Can a Healthy Gut Help Solve the Obesity Epidemic?

The gut microbiome has become a popular topic among the general public. In response, multiple microbiome-targeted foods, supplements, and even beauty products have hit retailers' shelves.

But is there clinical evidence that the gut microbiome is a causal driver of obesity? And if it is, what is the best way to target it to elicit health benefits?

Karen D. Corbin, PhD, RD

The physiologic impact of the gut microbiome is key to deciphering its potential benefits for human health. The term "gut microbiota" refers to the bacteria, yeast, fungi, viruses, and bacteriophages that inhabit the human colon. The term "gut microbiome" is similar but refers to the genetic makeup of those organisms. Bacteria greatly outnumber other microbes in the gut and are the most well studied in response to human phenotypes (Ursell et al; Berg et al).

As far as the various types of products your patients might encounter, there are three main types. Probiotics contain live microorganisms that may provide health benefits. Prebiotics are foods that reach the gut microbiota and can be utilized by those microorganisms. Postbiotics refers to metabolites secreted by microorganisms that are known to have a physiologic impact.

The products are everywhere, your patients are encountering them, but what does the science say? Multiple lines of evidence show the functional impact of the gut microbiome on fundamental processes such as immunity, inflammation, and glycemic control. Evidence also suggests that a key driver of gut microbiome dysfunction, and potentially of human disease, is the scarcity of dietary substrates reaching the colon when people consume diets lacking in fiber and resistant starch (very common in Western countries). In such a scenario, the gut microbes are essentially "starved" and turn to alternative pathways to survive, often at the detriment of the human host.

Given the key role of the gut microbiome in human health, and particularly in energy metabolism, it makes sense that the evidence has converged to reveal a relationship between the gut microbiome and obesity. When it comes to the causal relationship between the gut microbiome and obesity, the strongest available evidence has emerged from rodent models where it has been demonstrated that fecal microbiota transplantation can transfer the obese phenotype and that the gut microbiome plays a fundamental role in harvesting energy from the diet.

In humans, most data have been associational in nature, with studies demonstrating different microbial signatures in people with obesity and in response to weight loss. A recent controlled feeding study found that varying the amount of dietary energy that people consume is associated with changes in the gut microbiome, demonstrating the intricate relationship between the host, diet, and microbes.

What remains to be determined is whether the associations uncovered between the gut microbiome and body weight are causal or whether the gut microbiome is simply a reflection of the human host's health.

A deeper dive into precisely how microbes and diet interact to affect human weight regulation is key to developing precision nutrition approaches. Until those discoveries are made, our current understanding suggests that "feeding" the gut microbes through diets that have plentiful substrates (such as fiber) could confer a benefit to patients looking to manage their weight and improve the health of their gut (and themselves).

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Cite this: Can a Healthy Gut Help Solve the Obesity Epidemic? - Medscape - Jun 28, 2023.