Gut microbe levels and obesity, part 2

After Monday’s post on the gut microbiota, I found a study from a few weeks ago that links exercise and microbiota diversity.  Specifically, the authors found that athletes in their study had greater diversity of gut microbe species than controls, suggesting that they have better digestion and metabolism.  The authors compared the diet and exercise of male rugby players to a sample of controls.  Their main results included:

  • Athletes had higher levels of plasma creatine kinase, a biomarker for exercise, than controls
  • The gut microbiota of athletes was more diverse than that of controls, and diversity was correlated with creatine kinase levels
  • Athletes’ diets were comprised of more protein and supplements than controls, and gut microbiota diversity was correlated with protein intake

So exercise is good for our gut?  Not necessarily.  Diet and exercise go hand in hand.  In this case, athletes had both increased creatine kinase and increased protein consumption, and both were correlated with microbial diversity.  It has been shown before that diet directly affects microbiota diversity, but from this study we can’t pick apart the causal relationship between these three things.  To say that exercise has an impact on diversity suggests that the first diagram below is the causal model, but really it could be any of the three, or a more complicated one entirely.dagitty-model-2dagitty-model-4 dagitty-model-3

Fortunately, the authors acknowledge this limitation:

Further, intervention-based studies to tease apart this relationship will be important and provide further insights into optimal therapies to influence the gut microbiota and its relationship with health and disease.

It will be interesting to follow this lead.  In the mean time, go for a run.

Causal diagrams were made with DAGitty v2.0

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