The secret to perfect muscle growth? A healthy gut microbiome

Estimated reading time: 2:51 min.

This article is verified by 2 studies/publications.

Scientific research has increasingly focused on the gut microbiome in recent years, revealing its direct and indirect influence on various bodily processes. An imbalanced gut flora has been associated with numerous diseases.

A recent study showed[1] that the gut microbiome’s impact on the body is even more complex than previously thought. In this study, conducted on mice, researchers were able to demonstrate that an imbalanced gut microbiome can impair skeletal muscle adaptation to exercise, affecting muscle growth after strength training.

Previous research has already explored the relationship between the microbiome[2] and muscle mass, with some suggesting that changes in the gut microbiome could contribute to age-related decreases in muscle mass. This is also practically reflected in the fact that the recommendation for daily protein intake increases with age.

Too long; didn’t read (Summary)

  • A study using mice investigated the potential impact of the gut microbiome on muscle growth.
  • The mice were provided with running wheels containing small weights to simulate strength training and encourage muscle growth.
  • Half of the mice were administered antibiotics to reduce their gut bacteria.
  • Comparison of muscle size and muscle fibers revealed that mice with an intact microbiome had greater muscle growth overall.
  • While the exact cause of this effect is unclear, the study suggests that the microbiome likely plays a role in influencing muscle growth.

Testing on mice

The aforementioned study revisited the topic and investigated it directly – but only in mice for now.

How do you test strength training on mice? For half of the mice, the running wheel was equipped with small additional weights, which were progressively increased over the course of 8 weeks. The maximum of these additional weights was about one-third of the mice’s body weight. Classic strength training.

Half of the mice were given water mixed with antibiotics, which is known to severely deplete the gut flora – in humans as well.

Gut dysbiosis inhibits muscle growth after training

In the end, the researchers compared both muscle size and the type of muscle fibers. In short: The study showed that mice need an intact microbiome for their muscles to grow after strength training.

Specifically, it was found that the Type-1 muscle fibers in the antibiotic group did not grow as much as in the group whose microbiome remained intact. The growth of Type-2 muscle fibers was also impaired.

However, it remains unclear exactly how the lack of diversity in gut bacteria inhibits muscle growth. It is speculated that perhaps a substance, which is usually produced by the gut bacteria, stimulates or at least positively influences muscle growth. Or that the antibiotics themselves would have a direct negative effect on growth, for example, by promoting inflammation through weakening the gut barrier. But the researchers ultimately found no evidence for this.

In the other study mentioned earlier, it is suspected that the higher protein requirement for older people to maintain muscle mass may be due to proteins being absorbed less efficiently due to age-related changes in the microbiome.

Healthy gut – healthy muscle growth

This mouse study adds to the evidence suggesting that a healthy microbiome is beneficial for muscle growth. However, since not all research results obtained from mouse models can be directly applied to humans, and many other factors can influence the study results, there is no definitive answer to the suspected connection between gut health and muscle growth.

Nevertheless, this study once again demonstrates the importance of the diversity of gut bacteria. A varied and healthy diet should therefore receive adequate attention even when focusing on strength training.


  1. Dysbiosis of the gut microbiome impairs mouse skeletal muscle adaptation to exercise. Taylor R. Valentino, Ivan J. Vechetti Jr, C. Brooks Mobley, Cory M. Dungan, Lesley Golden, Jensen Goh, John J. McCarthy. The Journal of Physiology. 2021. Volume 599, Issue21, Pages 4845-4863. doi: 10.1113/JP281788
  2. Dietary Protein and Muscle in Aging People: The Potential Role of the Gut Microbiome. Ni Lochlainn M, Bowyer RCE, Steves CJ. Nutrients. 2018 Jul 20;10(7):929. doi: 10.3390/nu10070929. PMID: 30036990; PMCID: PMC6073774.

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