The human gut is home to a vast and complex community of microorganisms, collectively known as the gut microbiome. Rather than existing as a random assortment of species, the bacteria organize themselves into a few distinct, stable communities called “enterotypes” or “gut types.” These classifications are defined by the dominant bacterial genus, suggesting that not all human guts function metabolically in the same way. Understanding enterotypes provides a framework for recognizing how individual differences in microbial composition influence health, diet response, and general well-being.
Identifying the Major Gut Types
The most widely recognized classification system groups the adult human gut microbiome into three enterotypes, named after the most abundant bacterial genus. This stratification is based on the dominant population, which dictates the functional characteristics of the microbial community.
Enterotype 1: Bacteroides
This type is dominated by the genus Bacteroides, which are proficient at breaking down proteins and fats, particularly those derived from animal sources. It is commonly associated with a Western-style diet high in animal protein and saturated fats.
Enterotype 2: Prevotella
This enterotype is characterized by a high abundance of Prevotella, a group of bacteria specializing in degrading complex plant-derived carbohydrates and fiber. Individuals with this enterotype often consume diets rich in complex carbohydrates and fiber, such as those found in agrarian or vegetarian communities.
Enterotype 3: Ruminococcus
This grouping is defined by the dominance of Ruminococcus and related genera, which are also skilled at fermenting resistant starches and cellulose from plant foods. The dominant genera possess distinct enzymatic capabilities, meaning each enterotype is optimized to process specific types of macronutrients.
Environmental and Genetic Influences
The establishment and long-term maintenance of an individual’s enterotype are largely driven by environmental factors, with long-term dietary patterns being the most influential component. The food consumed over years provides the sustained nourishment that selects for the growth of one dominant bacterial community over others. For example, a persistent diet favoring high fiber and complex carbohydrates will promote the expansion of Prevotella or Ruminococcus populations.
The initial colonization of the gut in early life also sets the stage for the mature enterotype. Factors such as the mode of birth and infant feeding establish the foundational community, which remains highly stable throughout adulthood. Although host genetics influence the gut environment, the microbial community’s response to diet often outweighs these inherited factors.
Health Implications of Your Gut Type
The specific bacterial composition of an enterotype has consequences for the host’s metabolism and overall health. The Bacteroides type exhibits a higher capacity for synthesizing the B vitamin biotin (B7), but is also associated with metabolizing dietary choline into the cardiovascular risk factor TMAO. Conversely, the Prevotella enterotype is efficient at producing the B vitamin thiamine (B1) and is better equipped to break down plant fibers.
This metabolic difference affects health outcomes; for example, individuals with the Prevotella type achieve greater weight loss when following a high-fiber, whole-grain diet compared to those with a Bacteroides profile. The Ruminococcus enterotype is noted for generating short-chain fatty acids (SCFAs), such as butyrate, from the fermentation of complex carbohydrates. These SCFAs are a primary energy source for colon cells and contribute to maintaining the gut barrier and reducing inflammation.
The distinct metabolic outputs of each enterotype suggest that a single diet or nutritional recommendation will not yield the same health benefits for every person. The enterotype acts as a functional filter, determining how efficiently a person can extract specific nutrients or protective compounds from their food.
Can Gut Types Be Changed
The question of whether an adult can fundamentally shift their enterotype is a topic of scientific investigation. The enterotype is characterized by a high degree of resilience, meaning the microbial community reverts to its original state following short-term disturbances. Even significant, short-term dietary changes or antibiotic courses may cause temporary shifts, but they often fail to dislodge the dominant genus that defines the enterotype.
A permanent transition from one enterotype to another, such as switching from Bacteroides to Prevotella dominance, requires sustained and long-term dietary intervention. It is difficult to fundamentally alter this core microbial structure in adulthood because the resident microbes have established a stable, co-dependent network. While the enterotype’s stability is high, temporary microbial shifts can still be beneficial, allowing for targeted, short-term health improvements.