a disease with a complex etiology and variable prevalence across different populations. While several studies have reported gut microbiota composition differences associated with obesity in humans, there has been a lack of consistency in the nature of the reported changes; it has been difficult to determine whether methodological differences between studies, underlying differences in the populations studied, or other factors are responsible for this discordance. Here we use 16 S rRNA data from previously published studies to explore how the gut microbiota-obesity relationship varies across heterogeneous Western populations, focusing mainly on the relationship between (1) alpha diversity and (2) Prevotella relative abundance with BMI. We provide evidence that the relationship between lower alpha diversity and higher BMI may be most consistent in non-Hispanic white (NHW) populations and/or those with high socioeconomic status, while the relationship between higher Prevotella relative abundance and BMI may be stronger among black and Hispanic populations. We further examine how diet may impact these relationships. This work suggests that gut microbiota phenotypes of obesity may differ with race/ethnicity or its correlates, such as dietary components or socioeconomic status. However, microbiome cohorts are often too small to study complex interaction effects and non-white individuals are greatly underrepresented, creating substantial challenges to understanding population-level patterns in the microbiome-obesity relationship. Further study of how population heterogeneity influences the relationship between the gut microbiota and obesity is warranted.
Highlights
Obesity has reached epidemic proportions in Western populations.[1]
One small study found that morbidly obese individuals had increased relative abundance of Prevotella,[14] and Prevotella relative abundance positively correlated with BMI in a cohort of HIV positive individuals and controls in Mexico City,[15] but Prevotella dominated communities were explicitly found to not correlate with Body Mass Index (BMI) in the Old Order Amish.[2]
We first observed that there may be distinct gut microbiota phenotypes associated with obesity while performing a metaanalysis that combined 16 S ribosomal RNA data from Obese Twins[4] and the GG study[19] (Supplementary Fig. 1)
Summary
Obesity has reached epidemic proportions in Western populations.[1]. Studies aiming to determine the cause of this precipitous increase are complicated by the mixed etiology and manifestations of the disease. The ratio of Bacteroidetes to Firmicutes in obese versus lean humans has been reported to decrease to increase or to not change at all.[5] one small study found that morbidly obese individuals had increased relative abundance of Prevotella,[14] and Prevotella relative abundance positively correlated with BMI in a cohort of HIV positive individuals and controls in Mexico City,[15] but Prevotella dominated communities were explicitly found to not correlate with Body Mass Index (BMI) in the Old Order Amish.[2] These inconsistencies may be influenced by methodological differences between studies,[16] by differences in composition that are not readily captured by the current technologies, or they may reflect that genetic, environmental, and/or lifestyle heterogeneity across the surveyed populations has an influence on the nature of the microbial associations that occur with obesity and related metabolic conditions.[5] These influences are poorly understood both in terms of effects on the gut microbiota composition overall and in the context of the diseasespecific relationships.[17,18]
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