How’s That Microbiome Working for You in Obesity?

When an idea captures the imagination, it can become something like an ink stain. Tough to alter. One such idea that captured our imagination is the idea that gut microbiota might be a causal factor in obesity. But a new review in Philosophical Transactions of the Royal Society B suggests rethinking this idea. Matthew Dalby asserts that research to date fails to support a role for gut’s microbiome in obesity.

Specifically he concludes:

“With a more critical reading, early studies did not show as large an effect as first appeared and later research, including human trials, has failed to support a role of the gut microbiota in shaping body weight.”

Shaping a Compelling Narrative

Fascination with the microbiome in obesity began with tantalizing observations of links between altered microbiota and the risk of obesity. Myths and misconceptions can grow from such observations and weave together into a compelling narrative. Did you know that microbes outnumber human cells ten to one?! 

With such excitement around a concept, no one cares to hear from naysayers. Dalby explains how this unfolded in the literature on microbiota and obesity:

“Several independent strands of evidence have been explored in the literature, focusing on germ-free mice, whole microbiota transplants, immunological mechanisms and individual bacterial genus. This has given the appearance of a robust area of research with several pillars of support. However, when each strand of evidence is critically examined, it becomes evident that key initial data have often been presented in ways that amplified small effects, single findings have not been later replicated, and key results have been included only in supplementary material. Research showing no effects can be difficult to publish and it remains unknown how many null findings on this topic remain unpublished.”

Critical Thinking Need Not Equal Nihilism

None of this tells us we should discard interest in research for a better understanding of the interaction of microbiota and human obesity. Dalby carefully says his analysis does not refute the possibility of a role for microbiota in obesity.

This is merely a reminder to bring critical thinking to bear whenever someone tells us they they have the key for stopping obesity. Such tidy answers often turn out not to be very enlightening.

Click here for Dalby’s review, here for more on some of the myths of the microbiome, and here for an excellent rationale for being cautious about elegant explanations for obesity.

Sheep, photograph by Azonesa, modified by Radomianin, licensed under CC BY-SA 4.0

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September 5, 2023