How Fit You Are May Depend On The Bacteria in Your Gut Interview with:

James R. Bagley, PhD Assistant Professor of Kinesiology Director, Muscle Physiology Lab Co-Director, Exercise Physiology Lab Research Director, Strength & Conditioning Lab San Francisco State University

Dr. Bagley

James R. Bagley, PhD
Assistant Professor of Kinesiology
Director, Muscle Physiology Lab
Co-Director, Exercise Physiology Lab
Research Director, Strength & Conditioning Lab
San Francisco State University What is the background for this study? What are the main findings?

Response: The human body contains many billions of bacteria cells, and the type of bacteria in your gastrointestinal tract (termed gut microbiota) has been linked to certain diseases.

Most of your gut microbiota falls into two categories: Firmicutes (F) or Bacteroidetes (B). The relative gut F/B ratio has been used to assess microbiota health. Our study was the first to examine potential relationships among F/B ratio and cardiorespiratory fitness, body composition, and diet in healthy young men and women

We recruited 37 healthy adults to undergo a battery of physiological tests and collected stool samples to analyze their gut F/B ratio using qPCR.

We found that F/B ratio was significantly correlated with cardiorespiratory fitness, but with no other variables. In fact, this correlation was so strong that a person’s fitness level explained ~22% of the variance in their gut bacteria composition. What should readers take away from your report?

Response: Our human data supports previous evidence in animal models that a strong relationship exists between relative gut microbiota composition and physical fitness. This shows that gut bacteria is likely important for regulating many physiological processes that are currently not well understood.

It should also be mentioned that our data was collected in a “free-living environment” and not a randomized control trial, therefore we cannot establish causation. That is, we do not know if the relationship found here was caused by exercise training or if the observed F/B ratio actually pre-disposed someone to achieve higher levels of physical fitness. What recommendations do you have for future research as a result of this work?

Response: Future studies should continue where we left off and conduct exercise training studies in healthy adults to determine:

1) If exercise training alters gut microbiota composition,

2) What types of training (e.g., aerobic, strength, etc.) alter the gut microbiota, and

3) To what extent the gut microbiota affects health/performance measures after training.

This research on the gut microbiome is so new and I believe that we are just starting to scratch the surface here… Is there anything else you would like to add?

Response: As I stated, the field of microbiome research and human health is wide open! We are still at the beginning and I’d like to invite young researchers out there to consider studying in this filed. If you are interested in advancing human health & medicine, investigating the relationship between humans and our microbiome is a great place to be. Let’s keep moving the field forward!

I would like to acknowledge that our project was led by SF State graduate student Mr. Ryan Durk. This was the product of a fruitful collaboration among our lab in Kinesiology at SF State, the Health Equity Research Lab (Dr. Leticia Márquez-Magaña, and Georgia Southern University (Dr. Gregory Grosicki).


Ryan P. Durk, Esperanza Castillo, Leticia Márquez-Magaña, Gregory J. Grosicki, Nicole D. Bolter, C. Matthew Lee, James R. Bagley.Gut Microbiota Composition is Related to Cardiorespiratory Fitness in Healthy Young AdultsInternational Journal of Sport Nutrition and Exercise Metabolism, 2018; 1 DOI: 10.1123/ijsnem.2018-0024 

Jul 12, 2018 @ 4:30 pm




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